Pennsylvania smartweed
Family
PolygonaceaeScientific Name
Polygonum pensylvanicum
Other Common Names:
pinweed
Pennsylvania knotweed
Synonyms (former Scientific Names):
Polygonum mexicanum
Persicaria longistyla
Polygonum mississippiense
Polygonum longistylum
Persicaria pensylvanica
Persicaria mississippiensis
Polygonum bicorne
Persicaria bicornis
Habit
An up-right branched plant reaching heights of 1 to 4 feet with a shallow tap root and fibrous secondary roots. This species spreads by seed germinating in the early to late spring.
Leaves
Usually lance shaped with very short stalks and one prominent vein in the center.
Identifying Characteristics
This species has large nodes where each alternate leaf is attached with a papery sheath surrounding the attachment.
Flower Seed Head
Found in a spike-like terminal cluster, flowers are usually pink to white.
Seed Fruit
Achenes house the shiny, black, flat, tear-shaped seeds measuring 3 mm.
Where Found
Throughout the United States this plant is usually not a factor in turf. However, it plagues landscapes, horticultural, and agronomic crops as well as nurseries.
Growth Habit
upright and nonwoody
Thorns or Spines
not present
Approximate Flower Diameter
dime
Dominant Flower Color
pink
Flower Symmetry
radial symmetery
Leaf Hairs
has hairs
Leaf Shape
lance
Leaf Arrangement
alternate
Leaf Margin
entire
Leaf Structure
simple
Leaf Stalk
shorter than leaf
Stem Hairs
has hairs
Stem Cross Section
round or oval
Milky Sap
not present
Root Structure
taproot
Life Cycle
summer annual
Ochrea
present
Plant Type
Herb