Weed Control

When I give farm tours people often seem surprised when I say that organic farmers are at more of a disadvantage, compared to their conventional counterparts, in the area of weed control versus pest and disease pressure. Conventional growers commonly use pre-emergence herbicides at planting time that prevent weeds from germinating in the strip of soil where their crop seeds are sown. Selective, post-emergence herbicides, which kill most of the surrounding weeds but leave the crops unscathed, are also used for many crops. Conventional strawberry growers in our area fumigate at planting time with materials that kill most of the weed seeds in the soil.

Needless to say, those are all options that aren’t available to organic growers. When it comes to weed control, we have to be creative and resourceful—using a variety of methods to ensure our crops are not out-competed. One of the organic mainstays is the use of transplants—plants that are reared in trays in the greenhouse as opposed to sown directly in the field. When planted out in the field, transplants have a significant head start on the weeds, but this alone doesn’t guarantee success. Within 10-14 days after transplanting, we make a pass with our cultivating tractor which uses knives to undercut the weeds to within an inch or two on either side of our crop “seed-line.” This, of course, does not kill the weeds in between the plants in the seed-line, which is why we still have to make a pass using stirrup hoes to clean up this space.

This system has worked well for us, but the problem is that not all crops grow well from starts and with others it just doesn’t make sense—high density crops like cilantro, radishes, arugula and beets would take forever to plant out and be totally uneconomical. For these direct seeded crops we use another method of weed control called the “stale seedbed” technique. This is when we get our beds completely ready, and then irrigate thoroughly. We will typically irrigate a second time and then wait for all of the weeds to come up. After 10-14 days we make a pass with our propane “flamer.” This is an implement that has four burners arranged to kill all of the weeds across the entire bed top. The advantage of using this technique, versus mechanical cultivation, is that it leaves the soil undisturbed and doesn’t dredge up more weed seeds from deeper down to germinate.

Using these techniques we are able to get a healthy crop off most of the time. It certainly doesn’t mean that we have a weed-free farm—far from it. Although things can look a little too ragged around here at times for my liking, it’s far better than the alternative. When I drive past the barren conventional fields around here and see them dousing their ditch banks with herbicide—the same ditches where I often see mating pairs of mallards and great blue herons—it makes me sad. And here on our farm when I see song birds flitting along, eating the seeds off of sowthistle plants that we have neglected to hoe out, it always brings a smile to my face.