Clarion Call--Part 2

The first English colonists to land in Virginia in the early 1600s were enchanted by the flashy trumpet vine blooms. They sent seeds back to England—presumably earning the enduring enmity of the fussier British gardeners. The vine is native to southeast United States, but like kudzu, it happily and obnoxiously thrives in many foreign sites. When I surfed the web for information on the vine, nearly as many websites offered suggestions for eradicating it, as described its attraction for hummingbirds. I like it because it masks the view of the ugly outbuildings, but also looks very attractive—to say nothing of the enjoyment I get watching pollinators come for a nectar sip.

Nectar is a sugar-rich liquid that many blossoms secrete, to attract hummers, bees, butterflies, and other pollinators. It is much more than the bland sugar water that we fill our hummingbird feeders with. The plants have evolved a clever technique of adding smelly chemicals to the nectar that emit attracting aromas to flying critters who have a sweet tooth. But nectar has even more goodies: a complex blend of many amino acids that constitute protein. So a hummer not only gets a sugar high, but ingests crucial protein. When a hummer’s sweet diet consists primarily of human offerings of sugar water in a feeder, the bird must supplement this diet by finding tiny spiders and insects for its protein. I doubt that I could come up a balanced diet as good as nectar, even if I were to try to find some way to add a pinch of amino acids to my feeder.

Of course, the flower’s sweet gift is not solely a generous gesture to pollinators. It requires some energy on the part of the plant to manufacture nectar—something it really doesn’t need for itself. But it does need to have its pollen transported from bloom to bloom, in order to inseminate its reproductive structures, and it hasn't yet evolved to fly. The (humming) birds and the bees do that for it. When the hummer ducks its head into a blossom, it withdraws it coated with pollen. When a bee waddles down inside, it must brush against the flower’s reproductive organs, coating itself with pollen in the process. It’s a wonderful example of one of nature’s symbiotic relationships—an interaction between two different organisms, to the advantage of both.

The bloom time for the trumpet vine is just a few weeks in late July. There is no other nectar-offering plant close to my outdoor tub. I think I’ll want a bath more often at this time of year, just so I can get more of the aerial pollination show.

Clarion Call--Part 1

By mid-July the trumpet vine is in full bloom, with its brilliant orange-red blossoms, a full three inches long—beckoning all pollinators to come feast. The blossoms on this vine are well named, as they are narrow and long, with the outer end flaring, much like a trumpet. The call goes out, in the form of attracting aromas that entice hummingbirds and bees to come for free sips of nectar, in exchange for the satiated creature passing its pollen to adjacent flowers.

I sit in the tub in the evening, watching the aerial visitors stop by for a drink, just before dusk settles in. A mere 10 feet from the tub is a gorgeous, massive trumpet vine that completely covers and hides a homely storage shed. I watch a hummingbird visit a blossom, hovering like a mini helicopter, while the bird’s extremely long tongue dips deeply, seeking the sweet nectar. He sips twice, three times, then acrobatically zips over to the next bloom. While feasting, he remains on alert, knowing that when his head is plunged into the trumpet, he is temporarily blinded. He frequently pops his head back out, surveys the area for any potential predators, then dives back in for another drink.

I watch him for a few minutes, flitting from bloom to bloom—dipping only once into some, but going back a dozen times to others. Do some blossoms offer more nectar than others? Is the nectar sweeter in some? Has another hummer beaten him to the prize and already sucked up most of the offering in some of the blooms? On occasion, when he’s looking around for any threats, he turns my way and his brilliant ruby-colored throat flashes at me, dazzling me for a brief moment.

A little later a stout bumble bee wanders into the realm of the vine, drawn in by the sweet aroma. Rather than hover, the bee lands on the trumpet flare and waddles down inside—disappearing from my view. A few seconds later she emerges, coated with pollen, and flies to another bloom—thereby inseminating it.

The trumpet vine—also called the trumpet creeper and the cow itch vine—is an aggressive plant that, once having achieved a toehold in your yard, will threaten to become the one-and-only foliage in the area. It grows incredibly fast—adding several feet to its reach each summer. It wants support (being a member of the vine family) and will accept most anything stiffer than it is: a tree, a wall, a fence, or even a cow, if it doesn’t move fast enough. In fact, the moniker “cow itch vine” stems from the leaves of the vine causing a skin irritation. Cows are apparently especially susceptible... especially when they don't move.

One does not want to plant a trumpet vine within reaching distance of a vegetable garden. If you do, within a few short years you’ll have the vine choking out all the veggies. They send out roots, resulting in tiny vines popping up like mushrooms after a rain. If these little babies are not quickly nipped in the bud (I’ll take that pun), the area will soon be awash in trumpet vines. Sometime in late winter I ruthlessly prune back the vine to a size that will keep next year’s new growth contained.

More on trumpets next time…

Fig-Wasp Mutualism

The deeper biologists delve into the workings of nature, the more they come to appreciate and understand the complexity and entanglement that exists between species. No living entity is in isolation. Every plant and creature has a relationship with and depends upon countless other life forms around it. The web of life connects us all, with varying degrees of interdependency.

Remove one species and there will be manifold types of impact on all species connected to it—even those remotely connected. The web of life has evolved to be so interdependent that if one link is severed, the whole thing might not collapse but it will surely change. We humans are causing the ongoing extinction of numerous species every day, with little comprehension of how we are upsetting the exquisite balance of nature.

Mutualism is the strongest kind of tie between two species, wherein both of them benefit from and depend on each other. Pollination is a common type of mutualism. For example, most flowering plants depend on bees, birds, and bats to spread pollen to other plants of the same species—completing the process of sexual reproduction. In return, the plant may offer the pollinator sweet nectar or some of its pollen for food. If the critter is pleased with the meal, it will fly off—carrying some pollen with it—to seek another plant of the same species, and thus fulfilling the sex act.

Modern agriculture relies heavily on bees for pollination of fruits and vegetables. Many bee colonies are being decimated in the last few years, however, and agricultural folks are in a panic. Is the bee-plant balance being degraded?

Some plant-pollinator mutual relationships evolve to become so specialized that only one kind of insect is able to pollinate one kind of plant. They become completely dependent on each other. If one goes extinct, the other must follow. There are numerous species of tree for which there are no further offspring possible, because their pollinator has died off. On the island of Mauritius, for example, there have been no tambalacoque saplings for some 300 years, because the dodo bird—which once spread the tree’s seeds—went extinct in the late 1600s, having been hunted down by people who arrived on the island. Only ancient tambalacoque trees are left. Soon they may also be gone (unless a new pollinator can step in).

One of the more spectacular examples of complete mutualism exists between fig trees and the wasps that pollinate them. There are some 750 species of fig tree around the world (mostly in tropical climates) and 750 species of wasp—one for each kind of fig. The fruit of the fig is hollow, with one end open and with a tiny array of flowers inside the fruit. The wasp climbs inside, lays her eggs on a flower and promptly dies. Later, her eggs hatch, larva eat some of the flower’s seeds, and pupate. Yet later the adult wasps emerge, mate, and the males then promptly die. The impregnated females—now coated with pollen, as they’ve mucked around inside the flower for some time—fly off to find another fig tree of the same species, crawl inside the fruit, and pollinate its flowers.

I don’t believe that such an exclusive example of mutualism exists around me. Most local plant and animal species are generalists. But I can’t help watching a bee or butterfly, loaded with pollen, and wish that it fly on and visit many kinds of flowers and help to bring about more of them. And I can’t help but wonder what delicate examples of mutualism do exist around here, that are in danger of being interrupted. Every critter is precious!