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sweet basil (Ocimum basilicum)

Ocimum basilicum is an upright, aromatic, highly branched herbaceous plant. Sources differ on its life cycle: it is commonly grown as an annual, may be a short-lived perennial in warm, tropical, or Mediterranean-type climates, and is also described by some sources as biennial.

LightFull sun in a bright, relatively sheltered position is preferred, although some sources also allow partial sun.
WaterSources differ on watering details, but describe maintaining moderate moisture with good drainage, allowing the surface soil to dry slightly before watering, and avoiding prolonged waterlogging.
HumidityA single source reports that Ocimum basilicum prefers high humidity.
TemperatureEvidence is limited to a single source, which reports an ideal temperature of about 18–27 °C, with about 7 °C at the low end and about 36 °C at the high end. A single source also reports a USDA hardiness-zone classificat
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Overview

Ocimum basilicum is an upright, aromatic, highly branched herbaceous plant. Sources differ on its life cycle: it is commonly grown as an annual, may be a short-lived perennial in warm, tropical, or Mediterranean-type climates, and is also described by some sources as biennial.

Origin and habitat

Sources differ on its native range: it is mainly described as native to tropical and subtropical Asia, from India and Sri Lanka eastward through Southeast Asia, southeastern China, and Taiwan to the Philippines, New Guinea, and northern Australia, while some sources also include Africa. It has long been cultivated by people, so its original natural habitat is unclear; it is also recorded from woodland, savanna, shrubland, natural grassland, and human-made environments. It is suited to tropical, subtropical, and warm environments and can be grown as an annual in warm-temperate climates; it prefers warmth and does not tolerate frost or cold.

Characteristics

Sources differ, with limited evidence, on mature size, reporting a height of about 30–150 cm and a spread of about 10–50 cm. The opposite leaves are usually green and ovate to elliptic, may be glossy or slightly wavy, and have margins ranging from smooth to slightly blunt-toothed; leaf size and shape vary markedly among cultivars. The small flowers are usually white but may be tinged pink, are tubular or lip-shaped, and occur in terminal spikes; flowering is mainly described as occurring through part of the year, with another account placing flower appearance in late summer. After pollination, the corolla falls and small nutlet-like fruits form within the calyx; another description characterizes the fruit as nearly elongated-spherical and black, and sources differ in their descriptions.

Light

Full sun in a bright, relatively sheltered position is preferred, although some sources also allow partial sun.

Watering

Sources differ on watering details, but describe maintaining moderate moisture with good drainage, allowing the surface soil to dry slightly before watering, and avoiding prolonged waterlogging.

Humidity and airflow

A single source reports that Ocimum basilicum prefers high humidity.

Temperature and dormancy

Evidence is limited to a single source, which reports an ideal temperature of about 18–27 °C, with about 7 °C at the low end and about 36 °C at the high end. A single source also reports a USDA hardiness-zone classification. Ocimum basilicum is frost tender; keep above freezing.

Growing medium and mounting

It prefers fertile, relatively light, well-drained soil and can grow in loam or sandy soil; sources also describe a preferred soil pH and a broader tolerated pH range.

Propagation

Ocimum basilicum can be propagated from seed and is also easy to transplant; in temperate regions it can be planted out after the last frost, while another recommendation describes warm sowing indoors or under glass in spring or direct sowing in summer.

Common problems

Potential pests include aphids, Japanese beetles, slugs, snails, and sage leafhoppers. A single source reports that basil downy mildew may occur. It is sensitive to low temperatures and frost and does not tolerate cold; in colder regions it is generally grown as an annual or overwintered in protected conditions such as indoors or in a greenhouse. Major cultivation problems mentioned by the sources include pests such as aphids, beetles, slugs, and snails, as well as basil downy mildew.

Identification

Distinguishing features include an aromatic scent, square stems, opposite leaves, and terminal spikes of small flowers. Genovese basil is explicitly listed as a cultivar of Ocimum basilicum, and in Western cooking the name basil commonly refers to Genovese basil or sweet basil.

Photos

Ocimum basilicum
📷 user:Risacher · CC BY-SA 3.0 · source
Ocimum basilicum
📷 Castielli · CC BY-SA 3.0 · source
Ocimum basilicum
📷 no rights reserved, uploaded by 葉子 · CC0 · source

Sources