Category Archives: Berries

Red: A ticket outta here (for travelers that have already come a long, long way)

The coming wave of songbird migration has plants getting excited: finally they can get the kids out of the house before winter’s rigors set in. As thrushes, vireos and warblers move southward by the millions, their hunger creates an opportunity for seed dispersal that many plants have grabbed with enthusiasm. Look around in the late summer woods and you’ll see berries fattening up, preparing the bribe for passing birds. Bright red is the color of choice, the hue most likely to seduce an avian eye, so berries tend toward the garish, not the subtle blush.

We’re a few weeks away from the peak of migration (late September through early October brings the largest numbers), but the plants are ready. These eager food vendors include spicebush, dogwood, yellow Mandarin, Jack-in-the-pulpit, and Solomon’s plume.

prosartes lanuginosa fruit

Fruit of Yellow Mandarin (also known as Fairybells, Prosartes lanuginsoum)

Jack-in-the-pulpit fruits (Arisaema triphyllum)

Jack-in-the-pulpit fruits (Arisaema triphyllum)

Fruits of Solomon's plum (Yellow Mandarin (Maianthemum racemosa). Often also called "False Solomon's Seal."

Fruits of Solomon’s plume (Maianthemum racemosa). Often also called “False Solomon’s Seal.”

Yellow Mandarin has an interesting family tree. It has a few siblings in North America, but all its other close relatives are Asian species. This whole clan was for years classified in one genus, Disporum, but the North American species are now recognized as distinct enough to merit placement in their own genus, Prosartes. Solomon’s plume and Jack-in-the-pulpit also have close relatives in Asia. This Asia-America connection is echoed by the biogeography of many other species, especially among the plants of the Southern Appalachians which often have close affinities to species in East Asia. Boufford and Spongberg, scientists from the Harvard Herbaria, summarized the situation:

The similarities of the forests of Japan, central China, and the southern Appalachians in appearance as well as in ecological associations are in many instances so great that a sense of déjà vu is experienced by botanists by one of the regions visiting the other.

The list of Appalachian species with very close East Asian kin is long and, surprisingly, is much longer than the same list for plants with close kin in western North America. Japan is closer than Oregon, it seems. A few of the more familiar examples include: tuliptree, magnolia, dogwood, Virginia creeper, mayapple, ginseng, partridge-berry, blue cohosh, witch hazel, and honey locust. And, of course, the aptly-named “Mandarin.”

Donoghue and Smith’s analysis of this pattern concludes that close evolutionary connections between East Asian and Eastern North American species are “exceptionally common in plants, apparently more so than in animals.” Their work suggests that “many temperate forest plant groups originated and diversified within East Asia, followed by movement out of Asia at different times, but mostly during the last 30 million years.”

These botanical connections are reminders that Asian and American temperate forests were once connected, a connection that was severed as the world dried and cooled in the late Cenozoic. But it is also the result of a few long-distance dispersal events between climatically similar areas.

Animals move to the beat of a different biogeographic drummer. Their kinship patterns are more predictable: western and eastern North America share many close relatives, connections south to the tropics are also common.

So the migration of American birds is powered by Asian food. The botanical restauranteurs hope that the birds opt for the take-out option, carrying seeds away from the parental storefront. Most of these seeds will land a few meters from the parents, but a very small number might make a huge leap, perhaps landing in southern Mexico or on the coast of South America. There, they’ll likely perish. But the biogeographic future is written by the one or two that can put down roots and flourish.

The same is unfortunately true for plant diseases. A few long-distance migrants are reshaping the forests of the world. It is no accident that so many of the more notable plant-killing invasive diseases in the Southern Appalachians have their origins in Asia. Once they get over here they find a “home way from home,” minus the constraints that they experienced in their homeland.

I’ve rambled about the color red before, both here on the blog (“Quite possibly the most overused image of North American birdlife”) and in The Forest Unseen (“November 5th — Light”). I’ll note briefly here that until the leaves fall in a few weeks, the plants face an uphill battle against the physics of light in the forest. It is dark in the woods these days (photography is impossible without steadying the camera on my boot or using a flash). The summer tree leaf canopy is not only robbing most of the light, it is selectively stripping out the reds. Only when a shaft of sun sneaks through a canopy opening do these fruits truly shine. As autumn comes on, the botanical beacons will light up more often.

Thrushes: get ready.

Act I of Autumn

A vigorous belt of chilly rain passed over Sewanee this morning. In its wake, a Canada Warbler feeding on the shrubs in our garden. This is a bird of the boreal forest, found here only during migration. Cool rain, falling temperatures, a forecast for a week of low humidity and clear sunny skies, and the Bird from the North: these all speak of the season’s change.

The plants are ready. Many local species make use of the autumnal surge of birds to complete their pollination and seed dispersal. Cardinal flowers bloom along lake edges, beckoning hummingbirds with their crimson blooms. Dogwood and beautyberry offer brightly colored fruits to the passing thrushes, vireos and warblers. These birds feed on North American insects all summer, then become frugivorous on their tropical wintering grounds. They start the fruity feast right here, gobbling the fruits of our native shrubs and depositing the seeds a few hours later.

One of the most abundant of these fruiting shrubs is spicebush (Lindera benzoin), a species that is particularly common on the mountain slopes. This has been an incredible year for spicebush. I’ve never seen so many fruits. The warm spring must have suited them.

Like Christmas trees loaded with goodies, the plants will be stripped bare when the party gets going. For now, they sit in a quiet forest, waiting for the rambunctious guests to arrive. But unlike the treats on Christmas tree which make up just a small part of the festive food, these berries are the main meal for migrant birds. Now that dogwoods are nearly gone from our forests, killed by an invading fungus, spicebush is a lifeline for the feathered travelers.

Deck the… lab walls

My colleague, Jon Evans, asks students in his Plant Systematics and Evolution class to produce a holiday wreath at the end of the semester. Their challenge: to build an attractive wreath using as many plant species as possible. Sewanee’s 13,000 acres have no shortage of plants to select from, over one thousand species at last count (of course, no rare species find their way into the wreaths).

The wreaths are hung on the walls in Spencer Hall, giving us all a nice boost as we work on final exams.

Luckily, the Microbiology class has chosen not to mount their ripe petri dishes on the adjoining walls.

Mistletoe

A single mistletoe plant is growing near the top of an ash tree behind Shenanigans and Woody’s Bikes. Mistletoe is not common in Sewanee, although it can be quite abundant on the lower slopes of the coves.

American mistletoe, Phoradendron leucarpum (literally, the "white-seeded tree thief")

Recently, biologists have realized that mistletoe is a very important part of the ecology of forests. In fact, mistletoe has such a major effect on other species that it has been called a “keystone species,” one of the major determinants of a forest community’s vitality. How so? Mistletoe steals some of its host tree’s food and combines this with the food that it makes for itself through photosynthesis. This combination of a big trust fund (the tree) and a steady job (the mistletoe’s own leaves) allows the plant to live large, offering abundant nectar in the early spring and fat, nutritious fruit later in the year.

Bees love the nectar which comes earlier in the year than the nectar of most other flower species. Birds and many climbing mammals adore the fruit. The pulp of the fruit is sticky, ensuring that it will stick to branches after it has passed through the bird. More, the seed is often so gummy that it sticks to the birds’ feathers. Birds have to grab the seed, then wipe it off on a branch — a perfect way for the mistletoe seed to get placed exactly where it needs to be. So, this small plant is used by dozens of invertebrate and vertebrate animals. One butterfly, the great purple hairstreak, has gone so far as to become wholly dependent on the plant. Its caterpillars will eat nothing else.

In other parts of the world, including the western U.S., different mistletoe species provide a similar range of services. Some even provide favored nesting areas for many birds. A review of mistletoe biology a few years ago stated that, “…the widespread perception of mistletoes as destructive weeds needs to be challenged. Many landholders, managers, and even biologists regard mistletoes as invasive pests, damaging to individual trees and detrimental to forest health. [But] …mistletoes have a substantial positive role in many forests and woodlands, and should be given appropriate recognition.” (from: Watson, D. M.. 2001. Mistletoe — a keystone resource in forests and woodlands worldwide. Annu. Rev. Ecol. Syst. 32:219–49)

Of course, mistletoe has other roles in the ecology of our world. So, I’ll sit and do my end-of-semester grading under the thief, ever hopeful that songbirds will visit.

A tangle

Our two most vigorous invasive plant species, privet and oriental bittersweet, are wrapped into each other at Lake Cheston. A moment’s reflection from the perspective of a hungry bird hints at how these species manage to spread so successfully. Unfortunately, their fruits have no gastronomic value to humans, except when passed through a goat and turned to milk. Bittersweet, despite its appealing red color, is slightly toxic to humans but not to goats.

Their twining reminds me of the Bramble and the Rose.

Migrant thrush

Despite the best efforts of our resident mockingbird, the beautyberry shrubs are still loaded with fruit. Today, two Swainson’s thrushes (Catharus ustulatus) found the bounty and have been feasting ever since. They can swallow a dozen fruits per minute.

Swainson's thrush -- note the smudged spots on the chest and the buffy eyering

Swainson’s thrushes nest in the spruce-fir boreal forests of Canada and the coniferous woods of the western U.S. The ones in our garden are on their way to South America, where they will spend the winter. Interestingly, many birds in western North America fly due east for thousands of miles before heading south. This seemingly wasteful route (why not fly directly south?) appears to be a consequence of their history: the western birds are descended from easterners and they retrace the migratory route of their ancestors.

Spicebush berries

Berries on spicebush plants are now fully mature. Migrating birds love them, as do bears and other woodland animals. The berries are fairly fatty so they help animals to stock up on energy for either migration or hibernation. The spicebush plants have presumably timed the ripening of their fruits to coincide with the surge of migrant birds that are now moving through our forests.

I sampled a few berries and they taste like a cross between allspice and liquorice, neither of which are high on my list of flavor preferences but then I’m not a wood thrush or a bear. The aftertaste lingers and matures into a sharp cayenne. According to Foster and Duke’s Medicinal Plants and Herbs, Native Americans used tea from the berries for coughs and other ailments and they squeezed oil from the berries to rub into rheumatic joints.

Clicking on a thumbnail will open a larger image.