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Polygonum sachalinense

Polygonum sachalinense F. Schmidt ex Maxim.

Fallopia sachalinensis (F. Schmidt ex Maxim.) Ronse Decr.

Reynoutria sachalinensis (F. Schmidt ex Maxim.) Nakai

Giant Knotweed, Sakhalin Knotweed, Japanese Bamboo

KingdomPlantaePlants, but not fungi, lichens, or algae
SubkingdomTracheobiontaVascular plants—plants with a “circulatory system” for delivering water and nutrients
DivisionMagnoliophytaFlowering plants, also known as angiosperms
ClassMagnoliopsidaDicotyledons—plants with two initial seed leaves
SubclassCaryophyllidaeCacti, many other succulents, carnivorous plants, and leadworts
OrderCaryophyllalesIncludes cacti, carnations, amaranths, ice plants, and many carnivorous plants
FamilyPolygonaceaeKnotweed or smartweed family
GenusPolygonumGreek poly, “many,” and gonu, “knee,” for the swollen jointed stems
SpeciessachalinenseFrom the Sakhalin Islands north of Japan

About plant names...

Giant knotweed is related to the more common and smaller Japanese knotweed. It is Asian in origin, introduced to North America as an ornamental plant. Both knotweeds spread rapidly, and are considered invasive species.

Identification: Giant knotweed favors rivers, swamps, and other wetland regions. They spread via their root systems, which may extend 50 feet or more and have roots up to 3" (7.6 cm) in diameter. Stems are hollow, and thickly clustered, closely resembling bamboo. Plants reach 13' (4 m) in height. Leaves are alternate, ovate (oval, wider at the bottom), cordate (heart-shaped), up to 12" (30 cm) long, with crenate (wavy) edges. Flowers are groups of slender cone-shaped panicles, white or greenish in color, appearing from July to October.

 

Polygonum sachalinense (Giant Knotweed, Sakhalin Knotweed, Japanese Bamboo)

7/17/2010 · Mackworth Island, Falmouth, ME
≈ 16 × 24" (41 × 62 cm)

Polygonum sachalinense (Giant Knotweed, Sakhalin Knotweed, Japanese Bamboo)

These plants are about 10' high. · 7/17/2010 · Mackworth Island, Falmouth, ME
≈ 3½ × 2½' (1.2 × 0.8 m)

Here is a comparison between giant knotweed and Japanese knotweed:

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Polygonum sachalinense

Polygonum cuspidatum
Common Name

Giant Knotweed

Japanese Knotweed
Plant Stems are hollow, and thickly clustered, closely resembling bamboo. Plants are large, up to 13' (4 m) in height. Japanese knotweed stems are jointed and hollow like bamboo. Plants reach up to 12' (3.7 m), but are usually half that.
Flowers Groups of slender cone-shaped panicles, white or greenish in color. In multiple upward pointing spikes containing many tiny white to pale yellow flowers.
Leaves Alternate, ovate (oval, wider at the bottom), cordate (heart-shaped), up to 12" (30 cm) long, with crenate (wavy) edges. Leaves are oval, wider and flat near the base, 2-6" (5-15 cm) long and 1-4" (2.5-10 cm) wide.
Fruit Triangular, with three “wings.” Seed pods are shaped like inverted hearts, about ⅛" (3.2 mm) long.
Range/ Zones

USDA Zones: 5-8

Habitats Rivers, swamps, and other wetland regions. Wet areas and disturbed areas
Type Wild Wild

 

Online References:

Polygonum sachalinense on Discover Life

Polygonum sachalinense on the King County Washington Noxious Weeds list

Polygonum sachalinense on Wikipedia

Polygonum sachalinense on the USDA Forest Service's Fire Effects Information Database

Polygonum sachalinense on the USDA Plants Database

Polygonum sachalinense on CalPhotos

Polygonum sachalinense on Plants for a Future, a resource and information centre for edible and otherwise useful plants

Polygonum sachalinense description by Thomas H. Kent, last updated 16 Aug 2013.

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Range: Zones 5-8:

About this map...