The underground ecosystem

complex and under-appreciated

The ground: we stomp all over it, dig holes in it for buildings and alien plants, scrape it off and discard it for access to minerals. That’s the meaning of being ‘treated like dirt’.

Nevertheless, a lot goes on underground in the layers of soil. It’s a very complex ecosystem. Sometimes called the rhizosphere, it’s the realm of roots.

This essay includes several topics that have appeared here before, but this time I’ll try to bring them together, if briefly, in one context, while expanding on some of them.

Vascular plants have roots that help stabilize the upper parts of the plant and carry soil nutrients and water to the rest of the plant. Thus, roots make possible the forests and grasslands in which we and other terrestrial critters walk or crawl around.

In some species, roots are a means of vegetative propagation, spreading away from a parent plant and sending up new shoots that look like separate individuals but that are all part of one. Aspen is a classical example among the trees, making groves of tree trunks that are all one individual, genetically. Perennial grasses, such as beach rye, can spread rapidly in this way by means of underground stems called rhizomes.

Tree roots sometimes graft to each other, linking their vascular systems and sharing nutrients (and, potentially, pathogens). Grafting is relatively common among neighboring individuals of the same species but is also known to occur between individuals of different species (e.g., pine and spruce).

Neighboring plants of all sorts are also often connected by mycorrhizae—fungi that carry nutrients from plant to plant and from soil to plant. Their networks can be very extensive, connecting plants of different species. As many as eighty or ninety percent of all plants may use mycorrhizal connections. Mycorrhizae are said to be especially dense in perennial grasslands.

Mycorrhizae even make connections to mosses and other rootless plants. Mycorrhizae contribute significantly to growth, survival, and reproductive success of many plants (some orchids even need them for seed germination). However, these useful fungi are inhibited by agricultural fertilizers containing inorganic nitrogen and water-soluble phosphorus. 

There’s plenty of nitrogen (N) in the atmosphere but it is, nevertheless, often a limiting factor for plant growth and development. Nitrogen is also used in plant defenses against pathogens and herbivores. Plants can’t use atmospheric N directly, but N becomes available via a process called N-fixation; this process is catalyzed by enzymes that transform atmospheric N to ammonia and thence to various amino acids that are usable by the plants. This work is done only by various kinds of bacteria and some other one-celled organisms, which have been around, somewhere, since long before plants evolved. Some of these N-fixers live freely in the soil, others associate with the outsides or the insides of roots, and still others are housed in special nodules on plant roots. Within these nodules, the process of N-fixation uses energy provided by the plant’s photosynthesis.

The legumes (peas, peanuts, etc.) are well-known for their nodules inhabited by bacteria called Rhizobia. These nodules are induced by the bacteria in response to chemical triggers from the plant. These bacteria can only fix nitrogen when with a suitable host. Some of these symbioses between plant and bacteria are highly specific—each partner associating only with the other one; and if a different type of bacteria gets into the nodule, it can usurp energy and cause the plant to die. But some Rhizobia are much less fussy, associating with several plant species. In our area, beach pea and lupines (for example) have Rhizobia nodules.

However, many other kinds of plants form symbiotic relationships with N-fixing bacteria of a different type, mostly known as Frankia. These filamentous ‘actinorhizal’ bacteria produce hormones that mimic certain plant hormones and force the root cells to proliferate rapidly, causing swellings (nodules) to form. Local examples of this symbiosis include alders and sweetgale.

Plants with N-fixing bacteria use that nitrogen for better growth and defense. In addition, plants with enhanced nitrogen levels may provide nitrogen to other plants via grafts or mycorrhizae. Many plants with N-fixing bacteria are also mycorrhizal—a three-way symbiosis! In agricultural settings, nitrogen-enhanced plants are plowed down into the ground to improve the next crop. A little N-fixing water-fern is sometimes cultivated to be used as green manure for other crops. Plants with symbiotic N-fixers are sometimes also planted near human-favored trees (e.g., Douglas fir), so that the products of leaf and rootlet decomposition enter the soil and enhance the growth of the favored neighbor.

Roots have all those helpers (so to speak) that contribute to supporting the plants. They also have enemies. Roots are eaten by some above-ground consumers; geese dig the roots of silverweed, bears dig the roots of lovage, angelica, hemlock parsley and the bulb-like tubers of northern ground cone. Some invertebrates (including nematodes, insect larvae) nibble roots or suck their fluids. And there are root-rot fungi that can demolish a root system and cause a tree to collapse.

That’s just the root-y part of the complex soil ecosystem. Fungal hyphae pervade the soil, sometimes reaching high densities. There’s a teeming community of invertebrates: mites, earthworms, millipedes, nematodes, springtails, spiders, isopods, insects….as well as astronomical numbers of bacteria and other one-celled organisms creating complex food webs. It’s an ecosystem that’s not as well-studied as some others but surely has many interesting stories.

Fungi!

more friends than foes

There are tens of thousands of fungal species, which are classified in a kingdom all their own, neither plant nor animal. We become acquainted with some of them in unlikable ways, when they infect us or show up as mildew on our roses. Although we bemoan those fungal invasions, other fungi have been useful to humans in many ways.

Just consider, for a moment, what our lives might be like in the absence of fungi. There wouldn’t be yeast-leavened bread, so no hot-cross buns, chocolate eclairs, or ordinary pb&j sandwiches. No beer or wine, so although South Franklin Street might become more attractive, New Year’s Eve parties might be staid and quiet—and the highways would be much safer. Without penicillin and other antibiotics derived from fungi, we (collectively) would a lot sicker and maybe, in some cases, dead. Some folks would miss the hallucinogenic fungi and many would rue the lack of delectable chanterelles and boletes. Those that create fabric items would miss the many hues of dyes derived from fungi.

Of more fundamental importance, however, are the ecological roles of fungi. Many fungi form connections with the roots of trees, shrubs, and herbaceous plants, providing nutrients from the soil to the plant in trade for carbohydrates from the plant’s photosynthesis. These mycorrhizal fungi contribute significantly to the health and growth of the partnered plants. Our forest would be a poorer place without them!

Thus the fungi give, but they also take away: They are major decomposers of plant and animal matter. If dead trees and leaves didn’t decompose, ultimately the forest floor would be buried and no understory could grow. So, no winter food for deer, no high-bush cranberries or blueberries. Leaves and stems of dead grasses and sedges would make a thick, impenetrable mat over the meadows. Perhaps the only places new trees or grasses could grow would be on recently exposed bare soil (think of receding glaciers, landslides, post-glacial uplift), and then it would be only certain kinds of plants that could cope with conditions there. Furthermore, we’d be surrounded by carcasses of dead animals and small trailside mountains of dog poop that would be only partially diminished by bacterial action.

The activities of fungi sometime appear in unexpected places. For example, recent research has shown that fungi play a role in the formation of hair ice—those wonderful curls of extremely slender filaments of ice (only about one hundredth of a millimeter thick!) that emerge from sodden branches when the temperature is just below freezing, and the air is humid and still. This story has a beginning over a hundred years ago, with Albert Wegener, the astute fellow who recognized the fact that the continents move around. In addition, he noted that hair ice appeared on damp branches of deciduous trees and shrubs that were also laden with fungi; he then surmised that the fungi had something to do with the formation of that hair ice. After a long delay, recent research has confirmed that surmise. Although those old, wet branches harbor several kinds of fungi, one in particular is consistently associated with hair ice. That fungus (Exidiopsis effusa) is a decomposer of wood; it somehow also shapes the ice hairs, preventing the tiny crystals from coalescing into bigger ones. Organic matter in the hair ice, such as decomposed lignins from the wood, might be involved, but that remains to be determined.

Scientists have also discovered a new genus and species of fungus that has medicinal value, known and used in Chinese folk medicine for hundreds of years. This fungus grows on a certain kind of bamboo, as do other species in a related genus. These fungi contain compounds called hypocrellins, which are effective against viruses, bacteria, and fungi, when they are activated by light. And now we know that this new species does too. It just took science a while to catch up with traditional knowledge…

Mushrooms at Crow Point

fairy rings and soldier parades

A walk on the Boy Scout beach/Crow Point trail is almost always rewarding. There’s a variety of habitats, each of which changes with the seasons in its own way.

In late September, there were no geese to be seen in the big tidal meadow or in the river’s estuary. A northern harrier in brown plumage (female or juvenile) coursed low over the river and meadows, spooking at least one crow. A bit above the highest part of the beach, the last flowers of wild strawberry shone on a background of dark green. Several flocks of pine siskins flitted over the seed heads of meadow plants or zoomed between stands of conifers.

On the way from the parking lot to the beach, in the first riverside meadow, the trail had previously been re-routed to accommodate bank erosion. But this time, another large chunk of the bank had fallen into the river, leading to another trail diversion.

Rather than walk the long beach, I chose to weave my way in and out of the spruce groves that line the berm along the shore. These groves sometimes produce interesting finds, such as a bear skeleton or a flourishing stand of orchids.

This time, it was a mushroom show. I know next to nothing about mushrooms, unfortunately. But I was attracted to three in particular. A medium-sized brown one typically grew in long, curved chains. Troops of very small white ones clustered between spruce roots. (I called these ‘armies’, and a friend saw them as pilgrims on a mission, but ‘troops’ is an accepted informal term, I’ve read). My favorites were tiny yellow ones with orange centers on the cap. These usually grew in troops on the berm, especially in some of the groves.

Tricholoma-fairy-ring-Pam
Trichloma fairy ring. Photo by Pam Bergeson

To give me some guidance, I enlisted the help of a friend who does know a lot about mushrooms, and we went out there again a few days later. We made only slow progress as we walked along, because there were so many different mushrooms to look at and discuss. There were lots of Amanita muscaria (common name: fly agaric), both red and yellow varieties. They had the customary whitish ‘warts’ on the cap—except when they’d been washed off by heavy rain. (I call the white bits scattered on the cap ‘streusel’, like the crumbly mixture often scattered on muffins or coffee cake). We found huge boletes, now aged and no longer desirable for eating by humans but other critters had been feasting. There were more kinds of brown-capped mushrooms than my old brain could begin to assimilate.

I learned that the curved chains of brown-capped mushrooms belonged to the genus Tricholoma (I decided, early on, that getting the name of the genus was enough for now; species names could wait). Tricholoma fungi form mycorrhizal associations with tree roots, providing soil nutrients to the trees and obtaining carbohydrates made by the trees’ green leaves. The long sweeping arcs sometimes exceeded fifteen feet in length. Shorter arcs made nearly complete rings. So-called ‘fairy rings’ of mushrooms are well-known in both mythology and mycology (the study of fungi), but I have not found a coherent explanation of why they form these arcs in some cases but not in others.

The numerous troops of small whitish mushrooms turned out to be of several species, mostly in the genus Mycena, but a few in the genus Collybia. They are not mycorrhizal but rather decompose fallen plant parts such as old leaves and flowers.

Those tiny, bright yellow mushrooms belong to the genus Mycena, sometimes called fairy bonnets. I would love to know why troops of these were very common in some groves but not in others.

As usual, I am left with many questions. For instance, how does a fungus decide when to produce sporing bodies? The main part of a mushroom-producing fungus is an underground network (mycelium) of thread-like hyphae; the network may be very extensive. When the time is right, the fungus puts up sporing bodies that we call mushrooms. The mushroom cap releases ripe spores that disperse, potentially starting new individual fungi. (Although they are not the same as the seeds of plants, they have the same function). But what makes one time ‘right’ and others not? This year was said to be one of great bolete production—but what were the conditions that made it so?

And why are some mushrooms purple—what is the function of that pigment? Ditto for red, or yellow, or browns. Some mushrooms have massive thick stalks, almost as wide as the cap, while other perch their caps on feeble, spindly stalks. How come? There is so much to be learned!

Thanks to Jenifer Shapland for a primer on local mushrooms.

Purple mountain saxifrage

a hardy flower and a spring delight

One of the earliest flowers to appear in spring is purple mountain saxifrage. In April some of us make a point of regularly checking certain places where we know it lives, just for the pleasure of watching for the first open flower and then the appearance of more and more blossoms, until there are multiple patches of the pinkish-purple flowers on some of the local rocky outcrops.

purple-mountain-saxifrage-on-April-10-2013-at-Nugget-Falls
Photo by Bob Armstrong

This low-growing plant occurs in Arctic regions around the world, and in alpine areas of central Asia, Europe, and North America. It’s a tough little plant, quite resistant to drought and water-stress. It forms associations with mycorrhizal fungi that provide nutrients and water, in exchange for carbohydrates produced by the saxifrage leaves. As with several other early-season bloomers, the flower buds are actually formed the year before the flower opens, but eggs (in the ovary) and sperm (in pollen) don’t develop until spring.

Female parts of the flower mature before the male parts do, which reduces the chance of self-pollination (pollen fertilizing future seeds in the same flower). Most seeds are produced by out-crossing (pollen fertilizing future seeds on a different plant).

The flowers are pollinated by insects of various sorts, including bees and flies. Early in May, we watched a female margined-white butterfly visiting one flower after another, so presumably there are minute amounts of nectar therein. These insects don’t see the longer (reddish) wavelengths, so they see the flowers as bluish. However, studies have shown that seed production is often limited by low levels of pollinator activity, perhaps in part because bad spring weather sometimes reduces insect activity. In addition, one study showed that as soon as other flowers started to bloom, insect visitation to the saxifrage decreased, as the insects found preferred sources of food.

This is an ecologically variable species, with different types adapted to different conditions of soil, snow-melt, length of growing season, and so on. For example, one study showed that the plants growing in cold, wet soils with late snow-melt had higher metabolic rates and faster production of shoots than those in warmer, drier sites, but they did less well at storing carbohydrates or water for hard times. In some areas, there are two growth forms that grow side by side but differ in structure (prostrate vs cushion-like) and in reproduction: one does better at seed production but the other excels at propagating by shoot fragmentation.

On the Old World Arctic tundra, purple mountain saxifrage flowers and old seed heads are eaten by barnacle geese when they arrive on the nesting grounds, and reindeer eat it too. I have not found information on animals that consume this plant in North America.

A word of caution: If you see this pretty plant in the wild, please do not remove it! That deprives lots of other folks of the pleasure of finding and seeing it in its natural setting.

Plants supplement their income

…with a dabble in heterotrophism

Green plants are called ‘autotrophs’, meaning that they feed themselves . (This is in contrast to all animals, which are ‘heterotrophs’ that gain nutrition by consuming other organisms.) These green plants feed themselves by photosynthesis, converting carbon dioxide and water into sugars (and oxygen). They also draw water and minerals from soils, and sometimes from water. So we are inclined to think of them as functionally independent entities, in terms of nutrition.

There are some salient exceptions to this simple plant-autotroph versus animal-heterotroph dichotomy. The carnivorous plants consume insects as a dietary supplement, so they are, in effect, both autotrophic and heterotrophic (see also http://Juneauempire.com/outdoors/2012-06-22/trails-carnivorous-plants). A few plants are not green at all and live a totally parasitic existence, drawing nutrition from host plants; they could be called heterotrophic too. For example, dwarf mistletoe that infects hemlocks and other conifers in our forests is not capable of much photosynthesis, and depends on its host tree for nutrition. Heavy infestations can kill the host tree. (However, the witches’ brooms that they create are useful to squirrels and birds). Northern ground cone, which is common near the Visitor Center at the glacier, is parasitic on the roots of alders (and a favorite food of local bears).

However, most of the other, supposedly autotrophic, plants actually live in association with other organisms that supply nutrients. Many species, including orchids and blueberries, associate with fungi that supply important minerals to the plant; these associations are called mycorrhizal (fungus-root) (see also http://Juneauempire.com/stories/010707/out_20070107004.shtml). Some species, such as alders and lupines, form root nodules that are inhabited by nitrogen-fixing bacteria that turn atmospheric nitrogen into a form usable by plants. Many trees form natural root grafts with their neighbors, drawing water and nutrition from each other (and sometimes diseases too).

Then there are the so-called hemi-parasitic plants, which I mentioned a couple of weeks ago in this space. They are green and can photosynthesize carbohydrates and live independently, but which also commonly parasitize other plants. They often grow better and set more seeds when they tap a host’s resources, but a host is not absolutely necessary. Their effect on host plants is generally negative, reducing growth and seed production. As far as I can determine (so far), we have three kinds of hemi-parasitic flowering plants in our flora.

Indian paintbrush (genus Castilleja; about twelve species in Alaska): They grow from sea level to the alpine zone. The colorful bracts of the inflorescences range in color from red to pink to yellow. Some are pollinated by hummingbirds, some by butterflies (especially Down South) and some are pollinated by bumblebees. Paintbrushes can accumulate selenium from soils and become toxic to humans and other vertebrates. They parasitize the roots of grasses, herbs, and some trees.

Rattlebox-by-bob-armstrong

Yellow rattle (genus Rhinanthus; one species here): It is also known as rattlebox or rattlepod. The yellow flowers are bee-pollinated. When the petals drops off, after pollination, the remaining green calyx contains the loose (rattling) seeds. A root parasite mostly of grasses and legumes, it is known to decrease the productivity and survival of grasses. Therefore it is used in some regions to restore meadows and prairies where cultivated grasses have been grown; by decreasing the cover of grasses, there is more room for wild flowers and thus a diverse community of plants. And the helpful yellow rattle plants eventually get shaded out.

Louseworts (genus Pedicularis; about twenty species in Alaska): Louseworts have their unfortunate name because of an old, very silly, belief that they caused grazing cows to have lice. There are hundreds of species of lousewort in the world, with flower colors of all hues. Most are pollinated by bumblebees or other relatively large bees, but at least one is also pollinated by hummingbirds. Only some have nectar in the flowers. Louseworts are root parasites, often of members of the heath family, such as blueberries.

The bottom line of all this is that green, flowering plants are not such independent entities as one might think. Many, if not most, of them interact with other plants, fungi, or bacteria to supplement their nutrition. Our forests and meadows would be impoverished without these interactions.

Orchids

extraordinary diversity and behavior

Humans have been fascinated by orchids for ages. When we think about orchids, most of us visualize the flamboyant, exuberant, gaudy floral displays produced chiefly by tropical species or by the activities of avid orchid breeders. Fair enough, but…

All that flamboyance and showiness evolved because each kind of orchid flower is very complex and adapted to particular pollinators. Most of the pollinators are insects, but a few are pollinated by hummingbirds. Each kind of flower is visited, typically, in a very specific way by its pollinating animals. Although some orchids do not require a pollinator but, rather, simply pollinate themselves, the majority set seed after the visit of a pollinating animal. Different kinds of orchids offer different rewards to pollinators, usually nectar, but sometimes special oils or fragrances. Some reward-less orchids rely on fooling visitors, by just looking like they might have a reward and so attracting naïve insects, or (most famously) by looking like a female insect and fooling the male insects into trying to copulate with the flower.

Orchids have actually gone a bit crazy. There are probably over twenty-five thousand species; taxonomists are not sure just how many there are. But there are way more orchids than all the birds and mammals in the whole world, and more orchids than any other kind of flowering plant except perhaps the aster and daisy family. Although they are most common in the tropics, orchids can be found almost everywhere except Antarctica and the very High Arctic, occupying almost any habitat, including on other plants; one even lives entirely underground.

Southeast Alaska has its share of orchids: as near as I can tell, we have about twenty-six species in nine or ten genera (genera is the plural of genus, a taxonomic unit that clusters similar species together). The numbers are a bit uncertain because taxonomists often have differing opinions on how to demarcate the species and how to cluster them. In this space, I intend to introduce each genus that’s found in Southeast, with a bit of information about its name and its biology. Most of our orchids are not as gaudy as their southern relatives, but they share some nifty adaptations with their gaudier cousins. Because I like to know how things work, I’m including information on how the flowers function, that is, how they control the visits of their pollinators—which, after all, is what orchids are famous for!.

Before I launch a discussion of our orchids, it is useful to explain a few things that apply to all or most orchids. By doing so, repetition can be avoided or at least reduced. And, by the way, in case you were wondering, the name ‘orchid’ comes from the Greek word for testicle, because the bulbous roots of some species reminded someone of male gonads.

All orchids produce huge numbers of minute, dust-like seeds that lack stored nutrients for seedling germination and growth. Therefore all seeds depend on forming associations with particular fungi (mycorrhizae) that bring in nutrients from decaying organic matter or from other plants. Finding the right mycorrhiza is a chancy business, and most seeds just die. If a seed finds the right mycorrhiza and germinates, most orchids plants eventually produce green leaves that can photosynthesize carbohydrates, and thus they can live somewhat independently. But some orchids have no greenery and are forever dependent on their mycorrhizae.

I will spare you (and me!) the fine details of the intricate arrangements of orchid flowers, which can be bewilderingly complex. But I will mention one very peculiar and mysterious thing: while an orchid flower is developing, it often (for some odd reason) rotates a hundred and eighty degrees on its axis, so what was up is now down. That is rather mysterious in itself. In one species of the genus Malaxis (at least in the European populations of a species that we have in our area), however, the rotation is a full three hundred and sixty degrees, so what was up is again up. I find this most peculiar—if the goal is to have ‘up’ be ‘up’, why rotate at all? Darwin noted this, and then, to confound all logic, saw that the ripe seed pod UNtwisted itself by three hundred and sixty degrees. Very peculiar. And all of that begs the question: Do those that twist only a hundred and eighty degrees also untwist when seed ripen?? It is all very strange!

Most orchids disperse pollen in clumps, rather than as loose collections of powdery, separated pollen grains (as in most flowers). The clumps of pollen grains are generally held together by sticky material and elastic threads, and sometimes several clumps are stuck together. The clumps are called pollinia. Although some other flowering plants (such as milkweeds) produce pollinia too, this habit is relatively unusual. When they pick up a pollinium, pollinators then carry many pollen grains at a time. This would seem to be very efficient, but actually the seed production of many orchids is limited by too-few pollinator visits.

OK, now for our Southeast orchids. I’ll start with the smallest and least conspicuous, dealing with each genus in turn, working up to some local beauties.

Listera. The genus is named for a seventeenth century English naturalist (Listera). These diminutive plants are known as twayblades, for the two broad leaves flanking the stem. There are four species in southeast, although two are rare. I have seen good numbers of two species along the rainforest trail near Bartlett Cove, and they should be quite widespread elsewhere in Southeast.

The nectar-bearing flowers are tiny, only a few millimeters across, and they are pollinated by equally miniscule insects such as dance flies, fungus gnats, or minute wasps. Darwin thoroughly studied the pollination mechanism of an English species of Listera, and ours apparently work the same way. When an insect touches a beak-like structure in the flower, a drop of very sticky liquid explodes from that structure, catching the tips of the pollinia and gumming them to the head (often the eyes) of the visiting insect. The sticky fluid hardens almost immediately, so the insect flies away with pollinia stuck on its head. After firing the sticky liquid and the pollinia, the female receptive surface (called a stigma) is exposed and ready to receive a pollinium from the next insect. When an insect bearing a pollinium on its head visits a flower whose stigma is exposed, the pollinium contacts the sticky stigma, so pollen is pulled away from the insect and pollination occurs. For all of this to happen, the beak-like structure actually moves, first to put the pollinia in position to be picked up by the exploding drop, and then to expose the stigma so another insect can deposit pollen.

frog-orchid-armstrong
frog orchid. Photo by Bob Armstrong

Coeloglossum. The genus name means ‘hollow tongue’; I have not learned the source of this name; one idea was that it derived from the spur that holds nectar, but since this is shaped like a tiny sac and is not at all tongue-like, this name is puzzling. The common name is frog orchid, but it doesn’t look like a frog (to me), so that name is also a puzzle. This is reportedly a short-lived species, able to flower during its first year above ground and seldom living more than about three years. The flowers can be pollinated by small insects of various sorts, but details of how the flower works are not available; self-pollination is possible.

I’ve seen frog orchids on Gold Ridge, where they are not common. Although they can apparently produce many greenish flowers on each stem, the ones I’ve seen have all had only a few flowers on each short stem. These plants on Gold Ridge are at risk by being trampled by the many visitors that walk above the tram.

Malaxis. Once known as Hammarbya, the newer name of Malaxis comes from a Greek word meaning soft or softening, referring to the soft leaves of some species. The common name is, sadly, adder’s mouth orchid or adder’s tongue. Someone must have thought the flower resembled the front end of a poisonous snake (it takes a very unusual imagination!). There are two species in Southeast, mostly in bogs.

The tiny (less than two millimeters) flowers are yellowish green. They have nectar and a sweet odor, which attract very small insects, such a fungus gnats. Darwin studied one of our species, which also occurs in Eurasia. He observed that a sticky drop holds the ends of the pollinia, and when an insect enters the narrow opening of the flower, it runs into that sticky drop and pulls out the pollinia (on lower, front part of its thorax) when it flies on. When the insect then enters the next narrow flower, the pollinia are pulled off, in contact with the stigma. Apparently this species does not self-pollinate but requires an insect to bring pollen from another plant of the same species, achieving cross-pollination; however, the second species in our area may often self-pollinate.

Malaxis orchids reportedly have the peculiar but useful habit of vegetative propagation by means of little bud-like structures on the leaf tips; these little structures can sprout and grow into new plants.

dance-fly-in-early-coral-root-orchid-blossom
Dance fly in a coralroot orchid blossom. Photo by Bob Armstrong

Corallorhiza. There are two species of these coral-root orchids in Southeast. Both names describe the appearance of the roots, which are thought to look like branching corals. Both species produce fairly tall flowering stems with multiple flowers, either pink or yellow. Both lack any green pigment, so they cannot produce their own carbohydrates and are therefore dependent on their mycorrhizal associates for nutrients.

Both species are visited by small insects, including flies and wasps and bees, that can carry some pollen from plant to plant. However, most seeds are apparently produced by self-pollination, without a visit from an insect bringing pollen from another plant.

The pink-flowered species is often seen in conifer forest, but the yellow-flowered one seems to prefer more open, often deciduous woods.

Goodyera. The genus bears the name of a seventeenth –century botanist. The common name is entirely ridiculous; it is called rattlesnake plantain, although it has nothing to do with snakes of any kind nor is it a plantain. Because the leaves are sometimes mottled with white, some early pioneers may have been reminded of snakeskin and thought, by simple association, it could be used to treat snakebite. However, there aren’t many rattlers where our species lives, so the name seems doubly foolish.

One species of Goodyera grows in our forests. The flowers are white, borne on a tall spike. Each flower is first male, with mature pollen, and then female, with a sticky, receptive stigma (this sequence is called protandry, or first-male). Internal parts of the flower rearrange themselves slightly to better expose the stigma after pollen is removed. Pollination is reported to be accomplished by bumblebees, which first visit the older, female-phase flowers low on the spike, depositing any pollinia they may carry. Then the bees move up the spike, reaching the male-phase flowers and picking up pollinia, on their heads or tongues, to carry on to the next plant. Thus, seeds are typically produced by cross-pollination between different plants.

orchid-Pam
Platanthera. Photo by Pam Bergeson

Platanthera. There are at least eight species in Southeast. Some produce white, very aromatic flowers, while others make greenish flowers, but all bear the flowers on an elongated stalk. These orchids formerly were classified as species of Habenaria, from the Latin word for strap or rein (probably because one of the main flower parts is flat), hence the common name of rein orchid; an alternative name is bog orchid (although some also grow in wet forests). The current genus name seems to mean ‘flat flower’, perhaps referring to the same flower part.

Bog orchids are pollinated by a variety of insects, some mostly by moths or both moths and butterflies, others probably by bees, some by small flies and mosquitoes, and some by almost any insect of the right size and inclination. Our white, aromatic bog orchid is pollinated primarily by moths, at night, and our green bog orchid may have several possible pollinators. Certain species exhibit regional variation in the length of the nectar spur, odor of the flower, and the type of insect pollinators, even within the same species.

Platantheras present nectar in a nectar spur, which is visited by a foraging and pollinating insect, when it enters the flower in the proper way, from the front, and encounters the sexual parts. But at least some species also produce small dollops of nectar on other parts of the flower, perhaps to increase the allure of the flower to insects that subsequently enter the flower in the proper way.

The pollination mechanism is simple: the insect shoves it head into the flower, reaching into the nectar spur, and bumps into the sticky parts of the pollinia, which then attach to the eyes or tongue of the insect. Although cross-pollination is usually the norm, many of them may simply self-pollinate, if no pollinator visits them.

Piperia. Named for an American botanist, two species occur here; they are widespread but rare. They are similar to and sometimes classified with Platanthera, but sometimes they are classified in their own genus. They typically live in open woods. The flowering stem bears a number of small, green or white flowers that are reported to be aromatic especially at night, when they are pollinated by moths. A visiting moth can poke its head and tongue a short distance into the flower, and pick up pollinia on the tongue; an older flower is more open, and a visiting moth bearing pollinia can insert its head far enough to deposit pollinia on the stigma. Piperias are thought to be chiefly cross-pollinated.

Spiranthes. As the name suggests, the flowers spiral up in a tall spike. The common name is ladies’ tresses, because someone thought the inflorescence looks a bit like a woman’s braids. The white flowers are pollinated principally by long-tongued bumblebees. As in Goodyera, the flowers are typically protandrous (first male, then female), and when nectar-foraging bees work their way up the spike, from older flowers to younger ones, the last flowers they visit stick pollinia onto the bees’ tongues. As observed in detail by Darwin on a similar species, the pollinia are attached to a sticky disc, whose stickiness is activated by the bee’s tongue as it passes through the narrow opening to the pool of nectar. When the bee’s tongue is withdrawn, the pollinia are pulled out. On older flowers, the internal parts of the flower have been rearranged slightly, widening the opening where the bee inserts its head and exposing the receptive stigma. Flowers are usually out-crossed, but when there are few pollinator visits, male and female phases of each flower may overlap more, and some self-pollination may occur if a bee does visit. There is one species in Southeast. A study of our species on Vancouver Island, B. C. found that flowers received abundant bee visits and set seed accordingly, but visitation rates and seed production have not been studied here, where bee populations may be less dense.

June-22-Cypripedium-passerinum--Sparrow-Egg-orchid-2-resize
Sparrow’s-egg orchid. Photo by Kerry Howard

Cypripedium. The genus name of ladyslippers or moccasin flowers comes from classical mythology. It refers to the foot of Aphrodite (or Venus), who was formerly called Kypris. Presumably an inventive observer imagined that the foot of a goddess of love might wear a floral slipper. We have at least one species (with white flowers), mostly in open woods in scattered locations, and two others may creep in to the northernmost part of Southeast.

Ladyslippers have no nectar, but they are often aromatic. The flower acts like a trap. When a small bee enters the pouch-like slipper, it cannot get out the same way because of the slippery sides and in-rolled margin of the pouch. So the bee has to exit through the upper part of the flower and, in so doing, it passes by the sexual parts of the flower. In general, Cypripedium pollen is very sticky and readily adheres to the crawling bee, which picks up pollen as it leaves the flower. When the bee enters and exits another ladyslipper, it encounters the female parts first, brushing off pollen on the stigma.

Some species of ladyslippers can become dormant for as long as three to five years, not showing above-ground shoots at all during that time. Prolonged dormancy can be induced by stress, perhaps from a bad growing season or the cost of making many seeds. These dormancy periods sometimes presage mortality, but in other cases, the shoots come up again and the flower blooms after its rest period.

fairyslipper-orchids-by-bob-armstrong
Calypso. Photo by Bob Armstrong

Calypso. The common name of fairyslipper was no doubt inspired by its delicate and lovely shape, suitable perhaps for an ethereal, light-footed creature. The genus name comes ultimately from the Greek word for concealed and more immediately from the mythological goddess, Calypso. She was a beautiful nymph that lived in the forest. According to Homer’s Odyssey, she found Ulysses (Odysseus) when he was shipwrecked on her island, and she kept him for seven years.

The showy, pink-purple flower, usually one per stem, is said to be very aromatic, but it has no nectar. Bumblebee queens are the principal pollinators. Naïve queens (with no previous experience with this flower) visit calypsos but each queen soon learns that there are no nectar rewards to be found there, although the aroma might suggest otherwise. Such pollination by deception is characteristic of many orchids. Supposedly the queen bees learn quickly, so many calypsos are visited only once, and pollen may be removed but not deposited on another flower. Some researchers suggest that the slight variations in color and aroma that calypsos exhibit might facilitate fooling the bees into visiting more than one flower and accomplishing pollination.

The bees enter the open flower but discover no nectar and then back out. When they back up, apparently they hunch their backs and if, on the back of the thorax, they carried a pollinium from a previously visited flower, it gets brushed off on the stigma. A little farther toward the front of the flower, the backing-up bees encounter the pollinia of that flower, which in turn sticks to the back of the thorax, to be carried to another flower—unless the bee has learned its nectarless lesson. Calypso flowers may last more than eight days if not pollinated, but they wither in three or four days if pollination was successful. Apparently, fruit productions in calypso is generally poor, reflecting a low level of successful pollination.

We have one species of calypso here. I have seen it rarely, mostly in open, relatively dry areas. It is a temptation to pick Calypso flowers when one finds them, just because they are so lovely. But that seemingly simple act is likely to kill the plant, because the little, plucking tug can break the extremely delicate roots. So please don’t pick them!

There you have our orchids, and a lovely array it is. It is best not to try to transplant them, because many are delicate, and some are rare, so they should be left where they find themselves naturally. We can enjoy them in their natural places.

Thanks to Mary Stensvold and Ellen Anderson, USFS botanists, who provided helpful consultation.

Flowery fun in Gustavus

an orchid show, and other floral delights

Lady’s slipper orchids are sometimes called moccasin flowers, referring to the shoe-like shape of the flower. One of the petals is modified to form an oval pouch with an opening on top. The edges of the pouch are rolled inward. A small shield-like structure hangs down into the back of the pouch and behind the shield are the sex organs. The flower offers no nectar to visitors, but at least some species have an attractive aroma.

Bees that visit these flowers enter the pouch, but the rolled-in edges keep them from crawling out. So, once in the pouch, the bees are obliged to crawl up behind the shield, in order to get out again. In doing so, they pass very close to the pollen-receiving stigma, leaving pollen from previously visited flowers, and the pollen-bearing stamens, picking up pollen on their bodies to carry to another flower. A very elaborate system for creating the next generation of lady’s slippers.

After pollination, thousands of dust-like seeds are produced. They are so small that they contain no nutrition for a developing embryo (this is true of orchids in general). Lacking a source of nutrition, the seeds have to rely on forming an association with certain fungi (mycorrhizae), in order to germinate and grow. Lady’s slippers are slow growing and take several years to reach the flowering stage.

There are dozens of species of lady’s slippers in North American and Eurasia. They belong to the genus Cypripedium. This name is derived from some ancient Greek words. Cypris is an old name for Aphrodite (a.k.a. Venus in Latin), the goddess of love and beauty. The ‘ped’ part of the name refers to foot or footwear, sometimes rendered as ‘sandal’. So Cypris/Aphrodite/Venus has a rather large collection of sandals in her wardrobe!

Lady’s slippers were familiar to me, from years spent in the Midwest, but I have never seen them in Juneau. So one of my hopes for a recent Gustavus trip was seeing these in bloom. We’d seen their leaves occasionally in the past, but the plants were not then in flower. On this June trip, with the help of a knowledgeable naturalist there, we located clusters of three species of Cypripedium. There was a large-flowered white one (C. montanum, or mountain lady’s slipper). A small-flowered, round white one with some brownish spots is called C. passerinum (sparrrow’s egg or northern lady’s slipper). A yellow-flowered species has often been classified as a subspecies of C. calceolus, but more recently botanists seem to consider it to be a separate species, C. parviflorum, the small yellow lady’s slipper.

June 22 Cypripedium passerinum Sparrow Egg orchid 2 resize
Cypripedium passerinum, sparrow’s egg lady’s slipper. Photo by Kerry Howard

Lady’s slippers and many other showy orchids are often collected from the wild by willful gardeners. But this practice has led to the near-extinction of some species. The slow-growing habit, low levels of pollination and seed set, and the need for mycorrhizal fungi make recovery of exploited populations slow and difficult. So these plants should never be harvested from their native habitats.

June 22 Cypripedium Yellow Orchid 2 resize
Cypripedium parviflorum, small yellow lady’s slipper. Photo by Kerry Howard

We found other orchids too. Tiny twayblades are much more common in Gustavus than in Juneau. They are pollinated by minute flies and wasps, as Darwin documented long ago. Coralroots and so-called rattlesnake plantain are common in Juneau as well as Gustavus.

Orchids were not the only flower show in town, however. Lupines created hills of blue on the beach dunes. Cow parsnips and buttercups brightened beachside meadows. Roses and irises added splashes of color. One meadow was thoroughly decorated with the small white inflorescences of Tofieldia, which is easier to say than the ponderous common name of sticky false asphodel. Sticky it is—the stem sometimes captures tiny insects. Apparently, some botanists thought the inflorescence resembled the European asphodel, which in Greek mythology grew in the meadows where the souls of the dead walked. Great stretches of forest understory were carpeted by the leaves of deerheart, which sent up its small white spires of flowers, and the nearly-luminous, wide, white flowers of bunchberry (one of my companions is alleged to have said that they lighted the way to the outhouse in the darker hours!).

Indian paintbrush provided the most stunning floral array. Here in Juneau we see some yellow-flowered ones and (especially at higher elevations, I think) a few red-flowered ones. But in Bartlett Cove we found a beach meadow simply covered with paintbrush flowers: yellow, red, orange, particolored, and every combination in between. Quite splendid.

Orchid variations

the complex lives of some fascinating flowers

Southeast Alaska has several species of orchid, which are not as gaudily showy as the types cultivated by orchid fanciers, but they have their own allure. Many local folks are familiar with the white bog orchid, whose tall inflorescences send out such a lovely aroma. This species is probably pollinated by moths that come to collect nectar. The calypso or fairy slipper orchid draws in bumblebee pollinators by looking lovely and smelling sweet, as if it offers nectar, but it has none. Visiting bees learn quickly that these flowers offer no food reward, so successful pollination depends on a supply of inexperienced bees. (Calypsos, and perhaps other orchids, should not be picked, because that tweaks the delicate root system and is likely to kill the plant.)

fairyslipper-orchids-by-bob-armstrong
Calypso orchid. Photo by Bob Armstrong

In addition to a wide variety of relationships with pollinators, orchids and many other flowering plants have an intimate relationship with fungi that connect with their roots. This mycorrhizal (fungus-root) relationship is classically thought to be mutualistic: both partners get something from it. The fungus gets carbohydrates from the plant, which typically has chlorophyll (green pigment) and synthesizes sugars that the fungus cannot make for itself. The flowering plant gets nutrients that the fungus gleans from the soil or decaying organic material. Some researchers suggest that mycorrhizal associations were probably essential when plants began to colonize land, millions of years ago.

Orchids, however, take mycorrhizal relationships to new levels of complexity. All orchids produce minute, dust-like seeds. The seeds are so tiny that they contain almost no stored carbohydrates or other nutrients that are needed for germination and growth. They rely on mycorrhizal associations to provide the nutrition needed for germination and initial growth. Thus, all orchids begin their lives as parasites, not mutualists, of fungi (the fungus gets nothing from the seed).

Now the fun begins! Some orchids have no green pigment, so they can’t photosynthesize carbohydrates to give to the fungus. These species remain parasitic on their fungi throughout their lives. The fungus may extract nutrients from the soil and decaying vegetation. However, in many cases, the root-associated fungus acts as a conduit for carbohydrates and other nutrients from a tree (which does have green pigment and can synthesize carbohydrates). So the orchid then is also indirectly parasitic on the tree to which it is connected. For example, in the yellow coralroot orchid (Corallorhiza trifida), which grows here, the fungal associate connects the roots of several species of tree to the orchid, and the orchid thus pirates nutrients from the trees. Even orchids with green pigment and photosynthetic ability may extract carbohydrates from the associated fungus (and a connected tree) without giving anything back, so they, too, are at least semi-parasitic, in many circumstances.

In a further evolutionary complexity, many orchids ‘eat’ their fungal associates, digesting the ends of fungal filaments that connect to the orchid. If the orchid does no photosynthesis, it thus seems to be destroying at least part of its essential source of nutrition. Even if the orchid can photosynthesize carbohydrates, digestion of filaments would interrupt the derivation of materials by the orchid from the fungus or a connected tree, at least partially.

The digestion of fungal filaments opens up many questions, to which I’ve found no concrete answers in the literature (although this fact has been known for over a hundred years): Why would the orchid destroy a major source of nutrients? Is it not needed any more? Or are only certain filaments eaten? What is the contribution of the digested filament itself to orchid nutrition, compared to what the filament delivers from a tree? What is the effect of filament digestion on the fungal organism? Does destruction of the orchid-connected filament tips affect the growth and reproduction of the fungus, as well as limiting its expansion in the orchid roots?

Whether parasite or mutualist, some orchids keep their mycorrhizal associations all their lives, some change their fungal associates as they grow, and some apparently become independent of fungi as they mature (especially if they grow in rich soil with good sunlight).

Things get still more complex: Within some orchid species, genetically different individuals have their own, specific mycorrhizal associates. For example, different genetic types of the spotted coralroot (Corallorhiza maculata), another local species, are reported to have different mycorrhizal associates, accompanied by subtle differences in floral shape. A given population of this coralroot orchid may contain several genetic types (or races) of the orchid, each with its own floral features and fungal associate, potentially deriving nutrients from a variety of trees.

Worldwide, the orchid family encompasses many thousands of species, hugely diverse in floral structure, as well as habitat, leaf shape, life history, and so on. The traditional explanation for the great diversity is adaptation to an equivalent diversity of pollinators. For instance, both of our local species of coralroot orchids are pollinated by small insects such as dance flies, in contrast to the bee-pollinated calypsos and the moth-pollinated bog orchids. However, it has recently been suggested that some of the great diversification of orchids may be related to adaptations to different fungal partners. The variety of floral design and fungal association within the single species of spotted coralroot suggests that this may be a step toward the origin of several new species.