marshpepper knotweed
Polygonum hydropiper · Polygonaceae
marshpepper knotweed (Polygonum hydropiper) is a annual herbaceous plant in the Polygonaceae family. It is introduced to North America rather than native. USDA records it as hardy in zone 12 and warmer, down to about 52°F.
At a glance
| Type | forb-herb USDA |
|---|---|
| Lifecycle | annual USDA |
| Native status | introduced USDA |
| Mature height | 1.6 ft USDA |
| Light | full-sun USDA |
| Water need | high USDA |
| Growth rate | rapid USDA |
| Soil pH | 5–7.5 USDA |
| Bloom | May–June USDA |
| Flower color | Red USDA |
| Hardiness zones | 12 and warmer USDA |
| Guild layer | ground-cover 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 needs consistently moist ground. It is recorded on soils from pH 5 to 7.5 — a broad range that spans acidic through mildly alkaline ground. Its cold limit is zone 12; USDA publishes no warm-end limit, so gardeners in warmer zones should check local heat tolerance separately.
Size and growth
At maturity it reaches about 1.6 ft, making it a low, mat-forming plant. It grows quickly, which matters when you are timing a planting around the layers above it.
Bloom period
USDA records a bloom period of May through June. The flower color USDA records is red. Bloom timing is how the Guild Builder overlaps flowering across a planting so something is in flower for as much of the season as possible.
Bloom period is a claim about when this plant flowers. It is deliberately not a pollinator rating — no dataset we trust publishes one, so we do not make that claim. See Data & sources.
Role in a guild
Ground cover. In a layered planting this is the lowest layer — it shades soil, holds moisture, and suppresses weeds. We derive the layer from the plant's growth habit and mature height using a fixed rule, so the same inputs always produce the same layer.
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
- bearded beggarticks Bidens aristosa
- crowned beggarticks Bidens coronata
- smooth beggartick Bidens laevis
- golden tickseed Coreopsis tinctoria
- annual hairgrass Deschampsia danthonioides
Where this data comes from
Every value on this page comes from the USDA PLANTS database record for symbol POHY, 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.
bloom_end— quoted from USDA PLANTSbloom_start— quoted from USDA PLANTScommercial_availability— quoted from USDA PLANTSduration— quoted from USDA PLANTSflower_color— quoted from USDA PLANTSgrowth_habit— quoted from USDA PLANTSgrowth_rate— quoted from USDA PLANTSguild_role— derived by rule from USDA columnsmature_height_ft— quoted from USDA PLANTSmoisture— quoted from USDA PLANTSnative_status— quoted from USDA PLANTSnitrogen_fixer— quoted from USDA PLANTSpet_safe— quoted from USDA PLANTSph_max— quoted from USDA PLANTSph_min— quoted from USDA PLANTSshade_tolerance— quoted from USDA PLANTStemperature_min_f— quoted from USDA PLANTSzone_min— quoted from USDA PLANTS
Read our full data sources and methodology.
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