Holy basil is an erect, many-branched subshrub, 30–60 cm (12–24 in) tall with hairy stems. Leaves are green or purple; they are simple, petioled, with an ovate, up to 5 cm (2.0 in)-long blade which usually has a slightly toothed margin; they are strongly scented and have a decussatephyllotaxy. The purplish flowers are placed in close whorls on elongate racemes.
The three main morphotypes cultivated in India and Nepal are Ram tulsi (the most common type, with broad bright green leaves that are slightly sweet leaves), the less common purplish green-leaved (Krishnatulasi) and the rare wild "vana tulsi".
The ritual lighting of lamps each evening during Kartik includes the worship of the tulsi plant, which is held to be auspicious for the home.Vaishnavas traditionally use Hindu prayer beads made from tulsi stems or roots, which are an important symbol of initiation. They have such a strong association with Vaishnavas, that followers of Vishnu are known as "those who bear the tulsi round the neck".
Tulasi (Sanskrit:-Surasa) has been used in Ayurveda and Siddha practices for its supposed treatment of diseases.
Phat kaphrao mu – Thai holy basil with pork – a common dish in Thailand
The leaves of holy basil, known as kaphrao in the Thai language (Thai: กะเพรา), are commonly used in Thai cuisine for certain stir-fries and curries such as phat kaphrao (Thai: ผัดกะเพรา) — a stir-fry of Thai holy basil with meats, seafood or, as in khao phat kraphao, with rice. Two different types of holy basil are used in Thailand, a "red" variant which tends to be more pungent, and a "white" version for seafood dishes.Kaphrao should not be confused with horapha (Thai: โหระพา), which is normally known as Thai basil, or with Thai lemon basil (maenglak; Thai: แมงลัก).
For centuries, the dried leaves have been mixed with stored grains to repel insects.
The genome of Tulsi plant has been sequenced and reported as a draft, estimated to be 612 mega bases, with results showing genes for biosynthesis of anthocyanins in Shyama Tulsi, ursolic acid and eugenol in Rama Tulsi.
O. tenuiflorum in India
Tulsi grown in a home garden
An altar with tulsi plant for daily worship in a courtyard in India
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