Prostrate Knotweed

Prostrate knotweed (Polygonum aviculare) is a summer annual. This plant grows in many areas such as lawns, landscape plantings, and unmanaged sites. It specializes in stressed areas, favoring compacted soil and low nutrients, which are sites that most plants do not want to inhabit. Reproduction is via seeds that germinate very early in the spring. The plant develops slowly, but is easily noticeable by mid-summer. Most of a knotweed's growth is lateral and not vertical.

Mature plants form mats of slender stems. The stems are swollen at the nodes. The leaves are lance-shaped and have an ocrea (membranous sheath) at the base. The flowers are very small and not noticeable. In general appearance, knotweed can be confused with spotted spurge or purslane. However, spurge has opposite, not alternate leaves; the leaves of the young spurge in particular have a red spot on each leaf; and the sap of spurge is milky and sticky. Purslane differs from knotweed in that the stems and leaves are fleshy (succulent), reddish at the base, and the foliage lacks an ocrea.

In small numbers, hand weeding can be done. Knotweed has a small tap root.

Numerous Herbicides are Labeled for Preemergent Use

• Barricade (prodiamine)
• Devrinol (napropamide)
• Dimension (dithiopyr)
• Goal 2XL (oxyfluorfen)
• Pendulum (pendimethalin)
• Surflan (oryzalin) to name a few

Post-emergent Herbicides Include

• Goal 2XL (oxyfluorfen)
• Lontrel (clopyralid)
• Roundup and other products (glyphosate, non-selective)

Remember to read the label for proper application sites and rates.

Mulch can also be used whenever possible as a non-chemical management option, along with alleviating soil compaction.