Gardeners often consider weeds the most difficult part of maintaining a vegetable garden. A select few weed killers that will not kill vegetable plants are available on the market although you should still use care when applying them. This is especially important if you grow a variety of vegetables in one garden as some weed killers will ruin certain vegetable plants while having little effect on others.
Pre-emergent Herbicides vs. Post-emergent Herbicides
Pre-emergent herbicides prevent weeds from growing in the first place, rather than killing existing weeds. Gardeners can apply this herbicide to their gardens in the fall after harvest or in the early spring, before planting, to prevent the development of certain weeds throughout the growing season. Some pre-emergent weed killers are relatively safe to use once the vegetable plants are in the ground. Post-emergent herbicides, on the other hand, kill existing weeds although they typically do not prevent new weeds from growing. Gardeners can use these to clear up an overrun vegetable garden in the fall after harvest or carefully spray it in between vegetable plants during the growing season.
A pre-emergent herbicide, dacthal is available under several different brand names. This chemical primarily controls the growth of grass in vegetable gardens, which often occurs when you dig out a plot in the middle of a lawn. Dacthal is also relatively effective at controlling dandelions and plantago.
Also a pre-emergent herbicide, trifluralin should only be applied prior to sowing seeds or transplanting vegetable starters. Mix in granules of this weed killer with the top 2 inches of soil, making sure you evenly till the soil to prevent clumping. Trifluralin is most effective for preventing the growth of grass in vegetable gardens, especially bluegrass and crabgrass.
If you have a problem with annual grasses growing in your vegetable garden, the post-emergent herbicide poast may be an option. This weed killer works best when applied early in the season before vegetable plants reach a height of 6 to 8 inches. One application can typically control the growth of annual grass for the entire growing season, as well as alfalfa and clover. If you are looking to kill perennial grass in your vegetable garden, you need to perform several applications throughout the season, taking care to keep it away from your plants. This weed killer can be harmful to certain crops, including carrots, bean sprouts, okra and several types of greens although it is safe for most others.
Another post-emergent weed killer, glyphosate can control a variety of weeds. It is also safe for use after seedlings have emerged or you have transplanted a variety of traditional vegetable seedlings. Certain crops experience little to no damage from glyphosate, including soybeans and corn.