Japanese knotweed
Family
PolygonaceaeScientific Name
Polygonum cuspidatum
Other Common Names:
Japanese bamboo
Synonyms (former Scientific Names):
Reynoutria japonica
var. compactum
Pleuropterus zuccarinii
Pleuropterus cuspidatus
Fallopia japonica
Polygonum cuspidatum
Polygonum zuccarinii
Habit
This erect perennial can grow up to 13 feet in height. It spreads through seeding, and rhizomes.
Leaves
The egg shaped, alternate leaves grow from 4-6 inches in length, and 2-4 inches in width.
Identifying Characteristics
The stems are smooth and swollen at the joints where the leaves grow. The stem above each joint has a thin membranous sheath (ocrea).
Flower Seed Head
Small white flowers grow in clusters from the leaf axils.
Seed Fruit
The seeds are triangular and shiny, and form inside a nutlet.
Where Found
This plant can be found inhabiting areas around streams and rivers. Sunlight, full shade, high salt contents, or drought does not affect this plant.
Growth Habit
upright and nonwoody
Thorns or Spines
not present
Approximate Flower Diameter
Varies:
pencil,
dime
Dominant Flower Color
white
Flower Symmetry
radial symmetery
Leaf Hairs
no hairs
Leaf Shape
oval
Leaf Arrangement
alternate
Leaf Margin
entire
Leaf Structure
simple
Leaf Stalk
shorter than leaf
Stem Hairs
no hairs
Stem Cross Section
round or oval
Milky Sap
not present
Root Structure
rhizomes present
Life Cycle
perennial
Ochrea
present
Plant Type
Shrub