Reynoutria japonica

Common Name: Japanese knotweed

Family: Polygonaceae

Common Synonyms: Polygonum cuspidatum

USDA Hardiness Zone: 4a - 8b

Growth Habit: Shrub

Origin: Eastern Asia

FISC Category: -

FDACS Listed Noxious Weed: No

Introduction Date: Introduced in US late 1800's, not established in Florida

IFAS Assessment:

• North: Not Assessed
• Central: Not Assessed
• South: Not Assessed

Description

Perennial shrub with glabrous stems (mostly not branched) that ascend from a rhizomatous base, to 3 m tall, often forming a dense infestation. Stems reddish, hollow, swollen at nodes, and tend to zigzag slightly from node to node. Alternate leaves are oval-shaped 7-14 cm long and 5-12 cm wide with an entire margin. Axillary panicles with many 5-petaled, tiny, white flowers. Fruits shiny, brown, triangular nuts.

Habitat

River banks, wetlands, disturbed areas, railways, prefers open sunny habitats

Comments

No specimens from FL, closest in central GA. Present in most northern states and Canada. Climate could prevent naturalization in FL but good to monitor. Very fast growth. Predominantly reproduces vegetatively via rhizomes.

Control Methods

• Manual: NA
• Chemical: Foliar (aquatic label glyphosate, Alberternst, and B?hmer) , foliar (1% triclopyr amine mixed with 2% aquatic label glyphosate, Miller et al.), Foliar in aquatic sites (1% isopropylamine salt of Imazapyr mixed with an aquatic surfactant, Miller et al.), cut-stem (50% aquatic label glyphosate, Alberternst, and Bohmer). Fall applications are most effective.
• Biological: NA

Control Notes

**Follow herbicide labels: Only herbicides registered for application in water by EPA and FDACS may be applied to weeds growing in or near water.

References

Alberternst, B. and H.J. Bohmer. 2011. NOBANIS Invasive Alien Species Fact Sheet Fallopia japonica. Online Database of the European Network on Invasive Alien Species NOBANIS www.nobanis.org. Accessed on December 10, 2013.

CABI. 2013. Japanese Knotweed Alliance. http://www.cabi.org/japaneseknotweedalliance/default.aspx?site=139&page=52. Accessed on December 10, 2013.

Dave's Garden. 2013. PlantFiles: Variegated Japanese knotweed, Speckled Mexican bamboo, Fallopia japonica. http://davesgarden.com/guides/pf/go/57523/. Accessed on December 9, 2013.

Miller, J.H., E.B. Chambliss, and N.J. Loewenstein. 2010. A Field Guide for the Identification of Invasive Plants in Southern Forests. U. S. Department of Agriculture, Southern Research Station. Asheville, NC.