Also known as Knotweed · 460 saves
Persicaria
Persicaria, the genus most gardeners know as knotweed. We track 12 varieties; the ones most used by real gardeners.
The 12 most-saved Persicaria varieties
3 species of Persicaria
Each one is a parent of the varieties above.
Track your Persicaria in Sow
Save the Persicaria you grow and get care reminders timed to your zone.
How to grow Persicaria
Whats common across all Persicaria varieties in our catalog — drawn from the care records of the 12 most-grown of them.
The Persicaria year
- DivideMarch and September100% of varieties
Divide clumps every 3-4 years in spring or early fall to rejuvenate
- Spring CleanupFebruary and March83% of varieties
Cut back old stems to the ground before new growth begins
- PlantMarch, April, September and October58% of varieties
Plant in spring or early fall; prefers moist soil
- MulchMarch50% of varieties
Apply 2-3 inches of organic mulch to help retain soil moisture
- DeadheadJune–September50% of varieties
Remove spent flower spikes to tidy the plant and limit vigorous self-seeding.
- FertilizeMarch33% of varieties
Apply a balanced, slow-release fertilizer in early spring
Do
- Water regularly to keep soil moist 🌱
- Water regularly to keep soil moist but not waterlogged 🌱
- Water consistently to keep soil moist 🌱
- Prune after flowering to maintain shape
- Provide full sun for optimal flowering
Avoid
- Avoid letting soil dry out completely ❌
- Avoid overwatering to prevent root rot ❌
- Don’t fertilize in late fall
- Never cut back in late season to prevent winter damage
What goes wrong with Persicaria
| Problem | What you'll see | What to do |
|---|---|---|
| Aphids | Sticky residue and distorted leaves | Use neem oil spray or insecticidal soap |
| Slugs | Irregular holes on leaves | Use iron phosphate bait or handpick |
| Spider Mites | Fine webbing on foliage | Increase humidity and spray with horticultural oil |
| Powdery Mildew | White powdery coating on leaves | Improve air circulation and apply organic fungicide |
| Root Rot | Wilting and yellowing leaves | Ensure well-draining soil and reduce watering |
| Leaf spot | Dark spots on leaves | Remove affected leaves and improve air circulation |
Making more Persicaria
Division
- Dig up mature plant in early spring or fall.
- Gently separate clumps with a sharp knife or spade.
- Replant divisions immediately in prepared soil.
- Water thoroughly after planting.
- Wait 4–6 weeks for new growth to establish.
Cuttings
- Take softwood cuttings in late spring or early summer.
- Dip cut ends in rooting hormone.
- Plant in moist potting mix.
- Keep soil moist and place in bright, indirect light.
- Roots develop in about 6 weeks.
Persicaria questions
How many types of Persicaria are there?
The Sow catalog tracks 12 distinct Persicaria varieties. The most popular — ranked by 460 real gardeners — are shown first above.
What zones does Persicaria grow in?
Across its varieties, Persicaria covers USDA Zones 4–9. Individual varieties differ — each plant page lists its exact range, and Sow filters the catalog to your zone automatically.
When does Persicaria bloom?
Most Persicaria varieties bloom in late summer, mid-summer to fall, summer to fall. Staggering early, mid, and late varieties extends the genus's season in one bed.
Which Persicaria 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.