Prostrate Knotweed

By Barbara Pleasant, June 23, 2008

Prostrate knotweed (Polygonum aviculare) is one of the first annual weeds to appear in spring. Common throughout most of North America, knotweed stems spiral outward from a central crown, forming mats of blue-green foliage. A thin, light green sheath covers the base of each blue-green leaf, and helps to hide the small white flowers that are wedged into the leaf axils (where leaves are attached to stems). Knotweed exudes chemicals that inhibit the growth of nearby grasses. Apply a corn gluten herbicide in spring to reduce seed germination. Pull older plants rather than mowing over them, which can increase reseeding.

Weed Control Techniques

Corn gluten herbicides. Powdered herbicides made from corn gluten keep crabgrass and other weed seeds from germinating and growing. They are typically spread on established lawns, but they also can be used in gardens where no seeds will be planted, such as in perennial beds. As the corn gluten degrades, it provides a small amount of nitrogen to the soil. Crabgrass begins to germinate at about the time that azaleas, dogwoods, and forsythias bloom, so spread corn gluten at that time for best results. Application procedures vary with the particular product; be sure to read and follow the directions on the label. Do not use corn gluten in newly seeded lawns, or in garden beds where you plan to sow seeds.

Pulling. Most young weeds can be pulled from the soil. They will slide out most easily if you pull them when the soil is wet. Getting the root up is crucial, so think of the main stem as the root's handle, and grasp it as close to the soil line as you can. If you find that the weeds are breaking off at the crown as you pull, slip a kitchen fork, dandelion weeder, or similar tool under the weed, and pry and twist as you pull it up. Weeds that have taproots, such as dandelion and plantain, usually must be pried out. A flexible pair of waterproof gloves will keep your hands comfortable as you weed, and it's good to have a nice sitting pad, too. Let pulled weeds bake in the sun for a day or so before composting them. If pulled weeds are holding mature seeds, compost them separately in a hot, moist pile before using this compost in the garden.

Photo courtesy of Randall G. Prostak, University of Massachusetts

Other Broadleaf Weeds
Black Medic
Weed info for Black Medic
Broadleaf Plantain
Weed info for Broadleaf Plantain
Buckhorn Plantain
Weed info for Buckhorn Plantain
Buttonweed
Weed info for Buttonweed
Canada Thistle
Weed info for Canada Thistle
Carpetweed
Weed info for Carpetweed
Chickweed
Weed info for Chickweed
Cinquefoil
Weed info for Cinquefoil
Corn Speedwell
Weed info for Corn Speedwell
Curly Dock
Weed info for Curly Dock
Dandelion
Weed info for Dandelion
English Daisy
Weed info for English Daisy
Ground Ivy
Weed info for Ground Ivy
Hawkweed
Weed info for Hawkweed
Henbit
Weed info for Henbit
Hop Clover
Weed info for Hop Clover
Horsetail
Weed info for Horsetail
Indian Mockstrawberry
Weed info for Indian Mockstrawberry
Lambsquarters
Weed info for Lambsquarters
Mallow
Weed info for Mallow
Pigweed
Weed info for Pigweed
Prickly Lettuce
Weed info for Prickly Lettuce
Prostrate Knotweed
Weed info for Prostrate Knotweed
Purslane
Weed info for Purslane
Ragweed
Weed info for Ragweed
Shepherd's Purse
Weed info for Shepherd's Purse
Smartweed
Weed info for Smartweed
Sorrel
Weed info for Sorrel
White Clover
Weed info for White Clover
Wild Garlic
Weed info for Wild Garlic
Wild Violets
Weed info for Wild Violets
Woodsorrel
Weed info for Woodsorrel
Yarrow
Weed info for Yarrow

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