Woolly Knotweed Plant Care
Persicaria lanigera (R.Br.) Soják
Updated · Sources · How we source care data
Persicaria lapathifolia, known as pale persicaria, is a plant of the family Polygonaceae. It is considered to be native throughout most of the world, from arctic to tropical realms, except South America and Southern Africa.
Every 3–5 days
Full sun to part shade
50–80°F
40–70%
At a glance
How do you care for Woolly Knotweed?
Water Woolly Knotweed every 3–5 days, letting the top layer of soil dry out between waterings, and give it full sun to part shade. It prefers temperatures of 50–80°F (10–27°C) and 40–70% humidity. Fertilize it every 6 months during the growing season.
What Is the Woolly Knotweed?
Woolly Knotweed (Persicaria lanigera) belongs to the Polygonaceae family within the Persicaria genus. Woolly Knotweed is also known as Woolly Smartweed.
Woolly Knotweed displays a spreading, clumping perennial growth habit, reaching up to 1.5 ft tall with a spread of approximately 2 ft. Woolly Knotweed produces small, spiky flowers in various colors.
Leaf size: approximately 4 inches.
How Often Should You Water a Woolly Knotweed?
Persicaria lanigera requires watering every 3–5 days. Allow the top layer of soil to dry between waterings to prevent root rot. Reduce watering frequency during winter when growth slows.
Watering Frequency
Every 3–5 days
Let soil partially dry between waterings
What Light Does the Woolly Knotweed Need?
Woolly Knotweed thrives in full sun to part shade.
Light Requirement
Full sun to part shade
What Temperature and Humidity Does the Woolly Knotweed Prefer?
Persicaria lanigera grows best at temperatures of 50–80°F. Woolly Knotweed prefers humidity levels of 40–70%.
Temperature
50–80°F
Humidity
40–70%
What Soil Mix Works Best for a Woolly Knotweed?
Moist, well-draining soil rich in organic matter. Good drainage is essential for Woolly Knotweed to prevent waterlogging, which leads to root rot and fungal issues.
How Often Should You Fertilize a Woolly Knotweed?
Feed Woolly Knotweed every 6 months during the growing season (spring and summer) with a balanced fertilizer diluted to the strength on the label.
Pause feeding in autumn and winter, when growth slows, and never fertilize dry soil — water first.
Fertilizing
Every 6 months
During the growing season
The PlantoScan app can remind you when to water and when to fertilize each plant.
How Do You Repot a Woolly Knotweed?
Repot every 2-3 years in early spring. Choose a pot one size larger than the current container, and ensure it has drainage holes to allow excess water to escape.
How Do You Propagate a Woolly Knotweed?
Woolly Knotweed can be propagated through division, seeds.
Is the Woolly Knotweed Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Woolly Knotweed, so we can't confirm whether it is safe for cats and dogs. Keep pets from chewing it as a precaution.
This is a general caution, not veterinary or medical advice. If your pet ate a plant, contact your vet or animal poison control.
See all plants toxic to cats and plants toxic to dogs.
What Pests and Diseases Affect the Woolly Knotweed?
Woolly Knotweed is susceptible to aphids, spider mites. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.
Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.
What USDA Hardiness Zone Does the Woolly Knotweed Need?
Woolly Knotweed grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. In cooler regions, grow Woolly Knotweed as a houseplant or bring it indoors before the first frost.
Hardiness Zone
Zone 12a
Keep exploring plants
Woolly Knotweed is one of many species covered in the complete plant care and identification guide, which groups plants by genus, attribute, and popularity.
It belongs to the Persicaria genus — compare its care with other Persicaria species on PlantoScan.
Persicaria is part of the Polygonaceae plant family — browse all Polygonaceae genera and species.
Woolly Knotweed thrives in bright light and direct sun — see other bright-light plants.
Related Plant Care Guides
Closely related plants with similar care requirements:
Sources
- Scientific name & taxonomy: Persicaria lanigera (R.Br.) Soják, family Polygonaceae (first published in Preslia 46: 153 (1974)) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Woolly Knotweed, so we can't confirm whether it is safe for cats and dogs. Checked against the ASPCA plant list; any other toxicity note on this page comes from PlantoScan's plant database.
- Hardiness zone: USDA Zone 12a, calculated from the plant's minimum temperature.
- Care values(watering, light, temperature, humidity, soil, fertilizing): PlantoScan's plant database, filtered by automatic plausibility checks — values that fail them are hidden. How we source and check plant data.
Spotted a mistake? Email info@upvision.media with the page link — we check and correct reported errors.
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