Japanese Knotweed

Japanese Knotweed5/16/2012

Managing Aquatic Resources Since 1966

Invasive Species Japanese Knotweed Buckwheat family

(Lythraceae) Scientific Name: Fallopia

japonica Previously: Polygonum

cuspidatum Common Names: Japanese

knotweed, fleece flower, Mexican bamboo, huzhang

Distribution Native to Asia Colonized the United States in Late 1800’s Introduced as an ornamental and for erosion control Presently found in a significant portion of North America

Description/Identification Herbaceous shrub 3-12 ft. tall Reddish, hollow, and jointed stems Alternate leaves are 4-6 inches, ovate with pointed tips

and flat bases

Flowers Flowers May to September Flowers terminal and auxiliary Branched sprays (racemes) 3-6 inches long Covered with tiny 5-petaled (sepaled) white to greenish

flowers 3 styles and 8-10 stamens

Fruit August – November Dangling Winged 1 triangular shiny nutlet

Life Cycle Stems and leaves survive one season Rhizomes survive many years Grows fast in spring from rhizomes and seeds Crowds/shades other species Prefers open areas such as riparian corridors, roadways,

etc. Does well in wetlands

Dispersal Mechanisms Ornamental trade Fragmentation Disturbance colonization

Riparian flooding Roadway mowing

Impacts Alters natural ecosystem Crowds out native vegetation Dense stands provide limited wildlife habitat Causes structural damage to buildings, sidewalks, roads

Control Options Education/Prevention Physical Biological

Aphalara itadori

Chemical

Chemical Control Options Renovate 3 as 2% solution Glyphosate

Foliar application with 2% solution Cut-stem application (label details)

Combination of Glyphosate (2%) and Renovate (1%) Habitat as 1% solution Early treatments prevent seed production Late season treatments are more effective on rhizomes

Japanese Knotweed SherbetThis sour rhubarb relative lends its lemony flavor and thickening qualities to this sweet-tasting sherbet.3 cups Japanese knotweed stalks, peeled if desired, coarsely sliced

1-1/3 cups orange juice (freshly squeezed is best)1-1/2 cups apple juice or other fruit juice1/2 cup lemon juice1/4 cup canola oil1/4 cup vegetable glycerin, honey, barley malt, or rice syrup1 tbs. freshly grated (or 1 tsp. dried) orange rind2 tsp. vanilla extract1 tsp. lemon extract1 tsp. liquid stevia (optional)1/4 tsp. salt1.

1. Simmer the Japanese knotweed shoots in the orange juice, apple juice, and lemon juice 10 minutes or until soft.2. Puree in a blender with the remaining ingredients.3. Chill.4. Pour into an ice cream machine and run it until done.

Questions?

Managing Aquatic Resources Since 1966