Some years are better than others for garden vegetables, but I grow one set of abundant crops without fail every year: weeds. They reappear as quickly as I yank them out, like aliens from a horror movie.
 | Science fiction/horror movies have long celebrated killer plants: The Thing from Another World (1951: a resilient plant-based alien); The Day of the Triffids (1962: walking alien plants); Attack of the Killer Tomatoes (1978: sentient tomatoes rebel against humanity); Little Shop of Horrors (1986: an alien plant with a taste for human blood); The Happening (2008: trees defend themselves agaisnt humans with psychosis-inducing pollen). |
Actual weeds are as fantastical as anything in fiction. For example, in Weeds: In Defense of Nature’s Most Unloved Plants, by Richard Mabey, the author says, “In a single summer each underground stem [of ground elder] can extend as much as three feet, so that from a single rosette an area of more than a yard square has been colonized. The roots plunge down as well, to unprecedented depths. In a quarry in Kent…a worker found ground elder roots probing thirty feet below the surface. …[and] almost any fragment of the wiry root system or shoot, cut up by hoe or spade, can generate a new plant.”
 | Another fabulous weed Mabey describes is knotweed. “Each [knotweed] had a root system that could extend six feet underground and advance the growing shoots of the plant twenty feet or more each year. …The spring shoots, several of which appear from the bulky rhizome, can break through asphalt, lift concrete slabs into the air, and reach a height of five feet in four weeks.” |
How do weeds become so voracious? According to Mabey, we create them:
First, it’s important to realize that weeds are naturally resilient~
“Weeds’ rapid, opportunist lifestyles mean that their role—what they do—is to fill empty spaces of the earth, to repair the vegetation shattered naturally for millions of years by landslide and flood and forest fire, and today degraded by aggressive farming and gross pollution. In so doing, they stabilize the soil, conserve water loss, provide shelter for other plants, and begin the process of succession.”
“Weeds’ rapid, opportunist lifestyles mean that their role—what they do—is to fill empty spaces of the earth, to repair the vegetation shattered naturally for millions of years by landslide and flood and forest fire, and today degraded by aggressive farming and gross pollution. In so doing, they stabilize the soil, conserve water loss, provide shelter for other plants, and begin the process of succession.”
Second, this adaptability is genetically enhanced~
“It’s long been known that many plants —e.g., juniper or fat hen—can exist in different forms in different habitats without any genetic variation between types. It now looks as if these “epigenetic” effects can be produced in individual plants within a very few seasons or generations. ... gene complexes shared by many weed species, which predispose them, for example, to fast growth and adaptability.”
“It’s long been known that many plants —e.g., juniper or fat hen—can exist in different forms in different habitats without any genetic variation between types. It now looks as if these “epigenetic” effects can be produced in individual plants within a very few seasons or generations. ... gene complexes shared by many weed species, which predispose them, for example, to fast growth and adaptability.”
Third, agriculture promotes the evolution of modern weeds~
“…just as the hoe gave advantage to individual weed plants with deep roots that could regenerate when chopped, and grain sieves helped the evolution of weeds whose seeds were the same size as crop grains, so chemical weed killers actively encouraged the evolution of individual weeds whose biochemistry is unusual enough to be immune to the poison.”
This “endless game of chemical poker” encourages increasingly resilient weeds. Over fifty species “have evolved some type of resistance to a wide range of herbicides.”
“…just as the hoe gave advantage to individual weed plants with deep roots that could regenerate when chopped, and grain sieves helped the evolution of weeds whose seeds were the same size as crop grains, so chemical weed killers actively encouraged the evolution of individual weeds whose biochemistry is unusual enough to be immune to the poison.”
This “endless game of chemical poker” encourages increasingly resilient weeds. Over fifty species “have evolved some type of resistance to a wide range of herbicides.”
 | Weeds not only inspire fantastical stories, they also provide a mirror: “Every single weed nuisance—from the ground elder in the over-hoed English herbaceous border to the casually imported pond plant suffocating the Everglades swamps, to the cogon smothering the napalmed remnants of the Vietnamese rainforest—has been the consequence of thoughtlessness and sometimes deliberate disruption of natural systems. Weeds are our most successful cultivated crop.” “[Weeds] are mobile, prolific, and…use multiple strategies for getting their own way. …the species they most resemble is us.” |
For more on fascinating plant facts, read Serving Plants and Plant-Animal Hybrids.
RSS Feed