Everyone knows the old cliche about life’s only certainties: Death and Taxes. For farmers, however, there’s a third. But unlike the other two, this is a certainty that is in your face every day, reminding you who is boss, taunting you with its inevitability.
It’s not an “it”. It’s a “them”. Weeds.
There’s a tendency to think of weeds as part of nature. But if you speak to a real ecologist or environmental scientist, you will find they are probably just as worried about weeds as any farmer. That’s because nature does not make weeds — humans do. To a scientist, a weed is not just a plant growing in a place where you don’t want it growing. It is a plant that has evolved in response to human activity, outcompeting other plants in the process. An article in Tuesday’s New York Times explains very nicely how plant species evolve into being weeds, becoming adapted to difficult environments through natural selection.
Usually the worst weeds in a given place are not even native to the area. Invasive weed species are brought from elsewhere, almost always by human activity. Without natural control — animals and bugs that eat them, diseases that kill them — they spread quickly and overwhelm both native plants and agricultural crops. Yellow Starthistle is a perfect example, a super drought tolerant Australian plant that has taken over millions of acres of land in California formerly dominated by native. grasses.
Weeds are the most costly pest in both conventional and organic agriculture, both in terms of the crop losses they cause and the amount of money spent on controlling them. But organic farmers spend more, and lose more crops — to weeds than conventional ones. That’s because at this time there simply are no effective organic herbicides.
Instead, organic farmers rely on old fashioned methods of weed control. We use tractors with special machinery to weed between the crop rows, and hoeing or hand weeding to weed between the plants. We rotate crops grown during different seasons so as not to allow the same weeds to grow in the field each year. We grow vigorous cover crops that shade out and smother weeds.
Over time, however, the wiliest weeds figure out a way. At Terra Firma, our most important form of weed control is irrigating our fields a week or two before planting to sprout the seeds, and then lightly cultivating the soil to kill them before planting. While this kills an enormous amount of weed seeds every time we do it, it has given preference to plants whose seeds take longer to sprout. Some of the worst weeds on our farm are those that germinate underneath the canopy of a fully grown crop and go to seed just before we harvest the field.
This is just one of the reasons why weeds haunt me awake and asleep. When I walk the fields here, they taunt me, laughing at my efforts to get rid of them. In my dreams I see them taking over our fields.
And so I will end this newsletter with another weed-related twist on a common cliche: You might say I’m paranoid about weeds. But I know better. They are out to get me. They really are.