Polygonum (Knotweed): How to Grow It, Even in Pots

POLYGONUM

Polygonum (Knotweed), also known as knotweed, is a rich genus of herbaceous annual and perennial plants, as well as deciduous climbers with numerous small flowers. Two of the most commonly used climbing species are Polygonum baldschuanicum and Polygonum multiflorum . The deciduous leaves are pale green, glossy, ovate, with a serrated edge, and the pale pink or white flowers bloom in abundance from early July to late September. The branches twine around supports of any kind. The fruits are achenes, contain a single seed, and appear after flowering, in autumn.

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HOW TO GROW

Growing Polygonum is recommended for decorating balconies, columns, walls, gates, trellises, and fences. Plants should be spaced 2 to 4 meters apart, keeping in mind that they will easily reach a height of around 5 meters. Polygonum pairs well with hellebores and hydrangeas.

EXPOSURE AND CLIMATE

In the North, during the winter, Polygonum multiflorum should be protected by covering the rhizomes with a layer of straw or leaves . Polygonum baldschuanicum grows well everywhere, from the Mediterranean area (even along the coast) up to 1000 meters above sea level in the North and 1300 meters in the South, in well-exposed and sheltered locations. It is best to place it in partial shade or full sun.

SOIL AND CULTIVATION CARE

Knotweed prefers cool, fertile soil and grows well even in calcareous soil. It requires no special care. 

IRRIGATION

It should be watered only when necessary. The plant generally thrives on rainfall, and in autumn and winter it goes into dormancy. Watering is therefore only necessary during the summer months and when the soil appears very dry.

SOWING AND FLOWERING

Propagation occurs by seed, layering, and semi-ripe and mature wood cuttings. Flowering occurs from July to the end of September. After flowering, pruning can be done by removing dead branches.

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POT CULTIVATION

To grow in a pot, Polygonum requires a generously sized container, rich in soil containing sand and expanded clay. Water only when the soil is completely dry. Repotting should be done in spring, using larger containers, when the roots emerge from the drainage holes.

Cover image source: Wikipedia

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