Sweet basil
Sources last read 14 September 2026.
Middling It gives warning, with time to act.
Also called Basil, common basil, Genovese Basil, Greek royal, kiss-me-Nicholas, lemon basil, Purple Basil, Saint Joseph's Wort and Thai Basil.
Toxicity is partly unassessed
What the sources say about its care
- Light
- Full sunRHS · read 13 September 2026
- Water
- Well-drainedRHS · read 13 September 2026
- Humidity
No source read publishes a humidity figure for any plant on this site. What follows is general guidance for foliage plants.
ASHRAE recommends indoor relative humidity between 30% and 60% 30–60%Penn State Extension · read 13 September 2026- Temperature
How cold this tolerates, not what it prefers. No source read for this site publishes a preferred range for a plant indoors.
H1C — 5–10°C 5–10 °CRHS · read 13 September 2026- Soil
- Loam, Sand; pH Acid or Alkaline or NeutralRHS · read 13 September 2026
- Toxic to cats
- Listed as non-toxicASPCA · read 13 September 2026
- Toxic to dogs
- Listed as non-toxicASPCA · read 13 September 2026
- Harmful to people
- No statement of harm to people is published for this plant; that absence is not evidence it is safe.RHS · read 13 September 2026
How it usually goes wrong
- A thin dry rim that crumbles between the fingers
Leaves on the side of the sweet basil nearest a heater or vent brown at the edges while those on the far side stay clean.
Dry air takes water from the leaf surface continuously, and the tissue at the edge is last in the queue for what the roots send up. Penn State Extension notes there is no single humidity figure that suits every indoor plant.
Telling it apart: When it started. Edges that browned as the heating came on point at air; edges that browned through a wet summer do not.
Penn State ExtensionSweet basil leggy, leaning growth: causes- Brown, papery patches on the leaves nearest the glass
On a sweet basil the marks are patchy and one-sided. Leaves on the shaded side of the crown keep their colour entirely.
Glass concentrates what would be tolerable outdoors, because it holds the heat and removes the moving air that carried it away. Its source describes full sun.
Telling it apart: Whether shaded parts are clean. Scorch follows the light exactly; a disease does not care where the sun fell.
RHSDiagnose brown tips and edges on this Sweet basil- The crown deflates, and lifts again within hours of a soak
Leaves on the sweet basil turn dull and soft before any colour changes, and water poured on the dry surface runs straight down the inside of the pot.
With well-drained soil taken past dry, there is nothing left for the roots to move, and the plant gives up its shape before it gives up its colour.
Telling it apart: Push a finger two inches in. Dry all the way down points at thirst; damp points somewhere else.
RHSDiagnose drooping on this Sweet basil
Not sure which it is? Ask the diagnosis questions for Sweet basil.
Routine care
- Propagation
- Seed, stem cuttingsNC State Extension · read 13 September 2026In spring sow seed under glass or indoors with gentle heat, or sow where it is to grow in summer. Sowing seeds indoors has more guidance.RHS · read 13 September 2026
- Pruning
- Pinch out flower buds and the ends of long stems.NC State Extension · read 13 September 2026Pinch off flowerheads when they appear to promote more leaf growth.RHS · read 13 September 2026
- Pests and diseases
- Can be troubled by Japanese beetle, aphids, and slugs and snails. Diseases: basil downy mildew.NC State Extension · read 13 September 2026Can be troubled by sage leafhopper, snails, slugs and aphids. Diseases: powdery mildews can occur.RHS · read 13 September 2026
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About the plant
Basil, also called great basil, is a culinary herb of the family Lamiaceae (mints). It is a tender plant and is used in cuisines worldwide. In Western cuisine, the generic term "basil" refers to the variety also known as Genovese basil or sweet basil. Basil is native to tropical regions from Central Africa to Southeast Asia. In temperate climates basil is treated as an annual plant, but it can be grown as a short-lived perennial or biennial in warmer horticultural zones with tropical or Mediterranean climates.
From Wikipedia, CC BY-SA 4.0 · read 13 September 2026
- Native range
- Trop. & Subtrop. Asia to N. AustraliaWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026Tropical Africa and AsiaNC State Extension · read 13 September 2026
- Climate
- seasonally dry tropicalWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026
- Growth form
- annual or subshrubWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026Annual, Herb, Herbaceous Perennial; habit ascendingNC State Extension · read 13 September 2026Bushy (deciduous)RHS · read 13 September 2026
- Size
- Height 4–36 in; width 4–14 inNC State Extension · read 13 September 2026Height 0.1-0.5 metres; spread 0.1-0.5 metres after 1–2 yearsRHS · read 13 September 2026
- Flowering
- Flowers pink, purple/lavender, white; blooms in summerNC State Extension · read 13 September 2026Flowers pink in summer; white in summerRHS · read 13 September 2026
- Uses
What sources record people using this plant for. A traditional or medicinal use listed here is a record of use, not advice to eat it or treat anything with it.
The tops of the plant yield yellow and green dyes. Leaves and flowers are used in tea and for flavoring.NC State Extension · read 13 September 2026
Common problems with Sweet basil
More of the Lamiaceae family
English lavenderBuds form and fall before they open
RosemaryCrisp margins that appear in winter
Caribbean OreganoSourced care, difficulty not yet judged
ColeusSourced care, difficulty not yet judged
- No photograph yetColeus thyrsoideusSourced care, difficulty not yet judged
Plectranthus oertendahliiSourced care, difficulty not yet judged
Plants with similar care
Sources
- ASPCA · read 13 September 2026
- Kew WCVP · read 13 September 2026
- NC State Extension · read 13 September 2026
- Penn State Extension · read 13 September 2026
- RHS · read 13 September 2026
- Wikipedia · read 13 September 2026
What this does not cover
The figures above are what published sources say, not measurements of the plant in your room. They say nothing about your pot size, your water, the season, or how far from the glass the plant stands, and those decide more than any figure here does.
Humidity has no species figure because no source read for this site publishes one, and the only temperature published for this plant is a cold floor. The simulator fills those gaps with general figures for its kind of plant, marked as general and listed on how we read sources. Where a toxicity row says the plant was not assessed, that is the absence of a finding and not a finding of safety.
If something is already wrong, the diagnosis tool asks about the soil, the window and the watering, which is where the answer usually is.