Polygonum scoparium

Polygonum or Persicaria scoparium is a very curious perennial plant from Mediterranean marshes that proves to be indifferent to summer drought, rather like the cane of Provence. The comparison stops there: forming a tuft of slender stems adorned with black rings, it rather resembles a horsetail. And when spring arrives, the tuft sags a bit and takes on the appearance of white broom, covered with a mist of small fragrant stars. It would be a shame not to try growing this unusual plant: give it sun, well-drained but moist soil during flowering, in a somewhat wild area of the garden or along the edge of a pond and prune it every 2 or 3 years.

Polygonum scoparium is a plant of the Polygonaceae family native to marshy and occasionally waterlogged areas of Sardinia and the west coast of Corsica. The genus name, Polygonum, refers to the morphology of the stems: from the Greek poly, "several", and gonu, "knee", because of the swollen nodes that segment the stem along its entire length. The epithet scoparium is related to the stiff and slender appearance of the stems, which resemble those of broom plants. This rhizomatous plant is not invasive. It forms a persistent tuft that is tall and wide, composed of bare, erect, unbranched, smooth, cylindrical, very thin stems, almost devoid of leaves. They are a slightly greyish olive-green, adorned with darker nodes arranged at regular intervals. Flowering takes place in April-May in Mediterranean climates, before the arrival of heat and drought, and sometimes again in September, with the return of rain. Elsewhere, the plant flowers from June to September. The flowers are arranged along the entire length of the stems. They are very small, white star-shaped flowers touched with pink and yellow stamens.

Hardy in zone 7 (down to -15 °C (5 °F)) and loving waterlogged soils, Polygonum scoparium will find its rightful place near water features, alongside Gomphostigma virgatum, which resembles it a bit but is less cold-tolerant. But it also adapts very well in flower beds, in any well-drained ordinary soil, as long as it does not lack water during its growth, and even in dry soil during summer. Its origins also make it suitable for ornamental gardens in Mediterranean climates and coastal areas, with occasional watering. It can be associated, for example, in moist soil, with horsetails, Carex pendula, and cannas to add an exotic touch, as well as Euphorbia palustris. In a natural or country-style flower bed, it will also accompany Alliums for a contrast of patterns, the purple stars of tall asters (Aster turbinellus), and Verbena hastata Rosea with fabulous autumn colours. It is an easy perennial that requires little monitoring and proves to be long-lasting.