Prunella vulgaris, known as common selfheal, heal-all, heart-of-the-earth or h kh tho in Vietnamese, is a medicinal plant in the genus Prunella. It grows from 1 to 2 feet high, with creeping, self-rooting, tough, square, reddish stems branching at leaf axis. The leaves are lance shaped, serrated and reddish at tip, about an inch long and 1/2 inch broad, grow on short stalks in opposite pairs down the square stem. The flowers grow from a clublike, somewhat square, whirled cluster, immediately below this club are a pair of stalkless leaves standing out on either side like a collar. Flowers are two lipped and tubular, the top lip is a purple hood, and the bottom lip is often white, it has three lobes with the middle lobe being larger and fringed upwardly. Flowers bloom at different times depending on climate and other conditions; Mostly from June to August. For medicinal purposes, the whole plant is gathered when the flowers bloom, and dried. The leaves and small flowers of heal-all are edible. Heal-all is a perennial herb found throughout Europe, Asia, Japan and the United States of America, as well as most temperate climates. Its origin seems to be European, though it has been documented in other countries since before any history of travel. In the United Kingdom it is abundant throughout Wales, Scotland, Northern Ireland and England. In the Republic of Ireland it is currently abundant in the west in counties Galway and Clare, the south-west in Kerry, the south coast and is also found around the central basin of Ireland. It is often found growing in waste ground, grassland, woodland edges, usually on basic and neutral soils. It is grown in any damp soil in full sun or in light shade. Seeds are sown in very early spring in a flat outdoor area.
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