Q: We want to start a vegetable garden on a plot of land that has not been mowed for a couple of years. The weeds have grown pretty tall, but they have been mowed this year in preparation for the garden. What can we use to kill the weeds that would still allow us to possibly apply for an organic certification in the future?
There are several techniques that you can use to kill the stuff growing now, but you will also have to deal with a large supply of weed seeds that will come up this year and for several years to come.
If there is still a lot of brown stems and debris left from the previous weeds, you might be able to burn the area, which will also kill some of the weed seeds. It may be too late in the year to do this one.
Both black and clear plastic sheets have been used to kill plants. Black plastic or rubber sheeting will heat up the plants and soil, which kills plants. And if it is hot enough, it can even sterilize the soil a few inches deep. Clear plastic will act like a greenhouse and cook the plants, but it doesn't get hot enough to heat the soil. After a week, check under the plastic to see how the plants are doing.
Any opaque material, such as old carpeting, can be used on small areas. Just leave it a week or two and the plants underneath should be dead. Nearly dead plants will be finished off when they are tilled up.
Plowing the area several times a few days apart will destroy most plants, but it's labor intensive. Hand pulling and digging are, of course, even more labor intensive.
There are a few weed-killing chemicals used by organic growers. You will have some weeds that are grasses and some that are called broad-leaved weeds. Having both kinds of plants will mean using a total plant killer.
Highly concentrated vinegar is the active ingredient of a product called BurnOut II. Normal household vinegar may kill some plants, but it is not concentrated enough to do a whole weed patch — boiling the water out of it to make it more concentrated is not something I recommend doing.
A combination of acetic acid and citric acid are the ingredients in AllDown herbicide, making it an herbicide with very little chance of remaining in the soil.
There are several non-selective contact herbicides with a fatty acid base. Generally, these products are known as herbicidal soaps. One of the brand names is Weed-Aside.
If you will be planting all your garden plants as transplants and not from seeds, you can use a pre-emergent herbicide to stop the weed seeds from sprouting. This product will prevent garden vegetable seeds from growing, too.
I would cover the whole garden with a weed barrier cloth or several inches of mulch to prevent seeds from growing. The cloth will let seeds sprout and the weeds may even grow, but if they are under the cloth, you won't have to deal with them. Plus, the vegetables will be cleaner growing on the cloth rather than the soil.
The main thing is just keeping after the weeds. Nothing will work perfectly, so when they come back up, you need to hit them again. After several hits, you win. If they are only hit once, they win.
E-mail questions to Jeff Rugg, University of Illinois Extension at jrugg@illinois.edu. To find out more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.
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