Pink knotweed
Persicaria capitata · Polygonaceae
📷 JJ Harrison (https://www.jjharrison.com.au/) · CC BY-SA 3.0
The gardener's calendar
Pink knotweed is in full bloom: enjoy it, watch watering in hot weather and let spent flowers feed pollinators before pruning.
ID card
- Scientific name
- Persicaria capitata
- Family
- Polygonaceae
- Type
- Perennial herbaceous plant
- Mature height
- 40 cm
- Flowering
- June to September
- Foliage
- Deciduous
- Hardiness
- Moderate (frost tender in cold regions)
- Origin
- Himalayas (India, Nepal)
✓ Taxonomy verifiedSource: AI estimate · hardiness: reliability medium.
Expert tips
The key tip
Bistorta capitata appreciates light soil and moderate moisture in summer. Deadhead faded flower spikes to extend flowering until the first frosts.
The common mistake
Planting it in heavy or too-dry soil: it slowly declines and flowers poorly, you think it dislikes your conditions when it just needs better aeration.
The pro's trick
In dry summers, light evening watering (not in the morning) significantly increases flower production; this is a generous plant that responds immediately.
Seasonal watch
In autumn (September-October), it forms rhizomes that can spread slightly through suckering.
Care
Sunlight
Bistorta capitata loves full sun exposure for optimal flowering. It tolerates partial shade but will flower less abundantly. Position it in an open spot where it receives at least 6 hours of direct sunlight daily.
Watering
Keep the soil consistently moist during the growing season, without waterlogging it. Water regularly during dry spells or summer heat. In winter, reduce watering. Drainage must be adequate to prevent root rot.
Soil
This plant prefers rich, well-draining soil that is slightly acidic. Adding compost or potting soil at planting will improve growth. Enrich the base annually with organic matter to maintain soil fertility.
Fertilizing
Apply balanced fertilizer in spring when growth starts. You can give a light application in early summer to support flowering. Avoid excess nitrogen, which would promote foliage at the expense of flowers.
Pruning and cleanup
Remove spent flowers regularly to extend the flowering period. In late autumn or early winter, cut stems back to ground level. In spring, clean up debris and weak new growth.
Pests and diseases
Bistorta capitata is generally robust. Watch for excessive watering that could promote powdery mildew or rot. Good spacing and air circulation limit fungal problems.
Did you know?
Bistorta capitata is sometimes called 'mountain bistorta' by botanists because of its close relatives in the Bistorta genus. Native to the mountainous Himalayan regions, it bears small pink flowers in compact spikes that are highly attractive to bees and butterflies throughout summer.
Where to buy it
Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.
Add this plant to my garden →Plants from the same family
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- Red bistortBistorta amplexicaulis
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Tips generated and checked by Viridia — adapt them to your local climate.