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Plant care

Basil care

Ocimum basilicum

Also called sweet basil, Genovese basil.

RHS H1cUSDA Grown as an annual in zones 4-11Pet-safeIndoor 30-60 cm tall

Watering rhythm

1-2days

When the top 1 cm of soil is dry, often every 1-2 days in summer

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Light

Direct sun (at least 4-6 hours)

Soil

Rich free-draining potting compost or garden loam

Humidity

40-60% (outdoor)

Temp

18-30°C

Pet safety

Pet-safe

Mature size

30-60 cm tall

Care at a glance

Light

Most houseplants will scorch where basil thrives. Give it the windowsill you'd otherwise leave empty because everything else burned there. 6+ hours of direct sun or a strong grow light indoors. Low light produces leggy plants with weak flavour. A plant moved abruptly from low light to direct sun bleaches in 48 hours — always acclimatise over a week.

Watering

Aim for when the top 1 cm of soil is dry, often every 1-2 days in summer for basil, but treat that as a starting point rather than a rule. A south-facing summer windowsill will dry the pot twice as fast as a north-facing winter room. Lift the pot; if it feels noticeably lighter than it did wet, water it. Basil wilts dramatically when dry but recovers quickly with water. Avoid wetting leaves at evening to prevent fungal disease.

Soil and pot

Basil grows best in rich free-draining potting compost or garden loam. Standard potting compost or compost-amended garden soil; pH 6.0-7.5. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Basil sits happiest at around 40-60% (outdoor) humidity and 18-30°C (65-85°F). Average outdoor humidity is fine. If you keep the room above 18 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed basil sparingly. Half-strength balanced liquid feed every 2-3 weeks during the growing season; nothing fancy needed. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on basil in the Growli community. Where a problem matches one of our diagnostic guides, click through for the full step-by-step recovery plan written for basil specifically.

  • Yellow lower leaves — Overwatering, nitrogen depletion, or downy mildew.
  • Curling leaves — Heat stress, aphids, or thrips.
  • Brown leaf spots — Bacterial leaf spot or downy mildew — water at the soil line.
  • Drooping leaves — Either underwatering or fusarium wilt; check soil moisture first.
  • Bolting (flowering) — Pinch flower buds the moment you see them to extend leaf production.

Companion plants

Basil pairs well with Tomato, Pepper, and Marigold. These are species with similar light and water needs, so you can grow them in the same bed or container without conflict.

Propagation

Direct-sow seed after the last spring frost, or root tip cuttings in water in a week. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Basil is pet-safe. ASPCA lists Ocimum basilicum as non-toxic to cats and dogs. Safe to grow on the kitchen windowsill. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Basil care — frequently asked questions

What is Basil?

Basil (Ocimum basilicum) is a culinary herb with a bushy upright annual growth habit, reaching 30-60 cm tall at maturity. Basil is a fast-growing warm-season annual herb from tropical Asia and the classic Italian kitchen herb. It rewards regular pinching with bushy plants and bolts quickly when stressed.

How much light does basil need?

Basil grows best in direct sun (at least 4-6 hours). 6+ hours of direct sun or a strong grow light indoors. Low light produces leggy plants with weak flavour.

How often should I water basil?

Water basil when the top 1 cm of soil is dry, often every 1-2 days in summer. Basil wilts dramatically when dry but recovers quickly with water. Avoid wetting leaves at evening to prevent fungal disease. The finger-test (or lifting the pot to feel its weight) beats a fixed weekly calendar because pot size, light, and season all change how fast the soil dries.

Is basil toxic to cats and dogs?

Basil is pet-safe. ASPCA lists Ocimum basilicum as non-toxic to cats and dogs. Safe to grow on the kitchen windowsill.

What USDA hardiness zone does basil grow in?

Basil is rated for USDA zone Grown as an annual in zones 4-11 and RHS hardiness H1c. Outside that range, grow it as a container plant that overwinters indoors before the first hard frost.

Basil deep-dive guides

Every aspect of basil care, each with its own calibrated guide:

Related guides

Basil is also commonly called sweet basil or Genovese basil.