It’s a well-known fact that weeds are unsightly, troublesome plants.
On lawns, they disrupt the lush, green carpet effect we’re trying to achieve. Even worse are the weeds that invade vegetable gardens, where they reduce yield and produce quality.
Weeds compete for available moisture, nutrients, sunlight and acreage. They also serve as shelters for insects, alternative hosts for disease, and hiding places for rodents and snakes.
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Weed control is an important step in maintaining a productive vegetable garden. There are several ways to keep weeds under control.
Be careful with soil amendments. Although manure is a good source of fertilizer, it also contains weed seeds. Compost manure before applying it to your garden plot. Plant plants at the correct depth in soil that has been tested and limed appropriately. Vegetables that get a healthy start in good soil can often suppress weeds with rapid growth and heavy vegetation shading the ground. Vegetables that are good at suppressing weeds through shading include beans, squash, tomatoes, potatoes, squashes, sweetcorn, and cucumbers.
Avoid watering the entire garden which encourages excessive weed growth. Try drip irrigation to place water directly on the plant. Chopping and plucking weeds or cultivating with a rotary tiller is labor intensive but very effective in controlling weeds. Weeds should be removed when they are less than three inches tall and as often as every two weeks. Avoid deep cultivation after the garden has been established as this will attract new weed seeds to the surface and potentially damage the vegetable roots.
Mulching can prevent weeds from sprouting. You can choose between organic and inorganic mulches. Both are equally effective, but inorganic mulches must be removed from the garden each season, while organic mulches can be left or incorporated into the soil. Commonly used organic mulches include bark chips, rotted sawdust, compost, newspaper (shredded or layered), and straw. They should be applied three to four inches deep around the base of vegetable plants.
Organic mulches should be applied in May or June after the ground has warmed up. Plastic is the most commonly used inorganic mulch. Black plastic can be laid in spring to increase soil temperature and therefore planting time. Fertilizer should be incorporated into the soil prior to laying the sheeting.
After it’s been in place for about a week, transplant vegetables into holes cut in the plastic at recommended locations. Clear plastic can be used in summer. When placed on the ground in hot temperatures, it acts as a greenhouse and encourages the emergence of weed seeds. Weeds trapped under the plastic die quickly from the heat. In some cases, temperatures can get high enough to kill many ungerminated weed seeds in the top two inches of soil.
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A fabric mulch is very effective in preventing annual weeds and could be applied in spring. It allows air and water to pass into the soil but prevents weed seedlings from taking root. The cost of cloth mulch in gardens is often prohibitive.
Before crops are planted a non-selective herbicide such as Round-up can be applied to kill existing weeds (autumn, late winter or spring). Round-up should not be used when vegetables are present as damage may occur. Trifluralin (Treflan) can be used as a pre-emergence herbicide to control weed seedlings in gardens. This product is available in granular or liquid form, but is not safe for all vegetables. Read the label before use.
Emerged grasses that are less than four inches tall can be controlled with a post-emergence herbicide containing sethoxydim (poast). As with Treflan, this product is not safe for all vegetables and you should consult the label.
The combination of cultivation techniques, mulching and herbicides will help vegetable crops perform better and increase yields, but perhaps the most important benefit is that it reduces the time you have to spend weeding your garden this year.
Fr. Andrew Rideout is the University of Kentucky Horticultural Extension Agent in the Henderson County Extension Office. You can email him at pandrewrideout@uky.edu.