University of Connecticut University of UC Title Fallback Connecticut

Japanese knotweed (Polygonum cuspidatum)

Japanese knotweed is an herbaceous perennial which forms dense clumps 1-3 meters (3-10 feet) high. Its broad leaves are somewhat triangular and pointed at the tip. Clusters of tiny greenish-white flowers are borne in leaf axils during August and September. The fruit is a small, brown triangular achene. Knotweed reproduces via seed and by vegetative growth through stout, aggressive rhizomes. It spreads rapidly to form dense thickets that can alter natural ecosystems or interfere with landscaping. Japanese knotweed can tolerate a variety of adverse conditions including full shade, high temperatures, high salinity, and drought. It is found near water sources, in low-lying areas, waste places, and utility rights of way. It poses a significant threat to riparian areas, where it can survive severe floods. (Source: EDDMapS)
Management Options:

A. Hand Pulling

B. Cutting & Mowing

C. Propane Torch

D. Herbicides

E.Grazing

A. Hand Pulling
Control can often be accomplished by hand-pulling for small populations (less than 1/4 acre). Plants pulled early in the season are much smaller and easier to manage.

B. Cutting & Mowing
Mowing (or brush hogging where woody plants are present) is suited to non-rocky, open areas that are not too steep for the equipment. Obviously, mowing affects all plants mowed, not just the target species. Equipment should be cleaned prior to being brought to the site and should be thoroughly cleaned of all seeds and plant parts before leaving the site.

C. Propane Torch
Backpack-mounted propane torches can be used for invasive plant control.  This method uses targeted fire to heat the base of a plant, killing it.  Some plants with developed roots may resprout after this treatment.  Safety training is needed before using this method.

D. Herbicides
Herbicides are pesticides used for vegetation management. Herbicides can be a valuable tool in controlling invasive species, but they must be used with caution.
Always read the entire herbicide label and apply herbicides according to label directions. Wear the personal protective equipment specified on the product label and heed any and all environmental restrictions stated on the label.
Most herbicide products, especially those marketed to homeowners and small property owners, are classified as “General Use” pesticides. Only licensed pesticide applicators are allowed to purchase or apply “Restricted Use” pesticides.

E. Grazing
Grazing means using animals to eat plants.