Gratiola officinalis aka Gratiole

Gratiola officinalis, or hedge hyssop, belongs to the Plantaginaceae family. It is a perennial herb from temperate regions. Its native range spans Europe to northern Xinjiang and northern Pakistan. It also grows wild in Morocco. It is not native to Britain or Ireland. Wild habitats include wet grasslands, fens, river banks, and ditches. These sites reflect its need for soil that holds moisture.

The plant forms clumps of upright stems from rhizomes. These are underground stems that support its perennial growth. The RHS describes plants reaching about 1.3 feet [0.4 metres] tall. Its garden size range reaches 1.6 feet [0.5 metres] in height and width. Plants take two to five years to reach full size. The leaves are narrow, ranging from linear to lance-shaped. Their edges have teeth, and the foliage dies back each year. Small white flowers appear in summer among the upright stems.

Grow hedge hyssop in full sun or partial shade. It suits clay, loam, or sand that retains moisture. The soil may be acidic, neutral, or alkaline. It tolerates poor drainage as well as moist, well-drained soil. Bog gardens and pond edges provide suitable growing sites. The RHS gives it a UK hardiness rating of H5. This indicates winter tolerance around 5–14°F [-15 to -10°C]. It can grow in exposed or sheltered positions. East-, south-, and west-facing sites are all listed as suitable.

Its clumped shape suits beds in informal and cottage gardens. The RHS also lists it for wildlife gardens. Damp borders offer another place to grow it. PFAF includes sunny woodland edges and sites with dappled shade. Raise new plants from seed or divide existing clumps. Cut back dead growth after the leaves die in autumn. The RHS reports few usual problems with pests or disease. PFAF does not flag the species as a weed.

All parts of hedge hyssop are poisonous. PFAF lists no known food uses for the plant. It has a history of use as a medicinal herb. Past uses included treatments for fluid retention and intestinal worms. PFAF considers those uses outdated because of the plant's toxicity. Reported harms include kidney damage, bowel bleeding, and pregnancy loss. Its medicinal history does not make it safe to use. Treat it as a poisonous garden plant, not an edible herb.