Lysimachia vulgaris aka Garden Loosestrife

Lysimachia vulgaris is a herbaceous perennial: a plant whose soft top growth dies back each year. It belongs to the primrose family, Primulaceae. People call it yellow loosestrife or garden loosestrife. Its native range spans Europe, Siberia and the western Himalaya. Britain and Ireland lie within its native range. It grows in marshes, wet woods and along streams. It also grows by ponds and in shallow water. Garden plants have escaped into damp sites in North America.

Plants form clumps of stiff stems that stand upright. Creeping rhizomes, or underground stems, help the clumps spread. Garden height is about 3–5 feet [0.9–1.5 metres]. Some plants reach 6 feet [1.8 metres]. Reports give a spread of 1.6–6 feet [0.5–1.8 metres]. Groups can spread farther as the rhizomes grow. Hairs cover the green leaves and stems. Leaves range from oval to lance-shaped, like a spear tip. They grow in opposite pairs or rings called whorls. Each whorl holds three to five leaves. Small black or orange oil glands dot the leaves. The leaves die back when the season ends.

Yellow flowers with reddish-brown centres grow in groups at stem tips. The plant blooms from June to September. This long show of blooms gives it its main garden value. It suits bog gardens, pond edges and stream banks. Sources also suggest wild gardens and damp, remote border sites. Yet its spread can outweigh the worth of its blooms. Keep it apart from prized perennials where groups can spread.

Grow it in rich soil that stays moist to wet. It copes with clay, loam and soil that drains poorly. Full sun and part shade both suit it. Shade after noon helps where summers are hot. RHS lists it as H6, hardy across Britain and northern Europe. Missouri Botanical Garden gives USDA zones 4–8. Grow new plants from seed or by splitting clumps. You may cut back stems when the season ends. Both garden sources say serious pest and disease problems are rare.

Spreading rhizomes and self-sown seedlings can make this plant invasive. Dense groups can crowd out native plants and harm wetlands. Underground growth can be hard to remove once it takes hold. PFAF lists young leaves as edible but gives no preparation details. It reports no known hazards. This does not mean the plant is safe for pets. PFAF also notes past use as medicine for gut problems and bleeding. These records do not prove that treatment is safe or works. Flowers give yellow dye, while rhizomes give brown dye.