URBANA — As gardeners know, weeds grow almost anywhere. Plants can even survive cracks in the pavement if soil, water and light are present.
Whether a plant is considered a weed depends on how it affects the intended use of the site and who is looking at it.
“A white oak seedling is not normally considered a weed, but when it grows in a vegetable garden it is often treated as such,” says Sarah Vogel, a horticulture educator at the University of Illinois Extension. “Some gardeners remove foliage leaves to create a perfectly manicured lawn, but if you’re a hungry pollinator insect, dandelion, violet, or clover flowers can be a welcome sight.”
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Weeds compete with desirable species for available moisture and nutrients. They can harbor pests and diseases or even pose health hazards. Occasionally weeds are so troublesome that their removal is mandated by the Illinois Noxious Weeds Act. Traits that make weeds so successful also make them difficult to control, and gardeners should consider a management strategy to keep weeds in check.
Because weeds reproduce in a variety of ways, they need to be controlled at different times during the growing season. The most successful approach is a combination of control methods and the right timing. To minimize costs and environmental impact, use mechanical or cultural weed control techniques before trying pesticides.
The first line of defense against weeds is to keep desirable plants healthy. Choose disease-resistant cultivars of species adapted to the site where they will be planted. “Put the right plant in the right spot, check regularly for pests and diseases, provide adequate water and fertilizer, and cover bare soil to prevent weeds,” says Vogel.
A healthy, dense lawn is the best way to keep foliage away. On established lawns, mow the lawn up before the weeds bloom. Lawns mowed at a higher deck height have deeper roots and fewer weeds.
In landscape or vegetable beds, apply mulch to suppress weeds, prevent soil temperature fluctuations, retain moisture, and return organic matter to the soil. Organic sources of mulch include wood chips, shredded bark, straw, grass clippings, shredded leaves, or compost. Inorganic options include landscape fabric, perforated black plastic, or clear plastic that creates a heating effect called solarization.
A mechanical approach to weed suppression is best achieved when the weeds are small. Tillage, hoeing, shoveling, using a flame hoe, or simply hand weeding are efficient but may be impractical for large plots. Some perennial weeds may require repeated treatment.
Cover crops are another way to control weeds in both new and established areas. Some species are chosen for their ability to replenish soil nutrients, while others improve soil crumbling or its physical condition. Cover crops keep weeds at bay by creating a living mulch as they grow densely. When the garden bed is ready for use, some cover crops can be turned under and used as green manure.
Chemical control may not be necessary to treat weeds, and most herbicides are not recommended for vegetable gardens. How effective a product is depends on the type of herbicide used, timing of application, coverage and environmental conditions. Applying unnecessary herbicides can harm crops, soil, water, beneficial insects like pollinators, or humans. Always read and follow label directions when using pesticides.
When starting a new garden plot, manage weeds before planting or you may end up fighting the whole growing season in a losing battle. If weed pressure is becoming too much in your garden beds, you can consider alternative growing systems such as raised beds or containers. Whichever method you choose, weed control will keep your garden healthier and more attractive.
For more information on weed control options, contact your local Illinois Extension County Office at go.illinois.edu/ExtensionOffice.
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