Lysimachia thyrsiflora

Lysimachia thyrsiflora is a vigorous perennial that is ideal for aquatic environments or wetlands. It thrives on banks or in water no deeper than 10cm (4in). It develops tender green leaves. Between May and July, it bears inflorescences in dense spikes, formed by small yellow flowers. It is extremely hardy and spreads easily in heavy, moist, marshy soil. It is perfect for enriching the biodiversity of ponds and natural bodies of water.

Lysimachia thyrsiflora is a member of the Primulaceae family, like primroses and cyclamen. Native to cold regions, this species thrives in marshes and along rivers, especially in northeastern and central Europe. It is also widespread in Canada and the northeastern United States, as well as Siberia, although more sporadically.

It is a perennial plant with suckering roots. It develops stiff, erect stems up to 0.5 to 0.6m (1.6 to 2ft) in height. The stems are cylindrical, scaly at the base, then leafy in their aerial part. The dull green leaves, 7 to 10cm (3 to 4in) long, are opposite, narrow and elongated. The leaves display veins on the underside. The flowering period is brief, lasting only two to three weeks in between April and May. The flowers gather in yellow clusters at the end of long peduncles emerging from the axils of the middle leaves. These clusters, called thyrses, are made up of an arrangement of flowers arranged in cymes.

It is a frost-hardy plant that thrives in moist environments such as ponds, rivers, marshes, and lagoon areas. This plant thrives in full sun, in various types of soil that are rich in humus. It is happy in water at a depth of 5 to 10cm (2 to 4in). In a garden, it can be planted at the edge of a pond, in the heart of marshy areas, among pebbles or rocks, in a humid environment, or even in a few centimetres of stagnant water. It is easy to cultivate and spreads by runners. It can become invasive, so requires precautions to control its spread. To create a harmonious aquatic scene, you can combine it with plants adapted to banks or shallow waters, such as Juncus effusus 'Spiralis', Pontederia cordata, Lobelia cardinalis, Rumex sanguineus, Acorus calamus, Iris pseudacorus, and wetland grasses such as Carex pendula or cottongrass (Eriophorum angustifolium).