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Koenigia ×fennica
Finnish knotweed is a hybrid perennial of the knotweed family, grown as an ornamental plant that reaches about 1.5 to 2 m and bears creamy white flowers that turn pink. It is mainly known in cultivation, with the cultivar 'Johanniswolke' the most common form.
Koenigia × fennica, known as Finnish knotweed, is a hybrid between two species of Koenigia, K. alpina and K. weyrichii, members of the family Polygonaceae, the knotweed family. It generally only known as a cultivated garden plant, but plants have been recorded a few times surviving in abandoned areas in northern Europe, especially in Finland. The cultivar 'Johanniswolke' is considered an attractive ornamental perennial plant.
The cultivar 'Johanniswolke' first appeared in Germany in the early 2000s as Aconogonon 'Johanniswolke', supposedly as a collection from Asia. It is often classified as "A. speciosum" in horticulture. Around the same time the hybrid was also being sold elsewhere in Europe under the name "Polygonum polymorphum" or "Persicaria polymorpha", and different other combinations of these names now exist in horticulture. Neither P. polymorpha nor Aconogonon speciosum exist as valid taxonomic names, these are horticultural inventions, whereas Polygonum polymorphum is a synonym of the related Koenigia alpina. The plant has been called "white dragon knotweed" in the USA.
This plant is grown as an ornamental perennial. It grows to a height of 150–200 cm (4 ft 11 in – 6 ft 7 in). Flowering in June, or July to August in far northern latitudes, it has creamy white flowers which turn pink as they age. Although shrub-like in appearance, it is herbaceous, dying back to the ground over winter.
It was widespread in cultivation in Nordic countries, especially Finland, when first described in 1999. The first plants appeared in the 1970s in Finland. Reiersen in 2000 recorded over 100 instances of it being found in Finland, a dozen or so each in Norway and Denmark, and twice in Sweden. By 2018 it had been found 514 times in Finland. It is recorded as a "new resident alien" in the 2019 Checklist of the Vascular Plants of Finland, and "spreading in the wild". It has only been found once as a garden escape in Britain, a plant found in 1981 in Yorkshire. In Belgium it has been sighted twice as a garden escape on abandoned grounds, both in 2014.
Koenigia alaskana · Alpine Knotweed · Bellflower Knotweed · Davis's Knotweed · Island purslane · Sikkim Knotweed · Koenigia phytolaccifolia · Chinese Knotweed · Knotweed · Koenigia polystachya
Text excerpted from the Wikipedia article Koenigia × fennica by its contributors, under CC BY-SA 4.0; the excerpts and the care summary drawn from them are shared under the same licence.
The care summary was written by AI (Claude, Anthropic) from the sources on this page, with general growing knowledge where they are silent. Check before relying on it.
