In addition to being unsightly, weeds compete with flowers for light, water, and nutrients. The first—and most important—step in preventing weeds is to remove them before they make seeds. Weeds are prodigious producers of seeds; a stalk of oatgrass may make 250 seeds, and the seed count on a pigweed plant can run into the millions. Most of the weeds in a garden come from seeds that formed there; only a small fraction come from outside. By removing weeds before they produce seeds, you’ll be reducing future weed problems.
The methods you choose to weed your garden depend on whether the weeds are annuals or perennials. Annual weeds can be removed by hoe or by hand, or with an herbicide.
Most annuals can be pulled by hand or cut out with a hoe. When pulling weeds around flowers, be careful not to disrupt the roots of the desirable plants. If a weed is very close to a flower, pinch or cut off the top of the weed at soil level.
Annual weeds can also be killed with an herbicide, such as Roundup. Roundup kills any plants it contacts, so use it carefully if the plants are crowded. Use low pump pressure and keep the nozzle close to the weed. One method is to make a shield from a cardboard box. Place the shield between the weeds and any flowers you want to protect before spraying.
Perennial weeds such as bermudagrass, plantain, and dandelion are tenacious pests that are difficult to remove by hand. Any underground parts left in the soil can resprout and take over the bed in a single season.
You can dig out perennial weeds in the early spring when the soil is moist and the weeds don’t have much top growth. Later in the season, kill the weeds with Roundup. Use the same precautions as with annual weeds.
Perennial weeds can be killed any time they are growing, but fall is the best time for particularly difficult weeds. Weeds with deep root systems, such as bindweed, bermudagrass and witch grass, transport sugars to their roots for the winter just before becoming dormant. During this period, Roundup will be carried most effectively to the far reaches of the root system to kill the entire plant.
Once the weeds are gone, you can prevent new ones from growing by keeping the ground covered with plants and mulch so that the weeds don’t have light. Flowers should be planted close together enough so that, when mature, they form a continuous canopy over the soil. Mulches are particularly effective in the battle against weeds. A 3-inch layer of mulch on the soil will keep most weed seeds from sprouting. (For more about mulches, see About Mulching.)
Weeds can also be prevented with preemergence herbicides, such as garden weed preventer. Weed preventer doesn’t affect growing plants, but kills seeds as they germinate. After applying the weed preventer, don’t disturb the soil any more than necessary. Weed preventer binds with the top inch or so of soil to make a zone where weed seeds can’t germinate. If you mix this top inch into the soil, the weed preventer is diluted too much to be effective.
Despite these preventative measures, some weeds will persistently make their way into the garden. To stay ahead of them, you need to match their persistence by removing young weeds as soon as they appear. Weeds grow so quickly that, if left undisturbed, a few small ones can rapidly turn into a major project. Try to get in the habit of picking a few weeds every time you walk through the garden. The sooner you attend to them, the easier they are to remove and the less chance they’ll have of producing seeds—and the sooner you will have a weed-free garden.