Pennsylvania Smartweed (Pensylvanicum)

The Pennsylvania Smartweed (Pensylvanicum) is generally described as an annual forb/herb. This is native to the U.S. (United States) has its most active growth period in the summer . The Pennsylvania Smartweed (Pensylvanicum) has green foliage and inconspicuous red flowers, with a moderate amount of conspicuous black fruits or seeds. The greatest bloom is usually observed in the spring, with fruit and seed production starting in the spring and continuing until fall. Leaves are not retained year to year. The Pennsylvania Smartweed (Pensylvanicum) has a short life span relative to most other plant species and a moderate growth rate. At maturity, the typical Pennsylvania Smartweed (Pensylvanicum) will reach up to 3.9 feet high, with a maximum height at 20 years of 0 inches.

The Pennsylvania Smartweed (Pensylvanicum) is easily found in nurseries, garden stores and other plant dealers and distributors. It can be propagated by seed. It has a rapid ability to spread through seed production and the seedlings have medium vigor. Note that cold stratification is not required for seed germination and the plant cannot survive exposure to temperatures below 32°F. has medium tolerance to drought and restricted water conditions.

Uses of : Landscaping, Medicinal, Culinary, etc.

This plant is an excellent wildlife food plant, especially for waterfowl. Twenty species of ducks, geese, bobwhites, mourning doves, ring-necked pheasants, and four species of rails, as well as 30 nongame birds, eat the seeds. Dense stands provide cover for young waterfowl, marsh birds, and wintering pheasants. Plants and/or seeds are eaten by white-footed mice, muskrat, raccoons, and fox squirrels.

General Characteristics

Knotweed Family (Polygonaceae). Pennsylvania smartweed is an annual herb that has small, five-parted pink or rose colored flowers on a short spike. It grows 2 to 4(6) feet high. The flowering branches have stalked glands. The stems have a reddish color and swollen nodes. The alternate leaves have sheaths extending around the stems. The seeds are black, shiny, flattened, and almost round. There are approximately 62,000 seeds per pound.

Required Growing Conditions

Pennsylvania smartweed is adapted to soils of all drainage classes except droughty soils. It commonly occurs on mudflats of fresh water to moderately brackish areas throughout the Northeast.

Pennsylvania smartweed is distributed throughout the entire Unites States, excluding a few northwestern states. For a current distribution map, please consult the Plant Profile page for this species on the PLANTS Web site.

Cultivation and Care

A seedbed that reduces most weed competition and permits smartweed to be covered by one inch of soil depth is usually sufficient. Drop water quickly and broadcast seed on top of wet ground in mudflats or drawdown areas. Seed after the last killing frost in the spring. Smartweed may be seeded later so that seed maturity coincides with the arrival of migratory birds. Seeds are generally broadcast at a rate of 10-15 pounds per acre.

General Upkeep and Control

As an upland wildlife food source, plant either in pure stands or in mixtures with other suitable and adapted species. For waterfowl food, draw down water where necessary shortly before planting. Do not re-flood until plants are at least 6 inches in height. Flood the area to a depth of 12-18 inches during the migratory season. Re-plant annually to assure a uniform stand. A light harrowing is recommended to encourage natural re-establishment of stands.

Cultivars, Improved, and Selected Materials (and area of origin) No varieties exist, but common seed may be obtained through wildlife and game food seed dealers.

Plant Basics
Growth Rate Moderate
General Type Forb/herb
Growth Period Summer
Growth Duration Annual
Lifespan Short
Plant Nativity Native to U.S.
Commercial Availability Routinely Available
Physical Characteristics
Bloom Period Spring
Displays Fall Colors No
Shape/Growth Form Single Crown
Drought Tolerance Medium
Shade Tolerance Intolerant
Height When Mature 3.9
Vegetative Spread None
Flower Color Red
Flower Conspicuousness Yes
Fruit/Seed Abundance Medium
Fruit/Seed Seasonality Spring Fall
Seed Spread Rate Rapid
Gardening Characteristics
Propagations (Ways to Grow) Seed
Moisture Requirements Medium
Cold Stratification Required No
Minimum Temperature 32
Soil Depth for Roots 14
Toxic to Nearby Plants No
Toxic to Livestock No
After-Harvest Regrowth Rate Slow
After-Harvest Resprout Ability No
Responds to Coppicing No
Growth Requirements
pH Range 4–8.5 pH
Precipitation Range 12–12 inches/yr
Planting Density 0–0 indiv./acre
Soil Textures Coarse, Fine, Medium
Soil Depth for Roots 14
Minimum Frost-Free Days 95 day(s)
Salinity Tolerance Low
CaCO3 Tolerance Medium
Sustainability & Use
Leaf Retention No
Fire Resistant No
Causes Livestock Bloating None

Source: USDA, NRCS, PLANTS Database,
National Plant Data Center, Baton Rouge, LA 70874-4490 USA