Douglas' Knotweed
Polygonum douglasii
- Native to:
- Canada, Mexico, United States
Matt Lavin (flickr.com)
Taxonomy
- Division:
- Magnoliophyta | - Flowering plants
- Family:
- Polygonaceae
- Genus:
- Polygonum
- Species:
- Polygonum douglasii
- USDA Symbol:
- PODO4
Growth Characteristics
- Life Cycle:
- Annual
- Growth Habit:
- Forb/herb
- Height:
- 60 cm
- Light Requirements:
- Full Sun
- Drought Tolerance:
- High
- Bloom Months:
- jun,jul,aug,sep
- Bloom Colors:
- white, pink, green
Wildlife Benefits
- Caterpillars:
- ★☆☆☆☆ Recorded caterpillar host plant (HOSTS Database)
Host Plant for Caterpillars
Epidemia helloides, Epidemia mariposa, Epidemia nivalis
Garden & Ecology Notes
- Wildlife Value:
- birds
- Deer Resistant:
- Yes
- Fire Ecology:
- Fire adapted — tolerates or benefits from fire
- Fire Notes:
- Resprouts from root crown after fire; common in disturbed and post-fire habitats.
Soil Requirements
- Soil Type:
- sandy, well-drained, nutrient-poor soil
- pH:
- 5.5 - 7.5 (slightly acidic to neutral)
- Drainage:
- excellent drainage required
- Moisture:
- dry to moderate
- Notes:
- Commonly found in disturbed areas and open habitats.
Propagation & Germination
- Stratification:
- Cold/moist stratification required — 30–60 days
- Germination Time:
- 14–30 days
- Notes:
- Seeds germinate readily after cold stratification. Light may enhance germination.
The above propagation data sourced from Claude AI
Pre-treatment: Seeds are placed in cold moist stratification for 60 days.
Establishment: P. douglasii is found from British Columbia to Colorado. There are 7 recognized botanical varieties. Germination was greater in light than on dark.
Source: npn.rngr.net