One of the most challenging problems in home landscapes is controlling weeds in ornamental beds. We normally think about weed control in the spring and summer, but fall and winter weed control is just as important.
Weeds compete for water, nutrients, light and space, and they can harbor many insect pests. But the main problem with weeds is they spoil the appearance of the landscape.
Keys to proper weed control in landscapes are weed identification, ornamental plant identification and cultural control. Determine whether the weeds are grasses, broadleaves or sedges. Control varies from one to the other. Also it's important to know whether the weed is an annual, biennial or perennial. Be sure you know the names of all ornamental plants in your beds. This is critical in determining what weed control measures you can use. Select a weed-control product that will be effective in controlling the weed species without harming the landscape plants.
An optimum weed-control program uses all available recommended cultural practices. Prevention, manual control, mulching and competition will reduce weed pressure.
Prevention means to make sure beds are weed-free before planting. Remove existing weeds. Many think that tilling will take care of existing weed problems, but tilling actually can bring many weed seed to the soil surface where rapid germination will occur once conditions are favorable. Mulching after tilling, retilling lightly a week or two after the initial tilling and using pre-emergent herbicides are recommended control options.
Most of us don't like it, but hand pulling weeds can accomplish a considerable amount of control. Stay ahead of the weeds. Don't let the weeds stay ahead of you. Be sure to pull any weeds before seed development. Some produce more than 100,000 viable seeds per plant.
Mulching is a great way to control weed problems. Mulch bedding plants to a depth of 1 inch, shrubs to a depth of 2 inches and trees to 4 inches. Don't pile mulch around the trunks of plants. This leads to moisture accumulation and possible disease problems. Pine straw is one of the best mulches to use -- it does a great job on weed suppression.
Vigorous ornamental plants are good competition for weeds. Make sure landscape plants are properly maintained. A solid canopy of foliage from ornamentals will inhibit and out-compete weeds for water, light and space.
Herbicides are an important and sometimes-necessary portion of a weed control program. Herbicides are available that will eliminate grassy weeds from flower beds without damage to the desirable landscape plants. Control of broadleaves and sedges in landscape beds is a more difficult challenge. Pre-emergent herbicides, such as Preen and Amaze, provide good prevention but must be applied at the correct time and rate. Sedges can be controlled after they emerge with several products (example Image), but these products offer limited use around ornamental plants. Be sure to follow all label directions when using these products.