The two anatomists changed the way people conceived of plants. Until their books appeared, people considered plants to be an amalgam of parts. The relationship among the parts was . . . well, no one imagined there was much of one. A plant was a kind of Mr. Potato-Head, with roots screwed on like shoes, branches attached like arms, and leaves stuck on toward the top like his eyebrows or hat. When they discovered that the same parenchyma makes up roots and leaves and fruits, and that vessels extend from the tip of a tree root, through the center of the root, up the perimeter of a trunk and out its branches, and into the smallest veins of leaves, a plant made sense as an integral whole. No one would improve on their anatomical work for 150 years.
Despite their accomplishments, however, neither man achieved as much as he had hoped at the outset. Grew had proposed an immense program of research in his Anatomy of Plants Begun, of which delineating structure was only the first step. He wanted to understand how plants grow; how seeds are formed, germinate, and send out roots; how “the aliment by which a plant is fed is duly prepared [and] conveyed”; and what causes seasonal changes and what makes colors in flowers, among many other questions. Like Malpighi, he expected that understanding the “how” of plants would shed light on the “how” of animals, including man. But, in fact, they were able to explain very little of plant, much less animal, physiology.
Their failure is not surprising. Their microscopes lacked sufficient magnifying power, for one. Their propensity for analogizing from animals to plants (despite the presumption that it was plants that would shed light on animals) led them astray, too. Malpighi thought he saw peristalsis, the wavelike motion that moves food through the human alimentary canal, in the vessels. Expecting to find organs that served as bowels and lungs in plants, Grew thought vessels, new and “antiquated,” were responsible for digestion and breathing. The problem was that uncovering the physiology of plants would take more than meticulous observation. It would require experimentation.
PART II
Roots
six
Restless Roots
One July afternoon more than two decades ago, when our oldest two daughters were two and three, I looked out the kitchen window and saw the western sky had turned a strange and inky green. Usually, I enjoy the drama of a summer thunderstorm, and appreciate the reminder that nature is a powerful force even in our tidy suburban landscape. But this was a storm of a different color, and some marrow-deep instinct told me to find a safer refuge. As a patter of rain escalated into a barrage and the wind churned the treetops to a froth, I hoisted Austen on one hip while I guided Anna down the stairs to our unfinished and windowless basement, turning on the lights and closing the door behind me. I sat on the bottom step, my arms hugging my toddlers close, facing away from whatever was out there. The weather moved in with a staggering roar I’d never heard from weather before. Abruptly, without the usual flicker, the lights went out, and we were in absolute blackness. The staircase, just open treads nailed to two stringers, vibrated: The four horsemen were galloping close by.
Only a few minutes later, the noise began to recede as the storm thundered its way east, and I could see a gray line of light at the bottom of the door. The three of us clambered up the stairs and went into the living room to look out the French doors into the backyard. At first, the rain was coming down too hard to see anything, but as it slackened and a view gradually materialized, I was stunned. Our yard had disappeared. Instead of a lawn, Ted’s vegetable garden, and the metal swing set, I was looking into a solid mass of leaves and branches. The broad crown of the Hansons’ sixty-foot sweet gum tree had fallen directly toward our house, its topmost branches no farther than six feet from where we stood. And when I opened the front door, I was greeted by another new landscape. Our street was blocked by at least three fallen trees, their limbs tangled with telephone and electrical wires. I could see houses on Oak Lane that I’d never seen before. A neighbor’s maroon station wagon had been crushed under a downed branch like an empty Dr Pepper can.
I hiked the neighborhood the next day. Dozens of trees—tulip poplars and maples, especially, but also oaks and other species I didn’t recognize—many of which had stood for a hundred years, had been toppled and were lying on the ground pointing east. To everyone’s amazement and relief, no one had been injured. The meteorologists’ diagnosis was a microburst, which occurs when a column of cold air plunges from the upper atmosphere during a thunderstorm. (When a microburst hits the Earth, it rolls outward, creating a tsunami of wind powerful enough not only to topple trees but to dash airplanes to the ground. A tornado sends trees sprawling every which way, while the wave of air from a microburst mows them down in one direction.) It would be ten hot and humid days before we regained power. Chain saws shrieked and growled for weeks.
Before a tree service came to dismantle the downed sweet gum in our yard, the girls and I went to the Hansons’ to look at the base of the trunk. At right angles to the ground was a massive platter of soil from which emerged an ugly tangle of arthritic-looking roots. I felt faintly embarrassed staring at the tree’s exposed nether region, as if I’d glanced into a hospital room and seen an unconscious patient with his gown hiked up. Still, I was fascinated by what I saw, or rather what I didn’t see. Where was the giant taproot I expected? In fact, hardly any roots emerged directly below the trunk, just where I thought they should be to anchor the towering mass above. Instead, not only did most of the roots radiate outward from the base of the trunk like some Jurassic tarantula, they clearly had been no more than a foot or two beneath earth. Moreover, none of the roots was as substantial as I imagined; they were closer to the diameter of a man’s forearm than a thigh. Of course, there had to be lots of root ends left in the earth, but they would be even more slender than what was exposed. I had to wonder: How had this sixty-foot giant with its huge, wind-catching canopy stood upright in even a light breeze? I could understand the mechanics of a banyan tree. It has a massively broad trunk to start with; then it drops aerial roots from its branches that thicken over time and prop up those branches. Mangrove trees I’d seen in Florida seem well designed, too. Their roots arc from a spot a few feet up the trunk into the swamp, acting like flying buttresses. But these neighborhood trees were a puzzle.
A good number of our neighbors were clearly also troubled by the uncertain mechanics of roots. In the years following the microburst, I frequently heard the sound of chain saws, and later would notice another gap in our ever-thinning canopy. In most cases, the trees were healthy; it was the homeowners who were worried sick. (So many were taken down that, ten years ago, the neighborhood council passed an “urban forest ordinance” that limits the removal of healthy trees.) We bucked the trend and bought a scarlet oak sapling to replace the sweet gum, and planted it at the back fence line. Our new tree wouldn’t be tall enough to pose a danger for decades. I figured I wouldn’t have to concern myself with roots for a long time to come.
As it turned out, I had only a few rootless years. My father retired early, and my parents put their house in Baltimore up for sale. To their frustration, no one offered close to their asking price, and after a year, unwilling to be anchored a moment longer to suburban life, they set sail, literally, for parts south. In their wake, they left their real estate agent with my telephone number and me with a notarized power-of-attorney in case a buyer should appear.
Back in the 1950s, when my newlywed parents moved into their newly constructed ranch-style house with its newly seeded lawn, the builder had put in two silver maple saplings in the front yard. The trees, named for the pale gray underside of their green leaves, grew quickly. But although the shade was welcome and the leaves, which shimmered in the lightest breeze, were beautiful, the ground beneath their canopies was a disaster. Silver maples have notoriously extensive and shallow roots. When I was in grade school, the roots had already crumpled the asphalt driveway. (My mother encouraged me, my sister, and our friends to pull up tarry pieces, a fun but extravagantly messy activity, befo
re she had the area seeded.) Year by year, the roots grew farther out into the lawn while simultaneously heaving themselves ever higher out of the soil. It was as if they, like my parents, had plans for getting out of town.
By the time my parents left Baltimore, hardly any grass grew in the front yard. Whatever blades did emerge from the crevasses among the roots couldn’t be cut, unless you were willing to go at them with a pair of scissors. No doubt the state of the yard had something to do with the lack of interest in the property. Most suburban buyers wanted a lawn, not a bas-relief of roots. Luckily for my parents, a single man, a sports photographer who traveled frequently and must have considered a yard that didn’t need mowing to be an asset, made an acceptable offer.
All was going smoothly with the transaction until the home inspection report came in. It seemed that the sewer line was not draining as it should. A plumber was summoned to investigate. He called to tell me that a tiny silver-maple root tip had found an equally tiny crack, slipped through it, and, having stumbled upon a rich supply of water and fertilizer, prospered mightily, becoming “an eight-foot horsetail” of silver maple roots. A pipe invasion of this sort was not an uncommon occurrence, he said, especially where clay pipes and maples, willows, and sweet gums were concerned. He’d once found the roots of a maple had traveled under a street to invade and clog a neighbor’s sewer line fifty feet away.
Naturally, the photographer was not satisfied with a mere snaking of the pipe, and asked for a visual inspection. Right he was: The root that had taken up residence in the pipe had broadened in girth over time, thereby enlarging the original crack into a significant hole. Many hundreds of dollars later, that section of pipe was replaced, and the deal closed.
I now know that the intruder was a “sinker root,” a type of root that drops down from lateral roots in search of water. On encountering the condensation on a clay sewer pipe, sinker roots spread across its damp surface. If a tree is lucky, and the homeowner isn’t, a sinker finds access to the inside of the pipe. Sinker roots, although occasionally a menace to sewer and water pipes, are an important part of the answer to why tall trees manage to stay upright under most circumstances. As trees mature, their taproots often atrophy. While shallow lateral roots generally do little to anchor trees, some laterals grow obliquely downward. Even better, sinkers grow straight down. (I never saw the sweet gum’s sinkers; they are relatively slender and were left in the earth as the tree fell.) Although the trunk and leafy branches of a tree like the sweet gum might weigh five tons, the weight of its oblique laterals and sinkers, together with the vast amount of soil they enclose within their grasp, can weigh many times more. The roots and soil act, in essence, like the bulbous lead keel of a sailboat.
I’d never had any interest in roots, pale and witchy-fingered things that probe and poke the darkness underground. I didn’t like to think about them, and was glad they were usually hidden from sight. But gardeners ought to know that, according to the University of Colorado, about 80 percent of all plant problems are really root problems. The beauty of flowers and the bounty of a harvest have almost everything to do with roots.
seven
The Enormous Gourd
Steve Connolly’s prize-winning pumpkin, which I have come to see at the New York Botanical Garden, is the third-heaviest pumpkin grown in North America this year. It weighs nearly 1,700 pounds. Picture a caramel-colored Smart car lying on its side, and you have its rough dimensions. Steve’s pumpkin has only one door, though. That door, a rectangular, foot-thick section of yellow-orange rind, is sitting on the ground, leaving a hole that is just large enough for a skinny young man to wiggle through. In fact, such a man is inside the pumpkin, and has just poked his torso and dark-haired head out of the hole to place a white plastic bucket on the ground. He is wearing a headlamp and, despite the autumnal chill, a T-shirt. The bucket, the young man tells me, is full of seeds he has scraped from the interior rind. Inside the pumpkin, he further reports, it is very dark, warm—the strong noon sun seems to turn the pumpkin into a solar oven—and wet. Having issued this report, he disappears again into the pumpkin.
If you were to put this pumpkin on wheels and hitch it to a team of white horses, you could ride to the prince’s ball in it. There would be room for your fairy godmother, too. But if you’re going to go dancing, it had better be tonight. Tomorrow is October 29, and an artist will be turning this pumpkin and the first-place winner (1,810.5 pounds from Minnesota) into the world’s largest jack-o’-lanterns.
I am waiting for Steve to arrive, imagining a hefty farmer in denim overalls. Instead, I find myself shaking hands with a slight, pale, bespectacled, and soft-spoken man in his mid-fifties who I discover has a BS in plastics engineering and a job at a large medical company. He is wearing an orange baseball cap and a jacket emblazoned with the emblem—a bright orange pumpkin impressed with a green map of the world—of the Great Pumpkin Commonwealth. The GPC, he explains, is the umbrella organization of some forty regional clubs whose ten thousand members are devoted to “extreme gardening.” Extreme gardening refers to the size of the fruits they grow—tomatoes, squash, long gourds, watermelons, and pumpkins—as well as the fervor they bring to their cultivation. They’re committed to doing whatever it takes to grow the largest garden fruits the world has ever seen. As Don Langevin, author of the pumpkin growers’ bible, How-to-Grow World Class Giant Pumpkins, writes: “From April to September and beyond, a serious giant pumpkin grower must dedicate his or her life to his plants.”
So, what does it take to grow an orange gourd that weighs as much as a small car? You have to start with seeds of the Cucurbita maxima “Atlantic Giant.” This is not the variety you find in late October dotting the fields of pick-your-own farms. You might be able to purchase Atlantic Giant seeds at your local garden center, but you’ll probably raise a pumpkin that weighs a mere several hundred pounds. If you’re going for the gold, you had better contact prize winners of the last few years and see if they’ll sell you a few of theirs. Or, you can try to buy them at auction. “Proven” seeds, those harvested from a prize winner that produced winners in the next season, can set you back many hundreds of dollars. Seeds from the 2010 champion went for $1,200 each.
You’ll also need a good part of an average suburban backyard. Each plant requires a thirty-foot by thirty-foot patch, and it’s wise to cultivate several plants. Your patch should be completely sunlit because your pumpkin is going to need every available photon. The shade of a tree might stand between you and immortality, and more than a few trees have given their lives to the cause. You’d also do well to live in the “orange zone,” which in North America lies between the 40th and 46th parallels, that is, roughly from San Francisco to Vancouver, from Nebraska up to Ontario, and from Pennsylvania through St. John’s, Newfoundland. In this region you will find the greatest number of daylight hours paired with the greatest number of frost-free days.
Even so, Steve warns, you will need to start your seeds indoors under grow lights in mid-April; otherwise you’ll be behind the serious competition by the time the danger of frost has passed. Don Langevin advises that if you’re new to the sport, you ought to start practicing germinating seeds in early March, in order to build your confidence for when G-day arrives. About May 1, it’s time to transplant your young plants outside. Competitive growers build a plastic greenhouse the size of a small doghouse over each one. These can get elaborate, with buried heating cables to raise soil temperature to the ideal 85 degrees. When your vines outgrow their enclosures, you might want to build a windbreak of straw bales close by so they won’t get twisted or otherwise damaged.
Left to their own devices, your plants’ vines will branch and rebranch and then rebranch some more, crisscrossing each other while growing several inches a day into a wrist-thick spaghetti of vinery. The plants will also want to develop lots of leaves, which are as big as serving platters and hover above the vines on two-foot-tall stems. Your vines will also want to produce many small (relatively speaking
) fruits that can hide under those leaves. In this way, even if insects and deer graze the leaves and raccoons or groundhogs discover most of the fruits, the likelihood is that one pumpkin will survive to autumn to produce seeds for the next generation.
You, on the other hand, want all the plant’s energy going to develop one monster pumpkin, and you want only as many leaves as are needed to supply the energy for that one fruit’s growth. As growers often told me, you are not trying to grow a salad, you are trying to grow a pumpkin. A rampant tangle of vines and leaves means some leaves will shade others, and shaded leaves are slacker leaves when it comes to the business of gathering sunlight. So it’s your job to go into the patch every day and prune, arrange, and stake, the rapidly growing vines so that they conform to your ideal. You want the vines to grow in a pattern that looks, spread out on the ground, like the profile of a Christmas tree. If you had an aerial view, your pumpkin would look like a humongous orange ornament smack in the middle of that tree.
In early June, it is time for you to pollinate the bright yellow female flowers. Pumpkins have separate male and female flowers growing on one plant. It won’t matter to the success of this season’s fruit which male flower pollinates your female flowers—your pumpkin’s genetics were encoded in the seed you planted. But, if your plumpening darling turns out to be a winner, the value of her seeds will be a function of the seeds’ parentage. So, many growers cap their emergent female flowers with a plastic cup or a sock—a sort of pumpkin condom—so that some randy flower on some loser vine won’t knock up their pedigreed virgins. When the moment is right, you will brush the females’ pistils with pollen either from your male flowers (a process called “selfing”) or with the pollen from another grower’s pedigreed plant.
A Garden of Marvels Page 7
