Ocimum basilicum aka Sweet Basil

Basil is a warm-weather herb that is sensitive to cold — Swiss flora data rates it as a plant of warm sites, and it grows best in hot conditions. Seeds germinate fastest at roughly 34.5–39°C and need a minimum of about 10–13°C to germinate at all, so sowing into cold soil will stall the plant.

It is frost-tender and should never be exposed to freezing temperatures. Move it outdoors only after the last frost has passed, and bring pots back inside before the first autumn frost. Indoors, a warm, sun-facing windowsill kept away from cold drafts suits it best.

Basil's aroma comes mainly from linalool and methyl chavicol (estragole), present in roughly a 3:1 ratio, along with 1,8-cineole, eugenol and myrcene. The distinctive clove-like note in sweet basil is specifically down to its eugenol content.

Because the essential oil profile varies between named types, different basils smell noticeably different — lemon basil and cinnamon basil are named for exactly this reason.

Widely grown types include Genovese (classic sweet) basil, Thai basil (Ocimum basilicum var. thyrsiflorum), Greek or dwarf basil (var. minimum), purple basils such as 'Dark Opal' and 'Purpurescens', and Mrs Burns' Lemon (var. citriodora). Some familiar basils are actually interspecific hybrids: lemon basil is O. basilicum × O. americanum, and African blue basil is O. basilicum × O. kilimandscharicum.

If downy mildew is a problem in your area, look for resistant cultivars — trials rated 'Prospera' the overall favourite among mildew-resistant types, though it grows tall and can need staking to avoid stem breakage, and 'Rutgers Passion' also performed well.

Yes — basil grows best outdoors, and it is native to tropical Asia and Africa where it behaves as a perennial. Outside the tropics it is grown as a warm-season annual: plant out only after the last frost, in well-drained soil with direct sun and shelter from wind. NC State Extension recommends spacing plants roughly 12 inches to 3 feet apart. In the tropics it succeeds at elevations up to about 1,000 metres.

It is not frost-hardy, so in temperate regions the plant dies back with the first frost and is resown each year. Basil is non-native across Europe and North America and only rarely escapes cultivation — Go Botany notes that where it does appear outside gardens it is likely ephemeral, and Calflora documents only about ten scattered occurrence records in California.

Pinch off flower stems before they mature. Once a stem flowers it stops producing new leaves, so removing the buds keeps the plant in leaf production for much longer.

Regular harvesting is itself the best pruning: picking leaves prompts the plant to convert its topmost leaf pairs into new branching stems, giving a bushier, leafier plant. Pinching stem tips has the same effect.

Basil is easy to propagate both ways. From seed, sow in mid to late spring under cover and only just cover the seed — germination is usually quick and free, and is fastest in warm conditions. Soaking the seed for about 12 hours beforehand (hydropriming) improves germination. Prick seedlings out into individual pots and plant them outdoors only once the last frosts have passed.

It also roots readily from cuttings: take 5–10 cm non-lignified (soft, green) stem cuttings. Research has found that exposure to blue light accelerates root formation on basil cuttings.

Disease is the bigger threat. Fusarium wilt is a soil-borne fungus that can kill young plants quickly, Pythium causes damping-off in seedlings, and gray mold (Botrytis cinerea) affects plants in damp conditions. The most significant modern problem is basil downy mildew (Peronospora belbahrii), which spread through the eastern United States and into Canada by 2008; resistant cultivars such as 'Prospera' and 'Rutgers Passion' are the practical answer where it is established. Black spot (Colletotrichum spp.) also occurs.

Insect pressure is comparatively light — aphids and Japanese beetles are occasional problems. Basil's own essential oil actually repels thrips (Frankliniella occidentalis and Thrips tabaci), which is part of why it is valued as a companion plant.

Basil flowers are entomophilous (insect-pollinated) and are particularly attractive to bees, offering both nectar and pollen. The flowers are hermaphrodite — carrying both male and female organs — and the plant is self-fertile, so a single plant can set seed on its own.

After pollination the corolla drops away and four small round achenes (the seeds) develop inside the persistent calyx.

Yes — basil is the classic culinary herb of Mediterranean and Southeast Asian cooking, most famously as the base of Italian pesto. The leaves pair especially well with tomato, pasta, bean, pepper and aubergine dishes, and also make a refreshing tea. Cooking quickly destroys the flavour, often described as resembling liquorice, so leaves are usually added fresh or right at the end of cooking.

The flowers are edible too, used raw or cooked as a flavouring. The seeds become mucilaginous when soaked in water and are used this way in Asian drinks and desserts, including a beverage known as "sherbet tokhum". The essential oil is used commercially to flavour mustards, sauces and vinegars. PFAF gives basil an edibility rating of 4 out of 5.

Basil has a long history in folk medicine, including Ayurveda and traditional Chinese medicine, chiefly for the digestive and nervous systems — traditionally used to ease flatulence, stomach cramps, colic and indigestion, and also applied to feverish illness, nausea, migraine, insomnia and low mood. The leaves and flowering tops are described as antispasmodic, aromatic, carminative, digestive, galactagogue, stomachic and tonic. Externally it has been used for acne, insect stings, snake bites and skin infections.

Laboratory work supports some antimicrobial activity: basil essential oil shows antibacterial effects (for example against Lactiplantibacillus plantarum and Pseudomonas species) and antifungal activity against Aspergillus, Candida, Mucor and Geotrichum candidum. PFAF gives it a medicinal rating of 3 out of 5.

This reflects traditional use and preliminary research rather than clinical recommendation. Note also that basil essential oil contains estragole, which PFAF flags as potentially carcinogenic and mutagenic — it advises against use during pregnancy and against giving basil oil to infants or small children.

Basil's essential oil (yielding around 1.5% from the flowering tops) is used in perfumery and in dental preparations. Applied to the skin it acts as a mosquito repellent, and the growing or dried plant helps repel flies and greenhouse pests — research also credits the oil with insecticidal and nematicidal activity against several nematode species. Historically it served as a strewing herb.

The flowering tops can be used to make green and yellow dyes. Basil also carries religious significance in Greek, Bulgarian, Serbian, Macedonian and Romanian Orthodox traditions, where it is used in preparing holy water.

Sweet Basil presents a moderate level of care, which allows plant enthusiasts with some experience to expand their skills and knowledge.

Sweet Basil grows vertically and new growth emerges from the top of the plant.

Sweet Basil’s native range is Worldwide.

Sweet Basil should be watered regularly, allowing the soil to dry out between waterings.

Sweet Basil loves a well-draining soil. Perlite and vermiculite help with drainage, while coco coir adds organic matter, so a good potting soil mix will have all three. You can improve store-bought soil by adding some perlite to it.

Sweet Basil thrives in bright and direct sunlight. To ensure your plant receives enough light to survive, place it less than one foot from a window. The current weather in your area may affect the placement in your home. For example, if you live in a region that has longer and more intense periods of sunlight, then you may want to place the plant farther away from the window to avoid direct sunlight and reduce the risk of sunburn. Alternatively, if you live in a region with relatively milder temperatures and less intense sunlight, then you may be able to place the plant closer to the window for increased exposure. Ultimately, the current weather in your area should be taken into consideration when determining the best placement for your Thai Basil.

The Sweet Basil does not need extra humidity. Plants primarily absorb water through their root system, making soil watering the best way to provide humidity to your plants.

Sweet Basil is not known to cause harm to humans or pets.

During the wintertime, it's common for Sweet Basil to go dormant and their growth may slow down, so waterings should be spaced out more.

Yes, if you provide it with the correct amount of sunlight and water, you can witness your Sweet Basil blooming.