Sunday, February 26, 2012

A Quiet Pestilence

If you love wild spaces and wilderness and scenic vistas of true Colorado wildflowers, as well as the diverse wildlife dependent on them, be assured that these will all soon be gone if we continue to allow weeds to spread. And we have allowed it; too often, we have participated in it! Whether our involvement with weeds is deliberate or inadvertent, we have a happy effect on them. Exotic weeds, when they are present, send a strong message that our ecosystems are not healthy. When they take over completely, they tell us that the situation is terminal. For example, the Office of Technology Assessment reported that by the year 2000, most plants in our national parks will be exotics.

The battle against exotic weeds needs to be joined before the problem becomes obvious, because by the time most of us become aware of weeds, it will be too late. If that sounds too extreme, know that we are losing this battle in increments of time and space—4,600 acres each day; 2,600 square miles of public lands (more than two Jefferson Counties worth) lost here in the West for each year we delay. At that rate, how long before there is nothing of wild America left? Yet the biggest difficulty is impressing people that this is important.

As we seem to have more experience with fire each year here on the Front Range, we also encounter more weeds, and the situations are similar. Like wildfire, exotics can completely destroy the vegetation in an area. Unlike wildfire, from which the land quickly recovers, weed damage is often permanent. Weeds strike an ecosystem like fire in dry tinder. The earth may not look scorched, may even be covered with green leafy plants with attractive flowers, but it is in many ways sterile nonetheless. Nature sometimes helps us put out wildfires but never seems to help put out exotic plant infestations. Sometimes fire improves an ecosystem; weeds never do. Unlike wildfire, however, we haven’t learned to fear weeds enough.

Because of their origin and their spread, some weeds, like the common yellow mullein (Verbascum thapsus), are nicknamed white man's footsteps. The racial reference is justified here, because, like the white man, most noxious weeds come from Europe; like the white man, they have penetrated remote parts of our countryside. A friend who sometimes gives tours to visiting Europeans reports that the one plant they always recognize, even if they are not botanists, is that mullein. Another friend, conducting a survey along Denver’s South Platte corridor, was thrilled to find broom snakeweed (Gutierrezia sarothrae). A weed for sure, but at least a native one, it was the only native plant he’d seen all day. Talk about scorched earth: Is this the future of all our special places?

White man’s footsteps. It’s an arresting image that becomes sinister when you see mullein growing alone on a slag heap, or thriving along your favorite trail. Speaking of trails, the more we build, the more inviting entrances we make into our wilder places. Weeds will find them easily, because we and our animals will bring them along.

If it sounds like we are dealing with a dreaded disease like cancer or AIDS, that image works equally well. And the cure is similar too: prevention, early detection, and eradication. But that requires vigilance, education, and cooperation. It is easiest—and cheapest—to control weeds when they first appear in an area. Most new weeds have been here 30 years and occupied 10,000 acres before they’re even reported. But you can’t report weeds if you don’t know the weeds from the wildflowers. You can’t control weeds in your backyard if your neighbor is maintaining a seed source next door.

The spread of weeds has been compared to an explosion in slow motion. BLM, for example, has 8.5 million acres of land already infested, and estimates that by 2000, 19 million acres will have been lost if weed management efforts are not dramatically increased. BLM now allocates 60% of its weed budget to biological control, which only slows the spread—those critters can’t survive if they eliminate their food source! So, biological control, some experts say, is what you do when it’s too late. Biological control requires infestation—it won’t work when there are only a few weeds in an area. It is expensive, but it is still a necessary part of our weaponry.

On the other hand, there’s chemotherapy, the last resort. Is the cure worse than the disease? Chemophobic environmentalists, of which I am usually one, need to realize how desperate some weed situations are. No one goes out looking for chemotherapy, but we can’t afford to dismiss any effective weapon. In fact, exotic invasions are the second leading cause of today’s declining biodiversity; they are costing us the animals and plants we enjoy most. In fact, nothing can eliminate our native ecosystems as quickly and permanently as exotic infestations. One ecologist, who leads his class to a special spot for field trips, says that where 60 native plants were blooming in springs past, only two can be found now. Exotic weeds discovered his location, and the spot became educational in a whole new way.

War, wildfire, disease, alien invasions—the weed message necessarily comes to us by way of harsh words and images. Let’s listen before it’s too late.

——
Originally published in Upbeat, September 1996. Illustration by Jan Ratcliffe. All rights reserved. (Clearly the statistics need updating!)

More on mullein: A New Plant Community (mine) and Favourite Old Weed (by a fellow blogger).

Monday, October 24, 2011

Basil Coyote, Sadie Owl

We are privileged to live among wildlife. Sometimes it's also heartbreaking, but it's always a privilege. If we love living here, that can't be just because no sacrifice is required. We have to accept balance among the sometimes-conflicting things we choose to love. We learn to understand risk.

Basil was a sweet, innocent, big, gorgeous young cat we loved very much. He showed up, just appeared, one morning on the neighbor's doorstep—one tiny kitten in a light dusting of snow—and he ended up with us. Two years later, he disappeared just as abruptly. We guessed he went off to become a coyote. Paths crossed; a transformation took place. Basil Coyote. We're pretty fond of coyotes too, though from a larger distance than cats, and we had a clear idea whose rights—and whose needs—took precedence.

When my sister took Sadie to "the land" (their new home in the oak woods of southwest Colorado), she understood the risk. But Sadie was an outdoor cat, inevitably a hunter. She loved the woods, the clear fall days, but only briefly. The day after she failed to come home, my sister found herself face-to-face with a great horned owl in those same woods. She had an eerie feeling she was looking straight into Sadie's wild-hunter eyes.

Perhaps you've never been face to face with a wild owl. It's an experience you don't forget. An owl's eyes contain uncompromising wildness, more than enough to make you back up a step. The one I saw up close was hurt, but the only readable expression I caught was wariness (of me) and sharp intelligence. Not for nothing are owls thought wise. Those eyes will stay with me always. The impenetrable look of a wild predator calmly assessing ... you. (Photo by Peter Manidis, courtesy Wikipedia.)

Some cats sometimes show us this face. Cats are only marginally domesticated (part of their appeal for some; part of their horror for others). You'll never see this look in the eyes of a companion dog. One of the cats I've known is capable of this. Tame, trusting, and occasionally affectionate as he is, looking into his eyes, as into the owl's, is sounding the depths of the unknowable. It would be difficult to be comfortable with such eyes, or complacent about life while he is watching. The wild waits always.

One of my favorite books* has a story about Jumping Mouse, who wanted to explore—to see farther than any other mouse had. It is a mouse's nature to know best what is up close, to see clearly only that which is at hand. Mice are nervous and timid little creatures, and rightly so. You would be too if you lived at the bottom of so many food chains. Although he was frightened, Jumping Mouse persisted—and eventually succeeded—in his quest. He was transformed into Eagle, a being who could fly higher and see farther than most mice ever dreamed.

Transformation is a recurring theme in Nature. What goes around comes around. Cute saying: Nature invented it. Sometimes mice become cats and sometimes cats become coyotes or owls. Sometimes German shepherds become mountain lions. I don't think we have much chance of escaping this merry-go-round. We're all just reshuffling patterns. If there's anything you value more than you value the process, maybe you're living in the wrong place.

* The book is Seven Arrows, by Hyemeyohsts Storm... recommended reading! You can read the story of Jumping Mouse at the link.


Sunday, April 24, 2011

Rethinking Arbor Day

For the school child, Arbor Day is one of the unquestioned goodies of childhood indoctrination, like Washington’s or Lincoln’s Birthdays, a day to be happily and unequivocally celebrated by the planting of trees. But as the actual presidential birthdays have succumbed to our busy and efficient world of Monday holidays, perhaps it is also time to look at what Arbor Day is really about, how we came to celebrate it at all, and whether it is still a fitting holiday for today’s world.

In fact, our relationship with trees is ancient, vital, and undoubtedly eternal. It stems from primordial memories of our ancestors seeking cover and protection when threatened. Researchers have suggested that in the savannas of our species’ youth, certain trees and small woods offered refuge from the large cats and hyenas that were predators on early humans. Today, we are still attracted to such pastoral situations—open areas with good visibility, yes, but not unrelieved openness. Think of 18th century landscape paintings. It is not trees in deep woods that attract us, but smaller stands of isolated trees nestled in verdant meadows. Deep woods, in fact, add to our sense of danger and foreboding.

When J. Sterling Morton and his wife arrived in Nebraska from Detroit, unrelieved openness was pretty much what they found. The vast plains were a surprise to pioneers who had just spent several generations clearing their way through the dense forests of eastern North America. The few cottonwoods along the riverbanks were quickly depleted by a society focused on obtaining shelter and fuel, and settlers soon learned what it meant to live without trees.

From his platform as editor of Nebraska’s first newspaper, Morton promoted the planting of trees. On the first Arbor Day, celebrated on April 10, 1872, an estimated one million trees were planted. In 1885, when Arbor Day was made a legal holiday in Nebraska, April 22nd was set as the date for its observance. In his speech to a packed opera house, including 1,000 schoolchildren who had triumphantly paraded through town after their requisite tree-planting, he said

“...in picturing the heaven we long for, man’s brain has always drawn largely for its imagery from man’s vegetable co-tenants of the globe. This being man’s concept of human happiness, let us endeavor then ... to so embellish the world with plant life, trees, flowers and foliage, as to make our earth homes approximate to those which the prophets, poets and seers of all ages have portrayed as the Home in Heaven.”

Morton sought, especially, for his fellow citizens to help repair the denudation they had themselves created, as the “fifty-five millions of Americans consume daily for their varied uses 25,000 acres of forest.” (Today our number is 311 millions, and that effect has multiplied. We were only 270 million when I first wrote this article.) “We ought to bequeath to posterity as many forests and orchards as we have exhausted and consumed,” he added. Who could argue?

Here in this country, we settlers have always planted trees. We want to be in the company of trees. Growing up in rural New York state, whose original forests were decimated, we would travel the back lanes looking for old homesteads or graveyards, always spotting them by the characteristic pattern of artificially planted trees: A few Norway spruces, standing out darkly against the regrown deciduous forests native to the area; or looking closer, perhaps an old orchard, a few lilac bushes. In Wyoming, a similar pattern prevailed, with homesteads outlined by regimented windbreaks of Russian-olive. We plant trees, it seems, but we often plant exotics that instantly mark the landscape as man-made.

If you compare the way Denver looks today to historical photos, you know that things have changed significantly. And Russian-olive, once distributed intentionally for erosion control and “wildlife habitat,” is now outgrowing native cottonwoods and destroying wildlife habitat to such an extent that many declare it a noxious weed subject to eradication. This Arbor Day, as in most celebrations past, many of the trees to be planted will be exotic or ornamental introductions, especially those offered “free” by banks and others who haven’t thought through what they’re doing. Be wary. There are alternatives to remaking our landscape—we could plant more natives for example, if we must plant trees. Or we could learn to live with the prairie landscape we have. Yet, as we approach the 140th anniversary of Arbor Day, the National Arbor Day Foundation tells us, “a visit to Nebraska today would never disclose that the state was once a treeless plain.”

“Most of Earth's terrestrial ecosystems are treeless, and planting trees degrades them.”

—from Don’t Worry, Plant a Tree, by Ted Williams, Audubon magazine, May 1991

In harboring qualms about Arbor Day, one feels like a Grinch or a Scrooge. How can we not love the idea of planting trees? There’s a right way and a wrong way, a right place and, in the case of large parts of Colorado, “treeless plains.” We ought to think twice before planting, for there are many places where trees never lived and are still not needed today. Do you really want to be out digging holes and hauling water, when you could be relaxing and watching a field of native grasses waving in the spring breezes?

Not truly treeless, however, our prairies have their own arbors of cottonwoods, hackberries, chokecherries, even pines—all in appropriate places along streams or on rocky outcrops. In inappropriate places or inappropriate species, trees become a maintenance struggle, as most residents of the urban Front Range have discovered the hard way.

Eternal prairie and grass, with occasional groups of trees. Frémont prefers this to every other landscape. To me it is as if someone would prefer a book with blank pages to a good story.
—Charles Preuss, Exploring with Frémont, 1842

Although prairies do have their “good story” and their trees, they never support dense forests like those that were, ironically, destroyed by those who moved on to become born-again tree planters on the plains. The prairies had tenants of their own, tallgrasses and midgrasses, wildflowers most of us have never seen. The past tense is largely accurate, for most of the native prairie and many of its inhabitants are gone. Like the forests before, the deep-rooted true prairies that once thrived in our challenging environments were destroyed by the “sodbusters,” who then quickly learned the necessities of erosion control.

——
By Sally L. White, originally published in Colorado Gardener, April 1999


Sunday, December 26, 2010

A Harvest for the Holly Days

That holiday tradition of “decking the halls” is a long one still well practiced today. Seeing our homes and streets festooned with greenery, we might think little has changed from those nostalgic Victorian Christmases we emulate. Gathering decorative greens, however, is a rite best practiced in places where sustained harvests are possible. How well have familiar—and some not so familiar—holiday plants withstood the pressures of our seasonal festivities?

Taking the old songs seriously, we’d first observe a notable lack of “boughs of holly” in our local decorations. I’ve seen quite a few Christmases, and I’ve yet to see more than a small twig of actual holly at a time. In the milder climates of England and southern Europe, where it is native, holly (Ilex aquifolium) grows into a tree some 70 feet tall, and it is perhaps still feasible to harvest entire boughs for the mantelpiece. According to one study, regeneration of holly trees is not dependent on the seeds eaten by birds, which are deposited under trees in great numbers, because seedlings cannot survive the deep shade and high competition there.
Most successful young trees are found in well-lit patches where they are safe from grazing animals. Thus, cows may hold a key to holly’s long-term survival. Gardeners hold another: Many species of holly are also cultivated, even in milder parts of the U.S.

Ground pines, among my favorite plants, were once used to make wreaths—and may still be in lusher northern regions, such as Scandinavia. I think that most of us were born too late to see such abundance of this obscure plant in the U.S. You’ll find no red or white berries on this primitive plant—only spores. Other than decorative uses, those spores seem to be the most useful feature. They have been used for baby powder, to stop bleeding, and for flash powder for early photography. Thus the reproductive effort of these plants once literally went up in smoke.

Ground pines, also known as clubmosses, have had their day, and that day ended more than 300 million years ago. Thanks to the Denver Museum of Natural History, we can imagine what these ancient trees of the coal age may have looked like. These plants invented trees—and forests! Lepidodendron, the “scale-tree” as one example, was more than 100 feet tall, and grew in dense forests in the equatorial swamps then prevalent across North America and Europe. They, too, eventually went up in smoke; the vast coal deposits these prehistoric forests formed have kept entire countries warm for decades.

Now those ancient giants are gone, and only about 450 species of their lowly relatives survive. Most survivors belong to the genus Lycopodium, or wolf’s foot to Greek enthusiasts. We have few species of Lycopodium in Colorado; most abundant, though hardly common, is the unusual Lycopodium annotinum, stiff clubmoss, growing on the West Slope in small patches. This species occurs from Greenland to Alaska, where it is found in mature forests, especially those not disturbed by logging for many decades, and is occasionally eaten by moose. It is ranked S4, "apparently secure", in Colorado; very secure in much of Canada. Another species, L. alpinum, is "critically imperiled" in Colorado and Newfoundland, but rated apparently secure in the Yukon, British Columbia, and Alberta. (Photo by Franz Xaver from Wikipedia.org).

Are the remaining clubmosses on the way to extinction? If so, it may be that we have helped them down that road a bit. In moist forests of turn-of-the-century New England, ground pines were harvested in great volume for wreath material and other hall-decking. As a child in the northeast, I remember these wonderful plants but never found them in great abundance. About six inches tall at most, spreading outward in patches under the trees, these plants do resemble miniature pine trees. As with most “useless” plants of the forest floor, they are rarely discussed in forestry studies and rarely thrive in managed forests and tree plantations. In New York today, lycopods are protected on public lands, as they all, as a group, are considered to be declining and vulnerable to exploitation, in part because they regenerate very slowly after being harvested. Commercial collecting has made some species rare; the L. complanatum I remember is now considered "critically imperiled" in New York State, but L. obscurum remains secure there. [Explore the status of species of Lycopodium at NatureServe.org.]

Our wreaths and boughs today usually substitute easily gathered pine, spruce, and fir branches for these older plants. Some of us may be able to harvest boughs from our own backyards; most of us probably cannot. A few commercial collecting permits are offered in our nearby national forests; the Arapahoe-Roosevelt Forest this year [1996] sold commercial permits for about 8 tons of boughs at $50 per ton. (If you have a permit to cut a Christmas tree, you are allowed to pick up a few boughs for personal use.) Decorative boughs for wreaths and garlands are harvested from private lands in Colorado as well.

Some coniferous decorations offered for holiday sale here and elsewhere in the U.S. are imported from the Pacific Northwest, where trees are larger and grow more quickly. In the Wenatchee National Forest in Washington, more than 90,000 pounds of limbs and boughs were harvested in 1995, along with 500 bushels of cones and 2,500 pounds of other “foliage.” Perhaps some of this year’s harvest—regional or imported—will end up brightening your own front door.

——
by Sally L. White, originally published in Upbeat, December 1996, ©2010.


Saturday, November 13, 2010

Do Sleeping Plants Dream?

Disclaimer: It amazes me that this essay was written more than 14 years ago. Since then, science has indeed marched on, and an update on nastic movements is now posted over at Foothills Fancies.

My new prayer plant is an early riser. Although the sun is below the horizon and the room is dark, the sky is lightening, and she is already wide awake. How do I know? Well, some plants are dramatic in their daily movements, and her species is one of many that have attracted attention for centuries because they give the appearance of waking and sleeping each day. Pliny the Elder, a Roman scholar circa 75 A.D., remarked on the somnolent plants; much later Linnaeus devoted a famous essay, Somnus Plantarum, to the subject.

When I set out to write this essay, I wanted an appropriate subject to observe, and lo! not one of the 50+ houseplants in my current collection is this visibly hyperactive type. In my search I came first upon a prayer plant (Maranta leuconeura), although I might have found a dainty shamrock (Oxalis spp.), often available this time of year. If I were very lucky, I might even have encountered a sensitive Mimosa, a faddish plant that periodically disappears from the horticulture trade as each generation tires of touching them to watch the leaves collapse. (These days it may take more to amuse us, for I haven’t seen a Mimosa in years.)
Photo of Maranta leuconeura, awake!, by Kurt Stueber. From BioLib.de, Creative Commons, GNU Free Documentation License, accessed from Wikipedia.

But I shall have to get up early indeed if I expect to see this plant in action, her leaves unfolding from her nightly prayers to spread themselves in anticipation of the light. Trying again, I find that she is prepared even before the first hint of light appears to my eye, although she was sound asleep when I went to bed. In his study of plant movements, Charles Darwin observed dozens of plants that raise or lower their leaves in sleep. These plants don’t respond to light alone, he found, but to the cycles of light and dark, the difference between intense light and its absence. Plants need strong light and good moisture conditions to demonstrate sleep behavior. Plants that are stressed or disturbed, as his Maranta was by strong wind one night, remain sleepless for some time thereafter.

Typically thorough, Darwin lists sleeping species in 86 genera belonging to 26 distinct plant families, although the legumes have by far the most. Sleepers include species of lupines, milkvetches, sweet clovers, wild licorice, and many others whose relatives grow wild here in our foothills, as well as tamer ones like hibiscus and cotton, common garden beans and radishes, nasturtiums, four-o’clocks, and morning glories. Sleeping plants...it’s a charming concept that modern scientists tersely labeled nyctinasty (from Greek roots for night and pressing close), then mostly ignored.

Tracing the movements of individual leaves day after day, Darwin concluded that sleep movements are a modified form of the normal—though far less obvious—movements healthy leaves continuously make. How can a plant with neither muscles nor nerves move so quickly? You’ve probably noted that leaves are capable of abrupt position changes when they run low on water. We call it wilting. Most nastic movements are also based on hydraulic changes within the cells. By raising or lowering water pressure on opposite sides of the leaf stem, a leaf can move through angles of 90 degrees or more, and even turn on its axis. Some plants, such as my Maranta, are equipped with specialized joints that control their daily movements. These structures, called pulvini, occur where the leaf blade joins the petiole, functionally a bit like the wrist joint connecting your hand and forearm.

By forcing some leaves to stay “awake,” Darwin also tested whether plants are protected from cold nights by their cozy postures of sleep. It’s not the cold wind that’s the threat, he tells us, but radiation—a subject we tend to overlook. On clear nights, any exposed surfaces will lose heat directly to the open sky—to space, as it were. By folding up or down in sleep, leaves turn their narrowest edges to the sky, protecting their broad flat heat-losing surfaces. According to his experiments, leaves thus protected were less often damaged by frost. If sleeping offers such advantages, why don’t more kinds of plants—especially those in cold areas—sleep?

Well, they do, don’t they? Most of our local plants are deep in a season-long sleep, leaving only tropical houseplants to keep us company through the long deprivations of winter. While these companions keep us in touch with the spirit of plants, they also fill our shuttered houses with good green oxygen and remind us of spring. “Storms and winter weather,” some say, “bring plants and people close together.” We probably have a few storms yet to weather this winter, and can rely on our faithful houseplants to help us get through them.

Although we have an extensive leguminous flora, I’m embarrassed to admit I’ve never caught one of them asleep. So when spring does come, I plan to take some walks at dusk, just to see if I can spot the “jerky movements” Darwin speaks of, and to see how many native cousins of the greenhouse plants he studied also sleep. Darwin noted in his classic understated style, “It is troublesome to observe the movement of leaves in the middle of the night,” although he did so nonetheless. Can such inconveniences explain why the fascinating sleep of plants is so little studied now? In his later years, although he rarely left his home grounds—or sometimes even his study—his curiosity and patience yield us marvels to contemplate more than a century later.

——
by Sally L. White, originally published in Upbeat, March 1996, ©2010.


Tuesday, June 01, 2010

A Light in the Forest: Aspens and Fire

The morning after fire, burned soils are slowly cooling. Lodgepole pine seeds drift down from cones opened by the intense heat. Light breezes stir the layer of ash on the ground. Survivors—birds, mammals, and other forest life—are already seeking new homes. The forest is quieter today and smells strongly of fire. For us humans, fire is a terrifying and uniquely threatening experience—one we cannot always control or appreciate. We see only a charred landscape, and grieve. But while we continue grieving, nature simply begins again.

Already the shallow lateral roots of aspen are feeling the effects of auxin deprivation. The aboveground stems, now absent, no longer send their chemical message of living trees above, a message that has held potential new shoots at bay. Thousands of tiny buds, the primordia of aspen trees to come, are awakening to start the long process of recovery. Long, that is, by our standards. In the life of a forest, events will proceed quickly. In a year or two, there could be thirty young shoots for each mature stem that existed before the fire. Within 20 or 30 years, superficial evidence of fire disappears, leaving the aspen themselves as the primary clue.

In an aspen woodland, the life below ground is older than the forest we see, and it may well have seen fires before. In fact, aspen has an ancient relationship with fire, but it is an unusual one. With a lifespan comparable to ours (say 60 to 120 years), individual stems of aspen are short-lived as trees go. The forests they create thrive on the rebirth that fire provides. That is, until we came.

Today, aspen forests are as often rejuvenated by logging as by fire. Any method that removes the overstory trees without damaging the all-important root system is effective. In fact, researchers have found root density to be a key indicator of successful regeneration in aspen stands. Too few roots, and the aspens give way to grasses or conifers.

Of all the forest types adapted to fire, aspen is the least flammable and in many ways the most dependent on fire. Our other forests—of ponderosa pine, spruce and fir, or other conifers—burn more readily. In most seasons, aspen forests are either snow covered or too green to carry fire, and may even act as a firebreak, slowing or stopping fires that reach them. This trait is used to advantage by firefighters. In fall, however, when the lush understory has been killed by frost and the thick layer of aspen leaves has dried to a fine tinder, then aspen can burn and burn brightly.

Most fires in aspen woodlands occur in October under just such conditions. Such fires during the mid- to late-1800s gave us the aspen glories we drive to the mountains to enjoy today. We have so few deciduous trees: what would we do without the golden glow of October's aspen? Some years, extra hot and dry, give us Octobers to watch with caution, mindful of the long-standing relation between aspen and fire.

That dependence of aspen on fire has its own dynamic. Although they need fire, aspen forests are very vulnerable to it. Individual stems, with their thin bark, are girdled and killed by even moderate fires, but remember that the deeper life is underground. The parent root system must start over, each time, from scratch. Even a severe fire kills lateral roots only in the top two inches of soil. Suckers can sprout from laterals five to six inches deep if necessary.

If fires are too frequent, however, the roots will be exhausted from the efforts of renewal. If fires are too rare, occurring at intervals of more than a century or two, the aspen may grow old and die out beneath a dominant overstory of conifers, leaving no roots to replenish the site. Fire every 50 to 100 years is about right for continuous aspen, if that's the goal.

In comparison, ponderosa pine forests use a different strategy to achieve persistence through time. Frequent fires, every five to twenty years or so, thin the understory while individual trees live on, encased in their protective layers of bark. Fire delayed is made deadly. As we live with and in Colorado's forests, we are not required to choose whether or not we will have fire: we will. Our challenge is to decide whether we prefer fires to be frequent—or intense. Choose wisely, be careful, and enjoy the gentler side of aspen's October glow.

——
Copyright, S.L. White, 2010. Illustration copyright Jan Ratcliffe.
Originally published in Upbeat, October 1994.


Thursday, February 25, 2010

Let the Birds Do It!

Each spring for a few weeks I get the urge. I study seed catalogs and linger longingly at nursery displays. Sometimes I even succumb to the lure of bright flowers and elegant shrubs. But despite my fantasies, I have yet to achieve the perfection and visual charm I so often see portrayed as The Ideal Garden.

Two things conspire against me. One, our semiarid climate, seems to be a barrier between my wild, unruly yard and the delicious pictures I see in the gardening or lifestyle magazines. I know that such designs are made for eastern gardens or other places where water can be used profligately. The second controlling factor, which prevents us from ignoring the first and simply spreading water everywhere anyway, is our 400-foot-deep well. Barely adequate (with care) for the two of us, it is not enough to support a traditional garden in the style it prefers. Our yard has been called an extreme Xeriscape test garden—if it can grow here, it can grow anywhere. We’ve tried out many plants, and it is a limited set indeed that can master our inhospitable circumstances.

There is a third factor, no doubt. My own laziness, or perhaps readiness to be distracted by other demands, creates an inability to focus on the garden’s needs and contributes to my sense of failure. So I have had to find another route to (limited) success—I have recruited the birds to my aid. If I want a garden that provides habitat for wildlife, what better approach than to take advantage of the birds’ tendency to improve their own habitat? This generates a serendipitous garden that is less about control than about spontaneity. A garden that continually surprises the so-called “gardener” with new developments. A garden that evolves in harmony with the animals and plants that live within it and is “designed,” so to speak, to meet their needs.

One year I noticed a clump of chokecherries (Prunus virginiana, Padus virginiana) getting started at the end of the driveway, and that was the beginning of gardening by birds. When the peach tree, long suffering from that oozing rot they get, finally died and we cut it down, I found an outline, almost a ghost, of it on the ground. Reflecting the branching pattern above were rows of chokecherries and three currant bushes. This thicket now includes a golden currant (Ribes aureum) and two wax currants (Ribes cereum) there in the back yard, planted by the birds to their own accidental pattern, and the peach tree’s memory lives on in them. If selecting the right site for each plant plays an important role in its survival, who knows better than the birds where their favorite plants will do well?

Real gardeners often look askance at “volunteers.” Letting plants spring up where they will violates their sense of design. In our yard, these plants aren’t really volunteers, they’re recruits. It’s the birds who have recruited their preferred fruits and berries.

Judging by what we get, chokecherries are high on their list, and juniper berries are popular. Currants, of course, also get their attention. (Golden currant, photo left.) These plants operate by providing a juicy, tempting, nourishing treat, the fruit or berry, wrapped around a hard, indigestible seed. If you’ve wondered why blackberries (including raspberries, thimbleberries, and other relatives) pop up along fencerows and under streamside thickets, think about where birds spend their time. More than a hundred species of animals, including grosbeaks, orioles, tanagers, towhees, grouse, and robins among the birds, take advantage of these summer fruits.

Species that provide edible seeds are using a different principle, sacrificing many seeds to the cause of dispersal, but berries and stone fruits attract birds and other animals to their purposes without such losses of valuable seed. Wild plum (Prunus americana), another native I’d like to have, is too large a fruit, too large a seed really, to be carried by birds, and has yet to appear here accidentally.

There are two approaches to accidental gardening: one is to let the birds do it, and live with the results. You’ll find seedlings under bushes and trees, along fences, and even under telephone wires. My husband suggests that perches strategically placed around the yard would help fine-tune this haphazard process. Another way is to let the birds create a nursery for you. We have a large oriental elm in the backyard, a beautiful tree from an unfortunate species, but the birds enjoy perching on its branches. Underneath it, we find a flock of juniper seedlings that will tolerate its shade for a while, but won’t do well there in the long term. So we transplant them to sunnier locations once they’ve gotten off to a good start. This nurse tree approach can often be observed in the wild, but there the survival of the young plants often depends on the timely demise of their nurse.

Other species we’re keeping an eye out for are the vines: wild grapes (Vitis riparia) and western woodbine (Parthenocissus inserta) have berries that ripen and stay on the vine late in the season, providing fall and winter food for many species of birds, including woodpeckers, chickadees, bluebirds, and waxwings. Snowberries (Symphoricarpos spp.) could also pop up, as they too provide winter food for many species. All will be welcome.

When you let the birds help with your landscaping, you will not only be providing them a feast, but will enhance their nesting sites and protective cover, as well as giving many other animals food and home sites, from deer and rabbits to coyotes and bears, allowing you many more surprises in the garden!

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Copyright, S.L. White, 2010. Illustration copyright Jan Ratcliffe.
Originally published in Upbeat, June 1997.