- Family: Primrose Family – Primulaceae
- Growing form: Perennial herb. Rhizomatous, short runners–almost runnerless.
- Height: 30–100 cm (12–40 in.). Stem quite erect from base, unbranched, upper part finely haired, lime green–reddish brown, often dotted.
- Flower: Corolla wheel-shaped, yellow, 12–20 mm (0.5–0.8 in.) wide, fused, short-tubed, 5-lobed, lobes with tapered tips, edge glandular-hairy. Calyx lobes narrow, completely green or red. Stamens 5. Gynoecium fused, single-styled. Inflorescence a lax, terminal, compound raceme. Flowers solitary or in pairs.
- Leaves: In whorls or opposite, quite long-stemmed. Leaf blade ovate–elliptic, quite round-tipped, with entire margins, darkly spotted, finely haired underside.
- Fruit: Spherical, 5-valved, longer than calyx, approx. 4 mm (0,2 in.) long capsule.
- Habitat: Gardens, parks, roadsides, ditches, wasteland. Ornamental and escape.
- Flowering time: June–September.
There are around 150 species in the Lysimachia genus, of which 14 grow in Europe. It’s no wonder that dotted loosestrife is so popular: the species demands almost no attention at all, it’s tough, overwinters well, is suited to a wide range of habitats and spreads profusely along runners, not to mention that it’s very fetching when it’s in flower.
Dotted loosestrife can be confused with yellow loosestrife (L. vulgaris), which is almost as beautiful. Yellow loosestrife is usually taller however, its leaves have shorter stalks, are sharp-tipped, and are clearly smaller at the top than they are lower down. The flowers appear in dense groups, the corolla lobes have glabrous hairs, and the calyx lobes often have red margins. Other Lysimachias are sometimes grown in Finland as ornamental plants, including limp-stemmed creeping Jenny (L. nummularia), which often escapes into the wild, and fringed loosestrife (L. ciliata) which resembles dotted loosestrife and escapes only rarely.
Fringed loosestrife is native to North America where this perennial species thrives in damp places. It looks a lot like dotted loosestrife and also yellow loosestrife. In Finland fringed loosestrife is quite rare garden plant which sometimes may escape to the wild. It differs from dotted loosestrife with its glabrous stem and especially lighter flower colour. Also red-coloured varieties exist.