Ocimum tenuifolium (known as Holy basil in English, and Tulasi in Sanskrit), is a well known aromatic plant in the family Lamiaceae. Apart from its culinary uses, for which it is known across the world, it is also used as a medicinal plant, and has an important role within many traditions of Hinduism, wherein devotees perform worship involving Tulasi plants or leaves. Native to India, it is a short lived perennial herb or small shrub, often grown as an annual. The foliage is green or purple, strongly scented. Leaves have petioles, and are ovate, up to 5cm long, usually somewhat toothed. Flowers are white, tinged purple, borne in racemes.
Its aroma is distinctively different from its close cousin, the Thai Basil which is sometimes wrongly called Holy Basil, in shops and on the internet, but they can be distinguished by their aroma and flavour. Holy Basil is slightly hairy, whereas Thai Basil is smooth and hairless; Holy Basil does not have the strong aniseed or licorice smell of Thai Basil; and Holy Basil has a spicy flavor sometimes compared to cloves.
 Sacred basil or Tulasi
Known as Tulasi (alternate spelling Tulsi) in India it is an important symbol in many Hindu religious traditions which link the plant with the Goddess figure described in the Puranas. The name "Tulasi" in sanskrit means "the incomparable one". The Tulasi plant is known in India in two forms - dark or Shyama (Krishna) Tulasi and light or Rama Tulasi. The former possesses greater medicinal value and is commonly used for worship.
Tulasi has also been known for thousands of years as a prime herb in Ayurvedic treatment, for its diverse healing properties. It is mentioned by Charaka in the Charaka Samhita, the central teaching of Ayurvedic medicine, and in the Rigveda. Tulasi is considered to be an adaptogen, balancing different processes in the body, and helpful for adapting to stress. Marked by its strong aroma and astringent taste, it is regarded as a kind of "elixir of life" and believed to promote longevity.
 Tulasi as an Ayurvedic medicine
Tulasi’s extracts are used in ayurvedic remedies for common colds, headaches, stomach disorders, inflammation, heart disease, various forms of poisoning, and malaria. Traditionally, tulasi is taken in many forms: as an herbal tea, dried powder, fresh leaf, or mixed with ghee. Essential oil extracted from Karpoora Tulsi is mostly used for medicinal purposes and in herbal toiletry. For centuries, the dried leaves of Tulasi have been mixed with stored grains to repel insects.
Recent studies suggest that Tulasi may be a COX-2 inhibitor, like many modern painkillers, due to its significant amount of Eugenol (1-hydroxy-2-methoxy-4-allylbenzene). Studies have also shown Tulsi to be effective for diabetes, by reducing blood glucose levels. The same study showed significant reduction in total cholesterol levels with Tulsi. Another study showed that Tulsi's beneficial effect on blood glucose levels is due to its antioxidant properties.
Tulasi also shows some promise for protection from radiation poisoning and cataracts. Some Vaishnavites do not use Tulasi for medicine, though, out of reverence. However, the use of Tulsi for purification and as a medicine is widespread throughout India. Many Hindus — along with the ancient tradition of Ayurveda — believe that the healing properties of sacred herbs such as Tulsi were given by the Lord himself, and can be used as a medicine out of reverence.
 Tulasi in scripture
A number of passages in the Puranas and other scriptures (Vedas), point to the importance of tulsi within religious worship. Tulasi is regarded as a goddess (Lakshmi) and a consort of Vishnu. A garland of tulasi leaves is the first offering to the Lord as part of the daily ritual. Tulsi is accorded the sixth place among the eight objects of worship in the ritual of the consecration of the kalasha, the container of holy water.
According to one story, Tulasi was a gopi who fell in love with Krishna and so had a curse laid on her by His consort Radha. She is very dear to Vishnu. Tulsi is also mentioned in the stories of Mira and Radha immortalised in Jayadeva's Gita Govinda. One story has it that when Krishna was weighed in gold, not even all the ornaments of His consort Satyabhama could outweigh Him. But a single tulsi leaf placed on one side by his consort Rukmini tilted the scale.
Tulsi is ceremonially married to Vishnu annually on the eleventh bright day of the month of Kaartika in the lunisolar calendar. This festival continues for five days and concludes on the full moon day, which falls in mid-October. This ritual, called the "Tulsi Vivaha", inaugurates the annual marriage season in India.
 Quotes regarding Tulasi
 Tulasi as a deity
The presence of a Tulsi plant symbolizes the religious bent of a Hindu family. In many traditions (i.e Vaishnavism), a household is considered incomplete if it doesn't have a Tulasi plant. Many families have the Tulasi planted in a specially built structure, which has images of deities installed on all four sides, and an alcove for small earthen oil lamp. Some households can even have up to a dozen Tulasi plants on the verandah or in the garden forming a "Tulsi-van" or "Tulsivrindavan" — a miniature basil forest.
Places that tend to inspire concentration and places ideal for worship, according to the Gandharva tantra, include "grounds overgrown with Tulsi plants". The Tulsi Manas Mandir at Varanasi is one such famous temple, where Tulasi is worshipped along with other devas (demi-gods/goddesses). Vaishnavites, or followers of Vishnu, revere the Tulasi leaf because it pleases Vishnu the most and thus is as an inherent part of offerings of naivedya. They also wear beaded necklaces made of Tulasi stems. The manufacture of these Tulasi necklaces is a cottage industry in places of pilgrimage and temple towns. Another name for Tulsi within the Gaudiya Vaishnava tradition is Vrindadevi, meaning 'the goddess of Vrindavan'.
 Tulasi Puja
Followers of Hindu traditions often keep a Tulsi plant in front of their house. On a specific day each year known as 'Kartik Shukla Dwadashi' (usually about two weeks after Diwali) there is a tradition wherein Tulasi plants will be beautifully decorated with structures made of sugarcane, mango leaves and flowers and then a puja (form of worship) is offered.
As with Diwali celebrations there are usually clay lamps lit around the Tulasi plant and the house. In some parts of India people will have also have fireworks displays to mark the occasion. In northern India and in Gaudiya Vaishnava communities it is called the 'Tulsi vivah' or the wedding day of Tulasi with Krishna in his Sila form. There is another celebration called Tulsi Ekadashi where Tulasi is worshipped on the Ekadasi day.