Pennsylvania smartweed
Polygonum pensylvanicum · Polygonaceae
Pennsylvania smartweed (Polygonum pensylvanicum) is a annual herbaceous plant in the Polygonaceae family. It is native to North America. USDA records it as hardy in zone 10 and warmer, down to about 32°F.
At a glance
| Type | forb-herb USDA |
|---|---|
| Lifecycle | annual USDA |
| Native status | native USDA |
| Mature height | 3.9 ft USDA |
| Light | full-sun USDA |
| Water need | medium USDA |
| Growth rate | moderate USDA |
| Soil pH | 4–8.5 USDA |
| Bloom | March–May USDA |
| Flower color | Red USDA |
| Hardiness zones | 10 and warmer USDA |
| Guild layer | herb-layer Derived |
| Nursery availability | Routinely Available USDA |
USDA quoted from the USDA PLANTS database · Derived computed by a fixed rule from those columns. No value on this page is estimated.
Growing conditions
It needs full sun. USDA rates it as having moderate water needs. Its drought tolerance is rated medium. It handles periodically wet ground (USDA rates its anaerobic tolerance medium). It is recorded on soils from pH 4 to 8.5 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 10.
Size and growth
At maturity it reaches about 3.9 ft, making it roughly waist to chest height. It grows at a moderate rate.
Bloom period
USDA records a bloom period of March through May. Flowers are red.
A flowering date, not a pollinator rating.
Foliage, flower and season
Summer foliage is green, medium in texture. Its flowers are conspicuous. Its active growth period is summer.
What the site needs to provide
USDA records it across sites receiving 12 to 60 inches of annual precipitation. The low end of that band is genuinely arid, so it has a wide tolerance for dry country. It needs at least 95 frost-free days to finish its season. It roots to at least 14 inches. Fertility requirement: medium.
Propagating it
Seed is the only propagation method USDA lists. Division and cuttings are not listed as options. USDA records no cold-stratification requirement, so seed should germinate without a chilling period. Its seed spreads at a rapid rate. It does not spread vegetatively, so it will stay where you put it.
Resilience and wildlife
Its fire tolerance is rated high. Its growth form is recorded as single crown.
Role in a guild
Herb layer. In a layered planting this is the herbaceous middle — perennials and grasses that fill the space between ground cover and shrubs. The layer is derived by a fixed rule from growth habit and mature height.
Tags
Related plants
Others in Polygonum
- water knotweed Polygonum amphibium
- meadow bistort Polygonum bistorta
- American bistort Polygonum bistortoides
- Davis' knotweed Polygonum davisiae
Similar role and hardiness
- pineapple Ananas comosus
- clasping coneflower Dracopis amplexicaulis
- Indian blanket Gaillardia pulchella
- jewelweed Impatiens capensis
- Bigelow's tansyaster Machaeranthera bigelovii
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol POPE2, or is computed from those values by a fixed rule. Nothing here is estimated or model-generated. Where USDA publishes no value, this page omits the claim rather than filling the gap.
- Quoted from USDA PLANTS: active growth period, Bloom, Bloom end, cold stratification, Drought tolerance, fall conspicuous, fertility requirement, fire tolerance, Flower color, flower conspicuous, foliage color, foliage porosity winter, foliage texture, frost free days min, fruit conspicuous, growth form, Growth rate, Hardiness zones, Lifecycle, Light, Mature height, Minimum temperature, Native status, Nitrogen fixation, Nursery availability, precipitation max in, precipitation min in, propagation, resprout ability, root depth in, seed spread rate, Soil pH, Soil pH (upper), Tolerance of wet soil, Toxicity, Type, vegetative spread rate, Water need.
- Derived by a fixed rule from those columns: Guild layer.
Read our full data sources and methodology.
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