Mulching Your Annual Flowers

Mulching your plants can have many benefits. An essential part of a weed management program is use of an organic or inorganic mulch. A 3- to 4-inch (8 to 10 cm) mulch will suppress weed seed germination and growth, and will provide adequate control of most annual weeds.

Mulches control weeds by depriving them of light. Organic mulches e.g., pine needles, pine bark, hardwood bark, leaf mold (old leaves), etc. or inorganic mulches e.g., gravel, stones, etc., may be used.

Organic mulches must be periodically replenished to maintain the 2- to 4-inch (5 to 10 cm) depth for suppression of weed seed germination. When mulches are too fine, too thick, or begin to decompose, they stay wet between rains, allowing weeds to germinate and grow directly in the mulch. Therefore, for weed control, a mulch which is coarse-textured with a low water-holding capacity is preferred.

In addition, escaped weeds in the bed and weeds in the surrounding areas should not be allowed to produce seeds which can be blown into the flower bed. Mulches are not effective in controlling perennial weeds such as quackgrass, bermudagrass, nutsedge, and mugwort. Mulches must allow free passage of water and air since both are essential for healthy, aesthetic plants.

While black plastic will prevent weed seed germination, it also prohibits free passage of water and air and should not be used. Using mulch and spacing plants so they produce a solid canopy are the best ways to minimize weed problems.

Mulching also helps to retain soil moisture, especially during the hottest parts of the day or an extended time without watering. Be sure to mulch your plants and water well before leaving on that summer vacation.

Another function of mulching is to protect your annual flowers late in the season from the damage of an early frost. Anytime there is a threat of frost, you will want to take precautionary measures to protect tender annuals from exposure to cold temperatures.

If you have advance warning of a particularly heavy frost you will nedd to cover your plants with old blankets, sheets, or burlap bags. Lighter covers may be draped directly over the plant while heavier material will requires some kind of support to avoid crushing your flowers. Be sure to remove any covering as soon as the sun comes out to avoid suffocating your plants.