A Garden of Marvels Page 18
It appears from my Internet browsing that Leyland cypresses are not easy to kill. Simply chopping down the beasts doesn’t slay them: Their stumps, hydralike, quickly generate multiple new sprouts. One Internet poster suggested coiling a soaker hose on the soil around their trunks and leaving the water on (for how long, he didn’t say) to drown the roots. Several others suggested spreading a heavy dose of rock salt on the ground, killing them à la Carthage.
That cypresses would be hard to subdue makes sense. Leylandii is a member of Coniferales, a division of woody trees that emerged late in the Carboniferous to take advantage of the new, deep soil. Conifers have survived ever since, through hothouse and icehouse climates, moist and arid conditions, mountain upheavals, and several catastrophic asteroid collisions that killed off many less hardy species. Most of their primeval companions have long gone extinct or been reduced to tokens of their former selves, but conifers are represented today by some 630 species. Some of the world’s most venerable specimens of trees are conifers, including the tallest living tree (a 380-foot Sequoia) and the oldest tree (a five-thousand-year-old bristlecone pine). Even older, in a sense, is a spruce growing in Sweden. The visible portion of the tree is only thirteen feet high, but its root system, which sends up a new shoot to replace the old one (after six hundred years or so when it dies), has been alive for more than 9,500 years.
Conifers are gymnosperms (JIM-no-sperms), a new group of plants that evolved in the late Carboniferous. Instead of reproducing via spores, gymnosperms had seeds. Spores are single cells. Seeds, on the other hand, contain embryos—open up a fertilized and ripe seed and you may see an embryonic root, shoot, and a leaf or two—inside a multicellular seedcoat. The seedcoat also encloses a stash of carbohydrates, the endosperm, that the embryo uses to grow before its leaves develop sufficiently to gather solar energy. But while the gymnosperms had larger, more complex seeds, they had to sacrifice more of their stored energy to produce them. Consequently, they couldn’t afford to produce as many seeds as ferns produced spores, although any individual seed was more likely to thrive than any single spore.
At first, this trade-off was a viable, if not an overwhelmingly successful, strategy. The earliest conifer species were small, and some looked much like that common, often rather spindly houseplant, the Norfolk Island pine. They had similar needlelike leaves and sparse, resinous branches that extended in a whorl from a slender trunk, although their cones were more primitive. From the end of the Carboniferous and through the Permian (about 300 to 250 million years ago), a handful of conifer species persisted. Then, suddenly, at the end of the Permian, the Coniferales exploded in number and diversity, and came to dominate the Earth’s flora.
A Norfolk Island pine.
Why? First, a geologic accident that had been waiting to happen, happened. The planet’s continents, always moving on tectonic plates, collided to form Pangaea, a supercontinent that stretched from one pole to the other. As a result, ocean circulation patterns were interrupted. Sea levels dropped as glaciers formed at both poles, and the shallow, warm continental shelves, once full of diverse marine life, became land. Around the equator, the many inland lagoons and swamps dried up entirely, replaced by sand dunes. Land in the mid-northern and mid-southern latitudes became temperate, and as is the case today, had seasons, including chilly winters.
Next, it seems that an asteroid six miles wide and the mass of Mount Everest slammed into the Earth off the coast of northwestern Australia, creating a 125-mile-wide crater and adding massive amounts of light-blocking dust to the air. Unable to photosynthesize in the haze, plants and algae died, thereby starving many of the marine animal, amphibian, reptile, and insect species that depended on them. Then, massive volcanic eruptions in Siberia spewed out lava that covered at least 1.5 million square miles, an area larger than Europe. Because the lava erupted through the largest coal basin in the world, large amounts of carbon dioxide and sulfur dioxide rushed into the atmosphere, trapping heat and causing dramatic warming. The trapped gases melted the permafrost and heated even the frigid seabeds, which in turn belched sequestered methane, an especially potent greenhouse gas.
The sequence of these events and their relative importance is debated, but there is no question about the outcome. In whatever form and order death arrived—gas poisoning, freezing, burning, starvation, suffocation, and dehydration—we know that life was decimated within a two-million-year period, a blink of a geologic eye. The catastrophic confluence of events is called the end-Permian extinction or, colloquially, the Great Dying. Ninety-six percent of all marine species went extinct; at least 90 percent of all life on Earth died. Earth at the end of the Permian and the beginning of the Triassic (250 million years ago) was, in most places, hot and dry, with shockingly reduced biodiversity.
Only one family of conifers survived the Great Dying, but that family, the Voltziaceae, was well positioned to thrive. Its needles were perfectly suited for the hot and dry climate. They had a small surface area and were heavily coated in a waxy substance that resisted desiccation. Their stomata were sunken into the needle’s surface to further limit evaporation. Because the concentration of carbon dioxide in the atmosphere had increased, they were nonetheless able to access sufficient amounts of the gas. The conifers thrived, radiating into multiple families and at least twenty thousand species. Many were tall (some up to two hundred feet tall, three times the height of an oak) with short branches radiating from top to bottom, and looked like gigantic bottlebrushes; others, like modern sequoias, were tall with thick trunks sporting stiff branches only at their summits. Some evolved to cope with high salt concentrations as mangroves do now; others, in order to survive on flood plains where any individual’s life was short, set cones in a season or two. A few species had the Christmas tree shapes reminiscent of our spruces and firs. By about 200 million years ago, conifers dominated the land, comprising about 50 percent of the world’s plant species.
Then, in the heyday of dinosaurs about 140 million years ago, something new under the sun appeared. The first plants with flowers—the angiosperms—evolved in the tropics, diversified, and expanded their domain rapidly. The secret of their success was their leaves. Broad and flat, they had a greater surface area that gathered more sunlight than the narrow-bladed conifers. The level of carbon dioxide in the air had fallen, and these new leaves could access more of it. Making more sugars, they could grow faster, especially as seedlings and saplings, and they shaded out the slower growing conifers. Conifers eventually ceded great tracts of territory, surviving primarily in those regions too cold for most angiosperms or in poor soils that couldn’t support angiosperms’ high demand for nutrients. Today, 75 percent of all species are angiosperms, conifers are 15 percent, and pteridophytes—ferns, horsetails, and club mosses—comprise the remaining 10 percent. The largest concentrations of conifers are in mountainous areas, the far latitudes, and in rocky, clayey, or acidic soils.
Among the remaining conifer species are two natives of North America: the Monterey cypress and the Nootka cypress. The former grows wild only around Monterey and Carmel in California, along the cool and rocky coast. It is that iconic wind-sculpted and twisted form often photographed half obscured by fog. The few specimens, some two thousand years old, are all that are left of what once was an extensive forest. The Nootka has a traditional pyramidal profile and distinctive foliage that droops in sprays from its branches. It grows in high altitudes along the coast from northernmost California to southern Alaska.
On the left, a Monterey cypress; on the right, a Nootka cypress; in the middle, a Leyland cypress, a sterile hybrid of the two.
These two august species are the parents of the Leyland cypress, a sterile cross between the two. The pair never would have met in their native habitats: The southernmost Nootka grows four hundred miles north of the Monterey range. But in the mid-1800s, Christopher Leyland, a banker in Liverpool, gave his nephew John Naylor an estate in southern Wales as a wedding present. At great expense, Naylor renovate
d the house and hired a landscape architect to lay out gardens. The architect installed a variety of exotic trees, including the Monterey and Nootka, which he planted in close proximity. In 1888, a hybrid seed sprouted and grew. The next year, Naylor died, and his son Christopher inherited the estate and changed his surname to Leyland. Christopher Leyland took six seedlings to his own property in Shropshire, where they rapidly grew into large trees, Cupressocyparis leylandii. Because Leyland cypresses are sterile, the specimens that straggle along at the edge of our yard are the direct descendants, by cuttings, of Christopher Leyland’s trees.
Of course, I never attempted to kill my neighbors’ Leylands; a premeditated murder is beyond me. Besides, large trees evoke in me—and myth and folklore tell me I am not alone—a deep-seated reverence. In any case, I know that leylandii are not long-lived, and the ones next door are approaching their natural end. In fact, my neighbor has anticipated their demise, and just inside the row of trees he has planted a long line of shrubs. The shrubs are Nandina domestica, a flowering species that should grow into a well-behaved, six-foot hedge. Which means that right here in Maryland I will be witnessing a reenactment of ancient history, as angiosperms replace the conifers.
twenty
Amazing Grass
Some midwinter day when you’re in the grocery store, pick up a few boxes of cherry tomatoes and read the labels to see where they were grown. Most come from Mexico. That makes sense: warm climate, long hours of sunlight. Others are from Canada, grown in greenhouses. The strange thing is that both boxes are about the same price. How can a Canadian grower who must pay for heat compete with the Mexican grower who gets all his therms for free? In the summer of 2011, I set out to find the answer at Pyramid Farms in Leamington, Ontario, where owner Dean Tiessen has thirty-seven acres of vegetables under glass roofs. As soon as I pull into the farm’s office, having driven about an hour southeast from Detroit, Dean bounds out to greet me. He is a fit and handsome man in his mid-forties with a straight-up shock of dark hair.
If anyone has farming in his blood, Dean does. His forebears were Dutch Mennonite farmers invited by Catherine the Great in the 1760s to settle and modernize farming in southern Ukraine. There they stayed, farming lucratively generation after generation, until the communist revolution in 1917. Dispossessed by collectivization, his grandparents fled to Canada and settled in Leamington, where, on one and a half acres, they grew seedless cucumbers and tomatoes in greenhouses. The farm passed to Dean’s father in the 1950s, and about ten years ago Dean, his brother, and two cousins took over. They transformed a small operation that sold into the local market into a business that supports three families, employs more than a hundred people, and sells across North America. Pyramid Farms now competes in a highly price-sensitive, global market.
So how does a Canadian succeed? Dean slides open a greenhouse door to show me. Forget tomato bushes. I am looking into an eight-foot-tall solid wall of tomato vines that extends the sixty-foot length of the greenhouse. It is densely hung with tomatoes, the largest, reddest ones toward the bottom, little green ones at the top. I peer through the wall, and see another one just a few feet behind this one. Dean tells me there are about a hundred tomato walls—he calls them rows, but that doesn’t do justice to their bulk—in each greenhouse.
This is tomato growing at its most intensive and efficient. We look at the base of one wall. Forget soil. Two tomato vines, thick as ropes, emerge every foot or so from a foam block set in a narrow trough in the concrete floor. A black umbilical cord of water and nutrients runs into each block. Far above, a horizontal wire runs the length of the greenhouse just below the ridgeline. Spools of string hang down from the wire every few feet. Each vine is assigned its own string and has been trained to grow up along it. Every two weeks, the spools move farther along the horizontal wire and unwind about two feet of string. Every week, a worker on a lift twirls a newly grown length of vine up the bare string toward the overhead wire. The tip of each vine grows farther and farther from its base. Eventually the tips will be sixty feet from their roots. The lengthening of the strings effectively lowers the older portions of the vines, so that great ropes of parallel, leafy, tomato-filled vines slope very gradually from floor to ceiling.
Eventually these vines will grow to sixty feet in length.
At the top of the vines, new leaves and a cluster of little yellow flowers emerge. I run my eyes down a vine and count eight clusters of tomatoes. The tomatoes in the topmost cluster are small and green, and each successively lower group is in a greater state of ripeness. By the time the tomatoes are perfectly ripe and bulging, they’re about knee height. The low drone I hear in the greenhouse comes from air circulation fans, but it could be the thrum of tomatoes growing at full throttle. Every leaf in here is green and healthy; every fruit is blemish-free.
Dean tells me he can now grow as many pounds of tomatoes in one acre indoors as his Mexican counterparts can grow outdoors in forty-seven. In the last ten years, he has tripled production per acre, thanks to improvements in greenhouse technology and the breeding process. He also has refined his crop selection, choosing to grow only specialty tomatoes—including twenty-six varieties of heirlooms—that have higher profit margins. The only variable he can’t improve is the Canadian climate and his concomitant need for fuel. About 40 percent of his cost of production is energy, and he feels the pain of every penny increase. More than any other worry—competition, blight and bugs, labor costs—it is the volatility of energy prices that keeps him up at night.
“My father burned coal to heat the greenhouses until 1967,” Dean tells me. “Then oil refining became a business in the Port Huron area, and he burned ‘bunker oil,’ the thick oil left at the end of the refining process. By the time I got involved in the business, the infrastructure for natural gas had arrived, and I kept switching between gas and coal, going back to coal when it was cheap. Then, in 2002, all fuels skyrocketed. Our heating costs went from thirty thousand dollars an acre to one hundred thousand dollars in one season.
“The situation was dire, and I looked around for any alternative, and ended up moving into wood. There’s no forest around here, but I found construction debris that otherwise would have ended up in a landfill. Every time I saw someone tearing down a building, I was there asking if I could haul away the lumber. For a while, it was fantastic: I saw my energy costs drop to twenty thousand dollars an acre. But soon everyone was going after the stuff, and builders stopped giving it away. It became a commodity. Then it got scarce, and the price went way up. Fortunately, by that time coal had become cheap again. Right now I’m burning natural gas.”
About five years ago, Dean explains, his inability to get “a line of sight” on future fuel costs and his experience burning lumber inspired him to look into biomass for energy. If he could grow his own fuel, he might fix his long-term energy costs and sleep better. Maybe, with fixed energy costs, he could offer longer-term sales contracts for his tomatoes, which would attract buyers. And he figured that if a cap-and-trade system for carbon emissions ever develops, as it has for sulfur emissions, he could sell his carbon credits.
In 2006 he took a tour of European biomass farms. The English and the Germans had more varied experience with growing biomass than North Americans, who were focused on fermenting corn into ethanol to supplement gasoline. He stopped in on farmers cultivating willows and poplars, Japanese knotweed, switchgrass, and miscanthus. Knotweed turned out to be an invasive species in the United States, and therefore a nonstarter. Willows and poplars, while fast growing for trees, nonetheless take thirty years to get to harvest. In the interim, the crop could be devastated by disease, insects, or fire. Switchgrass, a perennial grass native to the North American plains, was an interesting possibility. But even more attractive was miscanthus, a perennial grass native to Asia and Africa. In Germany, researchers were having success with a hybrid called Miscanthus giganteus, a variety that grows as tall as twelve feet, and produces at least twice as much biomass per acre as s
witchgrass.
In Dean’s eyes, the crop had additional attractions. Not only is it a perennial; it has proved to be particularly persistent. He saw experimental plots in Germany that had been growing for two decades. In Japan, where miscanthus has been cultivated for centuries as roof thatch, some stands are two hundred years old. Because giganteus is a sterile hybrid, it couldn’t go to seed and escape his farm and invade his neighbors’ fields. Nor would it, like kudzu, colonize by creeping: After twenty years, Danish experimental stands have expanded by only a few feet. If the crop didn’t work out, it would be easy to uproot. Pests have no interest in its tough leaves, and after the first year, it grows so tall so quickly, it shades out its weedy competitors. Miscanthus can remain in the field, straw-colored and sere, until late fall or even spring, when idle harvesting and baling machines can take it down. The longer it stands in cold weather, the drier—and the better for burning—it gets. Bales of miscanthus can be left in the field for months without degrading, so there would be no storage costs.
Unlike the corn grown for ethanol in North America, miscanthus grows well on marginal land too steep, too sandy, or too low in fertility to grow row crops. In the late fall, as it stops photosynthesizing, it sends the nutrients in its stalks and leaves back underground, which means a field of miscanthus needs few or no costly fertilizers. And giganteus is unpatented and freely available. The only downside seemed to be that no one had yet figured out how to plant it efficiently, so initial planting costs would be high, but Dean figured he could overcome this. On his return from Europe, Stephen Long, professor at the University of Illinois and one of the world’s leading miscanthus researchers, gave him five rhizomes to try in Ontario.