Bog plants and bird feeder

Just after mid-May, the alders and cottonwoods were suddenly (so it seemed) in full leaf, the fresh, bright green a pleasant contrast with the dark conifers. Even the blueberries and other understory shrubs made a new layer of green above the mosses. Hermit thrushes added their welcome voices to the canopy and fox sparrows tuned up in the thickets.

Early in the fourth week of May, I poked around in some low-elevation bogs (muskegs). Several species were beginning to flower—bog blueberry with deep pink buds and young flowers, bog laurel with broad, pink petals, and bog rosemary with small, pink flowers. The white flowers of trailing raspberry (or five-leaf bramble) starred the mosses under the scattered trees. The distinctive few-flowered sedge was surprisingly colorful, with vibrant green leaves and a yellowish inflorescence. An unidentified sedge with pale green leaves was common but only a few were yet in flower. Labrador tea, lupines, and buckbean were budding. Round-leaf sundews were still just tiny rosettes, their sticky, insect-catching leaves glittering in the sun.

I found a single specimen of a weird little herb (Geocaulon lividum) sometimes called bastard toadflax , but also known as pumpkinberry or timberberry or other common names. Seldom common, it is nevertheless widely distributed across northern North America. It’s a hemiparasite—getting some of its nutrition from its green leaves and some by parasitizing the roots of other plants. It’s not fussy about its host plants; it parasitizes anything and everything from pine trees and blueberry bushes to asters and horsetails to sedges and grasses and even others of its own species.

Photo by David Bergeson

This plant makes only a few small inflorescences; each inflorescence typically has three flowers, usually one female flower in the middle, flanked by two male flowers that drop off eventually. The open flowers are dull yellowish-green with purple marks and I’m guessing they are pollinated by flies or beetles. The orange-red fruits are few, each one with a single seed. Very little seems to be known about seed germination and dispersal. But the seeds are sometimes harvested and cached by Arctic ground squirrels up north and presumably eaten, perhaps sometimes dispersed, by other rodents. It seems likely that birds would take the colorful, fleshy fruit and potentially disperse the seeds.

The fruit has plenty of sugar in it, especially when fully ripe at the end of the season (usually late summer). Estimates of sugar content found that each fruit has about thirty milligrams of sugar, which is more than blueberries or most other fruits in Southeast. Despite the sugar content, the fruit is reported to be just barely edible or tasteless to humans.

Here at home, there’s lots of action on the pond. As many as five male mallards gather, all good pals now that their lady friends are incubating eggs. That changes, though, when one late-nesting (or re-nesting) couple shows up, and the male of that pair harasses the peaceful gang, keeping them well away from his mate.

The bird feeders are busy places. Siskins, juncos, chickadees, and nuthatches visit the seed feeder that hangs over the pond. A jay slams into the side of that feeder, knocking cascades of seeds down for the ducks.

The peanut-butter feeders are the most fun. They’re just little blocks of wood with pits drilled into them, to hold a small gob of peanut butter. Chickadees and nuthatches went crazy over them, but now the juncos almost monopolize them. Juncos are not nearly as agile as the smaller birds, but they cling and stretch (and often fall off) to get a nice bite. Sometimes they perch on the deck railing and fly up to stab and grab out a bill-full.

The jay does the stab-and-grab method too, but he’s a bit rougher, hitting one of the smaller peanut-butter feeders hard enough to knock it off its hanger, so it fell to the deck and broke into four pieces. But that’s not the end of the jay’s mischief. It has started to come to the deck railing to scarf up leftover bits of cat food that I commonly leave out for a raven. One day that jay made off with a whole set of chicken ribs, a load that it could barely carry to a nearby tree. The raven was out of luck again.

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Plants supplement their income

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.

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.

Parasitic flowering plants

When we think of parasites, we usually think of tapeworms, ticks, fungi, and assorted micro-organisms. But the world of flowering plants provides some interesting examples of a botanical version of parasitism, in which one plant extracts nutrients from another. We have two quite conspicuous and common kinds of flowering-plant parasites: hemlock dwarf mistletoe (Arceuthobium campylopodium) and northern ground cone (with the resounding name of Boschniakia rossica). Both of these species are entirely parasitic (or almost so). They derive all or almost all of their nutrients from their host plants and are unable to survive without a host.

You may have noticed the ‘witches brooms’ of gnarly, tangled branches that are the result of a mistletoe infection. The mistletoe alters the balance of growth hormones in hemlocks (and sometimes other species), causing the ‘brooms’. Male and female mistletoe plants are separate, with very small, inconspicuous flowers. Pollination is mostly by wind. When the seeds mature, they are discharged explosively; they are capable of travelling ten yards or more. Because they are sticky, they adhere to other branches or trunks and start new infections. This species has been reasonably well studied, because heavy infestations decrease the economic value of the timber.

 

The ground cone pokes up above ground in June. All we see is the cone-like inflorescence of tightly packed, brownish flowers; the rest of the plant is underground. Ground cone is commonly parasitic on the roots of alders, and sometimes other species, including blueberries. Various insects may visit the flowers and accomplish pollination; occasionally we have seen bumblebees probing the flowers. The seeds are minute and very numerous. The biology of this species apparently has not been studied in detail, as I can find no scientific papers on the subject, but the medicinal uses of this plant are reported to be many. We do know, from local observations, that bears frequently dig up and eat the underground base of the flowering stalk.

In addition, all orchids depend on their mycorrhizae (fungal associates) at least at some time in their life history. Some researchers consider the relationship to be mutualistic, with both participants gaining some advantages, and that eventually may be the case when the adult orchid develops green leaves and can provide carbohydrates to the fungus in return for soil nutrients. However, other researchers refer to mycorrhizal associations as a parasitism by the orchids on the fungi. This seems especially applicable in the case of orchids that develop little or no green tissue as they mature, so they can contribute nothing to their fungal associates. We have two species of the genus Corallorhiza (coralroot), one of which has no green tissue at all, while the other has a little and so can make some carbohydrates. They are both parasitic on fungi for all of their lifespans, but the relationships are even more complex: they can indirectly parasitize green plants through their fungi, which attach to the roots of trees and shrubs (which have their own mycorrhizae), and draw nutrients from those hosts.

Less well known are the so-called hemi-parasites, half parasitic and half independent. They have chlorophyll and can synthesize carbohydrates, but also commonly latch on to other plants and capture some nutrients from these hosts. We have a number of hemi-parasites among our local flowers.

The plant called yellow rattle or rattle box (Rhinanthus minor) grows in open areas at low elevations. This species is capable of parasitizing the roots of many other herbaceous species, including grasses. A single Rhinanthus plant can attach itself to the roots of several other plants. Some plants, however, are able to resist invasion by the roots of the parasite. Rhinanthus plants clearly benefit from the parasitic connections, growing and reproducing better if they are connected to a host. Some hosts, such as legumes, are better than others in providing the parasite with nutrients. In addition, the parasite can take up defensive chemicals, such as alkaloids, from the host, and thus reduce the risk of herbivory. The effects on the host plants are negative, because many of their nutrients are drained away by the parasite; parasitized hosts have decreased growth and reproduction; the negative impact is greater in some hosts than in others. There are indirect effects of Rhinanthus parasitism too: parasitized hosts have lower ability to compete with other plants in the community, and lower ability to recover from herbivory, which then affects the relative abundance of various species in the entire community.

Photo by Bob Armstrong

There are three species of Indian paintbrush (Castilleja) in Southeast, but only one has been studied much, and those studies were conducted elsewhere. In general, members of this genus grow better, flower more, and resist herbivory better, when they are connected to a host plant. Legumes seem to be better hosts than other plants, and two or more hosts may be better than one. When a parasitic paintbrush plant dies and decays, decomposition is accelerated, and co-occurring species have increased productivity, which may counter the usual negative effects of the parasite to some degree.

The genus Pedicularis—the louseworts–has about five representatives in our area, which have not been studied directly, as far as I can tell. In general, the negative effects of parasitism by different species of lousewort may vary among host species, and different louseworts have different host preferences. Some louseworts are reported to have mycorrhizal associations too, collecting nutrients via the fungal connection in addition to the usual direct parasitism.

Clearly, the world of the parasitic flowering plants is complicated, and it gets more complex as more studies are conducted. All those pretty (and not so pretty) flowers are intricately involved with many ecological interactions, and what we see above-ground is only a small part of the story.