Polygonum or Common Knotgrass

Description

• Knotgrass grows in the summer, naturally appearing in turfgrass. In its early stages, knotgrass is almost indistinguishable from the surrounding turfrass. As a medicinal herb, knotgrass displays astringent properties and helps to stop bleeding when taken internally. Externally, knotgrass may be used to treat skin ailments. Knotgrass grows 4 to 8 inches high with thin stalks that bear pink and white flowers.

Life Cycle

• Common knotgrass flowers in the summer and autumn, and dies down to the ground in the late fall and winter. Knotgrass may be grown as a perennial or an annual. If left undisturbed, the plant will reseed itself and return the following summer. Common knotgrass is hardy in USDA Zone 3 to Zone 9, and may be grown throughout North America. Knotgrass survives temperatures as low as minus 40 degrees Fahrenheit in winter dormancy.

Cultivation

• Plant knotgrass after the last spring frost date, once daytime temperatures have reached 70 degrees Fahrenheit. Space seeds 8 to 50 inches apart, and cover them lightly with soil. The seeds will germinate in three to eight weeks. Plant common knotgrass in partial shade in well-drained soil. Optimally, the soil pH should be between 6 and 7. With proper cultivation and care, knotgrass will thrive in a garden environment.

Care

• Keep common knotgrass soil moist. Water the soil frequently to keep it from drying out. Prune knotgrass in the spring to prevent leggy, spindly growth that makes the plant look unattractive. In the fall, cut knotgrass back to the ground. Common knotgrass should also be divided in the fall or spring, or it will spread and potentially become invasive. To divide the plant, dig it up and cut through the rhizome. The rhizome is the thick, underground central stem of the plant. Cut the knotgrass plant into approximately three sections and replant it.