Also known as Knotweed · 61 saves
Polygonum
Polygonum, the genus most gardeners know as knotweed. We track 5 varieties; the ones most used by real gardeners.
The 5 most-saved Polygonum varieties
3 species of Polygonum
Each one is a parent of the varieties above.
Track your Polygonum in Sow
Save the Polygonum you grow and get care reminders timed to your zone.
How to grow Polygonum
Whats common across all Polygonum varieties in our catalog — drawn from the care records of the 5 most-grown of them.
The Polygonum year
- Spring CleanupMarch and April60% of varieties
Remove any dead, tangled, or unwanted growth before new shoots appear
- PlantMay40% of varieties
Plant containerized or bare-root vines in spring or fall
- Check for PestsJune and July40% of varieties
Monitor for powdery mildew in shaded or poorly drained areas.
- Winter PrepOctober and November40% of varieties
Remove mature plants before they drop seed to reduce next year's population.
Do
- Water during dry spells 🌱
- Prune to maintain shape
- Provide support for climbing
- Fertilize monthly during growth
- Sever the taproot below the crown to ensure complete removal of mature plants.
Avoid
- Overwater to prevent root rot ❌
- Allow plant to become waterlogged
- Neglect pruning
- Plant in poorly drained soil
What goes wrong with Polygonum
| Problem | What you'll see | What to do |
|---|---|---|
| Aphids | Sticky residue and distorted leaves | Use insecticidal soap or neem oil |
| Spider Mites | Fine webbing on leaf undersides and yellow stippling on the foliage during hot, dry weather. | Increase local humidity and spray the undersides of leaves thoroughly with water or horticultural oil. |
| Spider mites | Fine webbing on foliage and stippled, yellowing leaves under hot, dry conditions. | Increase humidity around the area or apply horticultural oils to manage populations. |
| Root rot | Wilting and blackened roots | Improve drainage and reduce watering |
| Powdery Mildew | White, powdery fungal patches on the upper surfaces of leaves. | Improve air circulation around the plants and avoid overhead watering to keep foliage dry. |
| Root Rot | Wilting, yellowing foliage and mushy, blackened roots in stagnant water. | Ensure the soil has adequate drainage to prevent water from pooling and becoming stagnant. |
Making more Polygonum
cuttings
- Select healthy stems in early summer.
- Cut 4-6 inch sections and remove lower leaves.
- Dip in rooting hormone.
- Plant in moist, well-drained soil.
- Keep soil moist for 6 weeks.
Seed
- Collect mature black achenes from dried flower spikes in autumn.
- Store seeds in a cool, dry location over winter.
- Sow seeds directly onto moist, disturbed soil in early spring.
- Keep the seedbed damp until germination occurs as temperatures rise.
Polygonum questions
How many types of Polygonum are there?
The Sow catalog tracks 5 distinct Polygonum varieties. The most popular — ranked by 61 real gardeners — are shown first above.
What zones does Polygonum grow in?
Across its varieties, Polygonum covers USDA Zones 4–10. Individual varieties differ — each plant page lists its exact range, and Sow filters the catalog to your zone automatically.
When does Polygonum bloom?
Most Polygonum varieties bloom in summer to fall, mid-summer, summer. Staggering early, mid, and late varieties extends the genus's season in one bed.
Which Polygonum should I choose?
Start from the most-saved varieties above — popularity across thousands of gardens is a strong signal of reliability — then filter by your zone and sun. In the Sow app you can preview any of them in a photo of your actual yard before you buy.