Growing Basil in the Home Garden
Basil (Ocimum basilicum) is a tender annual in the mint family, grown for its leaves. It is easy from seed, but it hates cold: a few nights in the 40s will blacken the leaves and stall the plant. Get the timing right and keep pinching, and one plant will give you leaves from early summer until the first frost.
Varieties
| Type | What to expect |
|---|---|
| Genovese (sweet basil) | Large, cupped leaves; the standard for pesto and tomato dishes |
| Thai basil | Smaller leaves, purple stems and an anise-clove flavor; holds up better in heat and in cooking |
| Lemon and lime basil | Narrow leaves with a citrus scent; good with fish and in drinks |
| Purple basil ('Dark Opal', 'Purple Ruffles') | Same flavor family as sweet basil, grown as much for color |
| Greek or globe basil ('Spicy Globe') | Tiny leaves on a compact mound; suits pots and edging |
| Holy basil, or tulsi (Ocimum tenuiflorum) | A separate species, sacred in Hinduism, with a clove-like scent; mostly used for tea |
If downy mildew has hit your basil before (see below), grow a resistant variety such as 'Prospera' or one of the Rutgers releases ('Devotion', 'Obsession', 'Passion').
When to plant
Basil goes outside at the same time as tomatoes: one to two weeks after your last frost date, once nights stay above 50°F. Look up your frost dates with the zone and frost date lookup.
- Starting indoors: sow about six weeks before your last frost date, 1/4 inch deep. Seeds sprout in about a week at 70°F or warmer; a heat mat helps in a cool house.
- Direct sowing: wait until the soil has warmed to about 70°F. Seed sown into cold soil sits there or rots.
- Buying plants: the pots of basil sold at grocery stores are usually a dozen or more seedlings crowded together. Tease them apart and plant them separately, or plant small clumps.
Site, soil and spacing
Give basil full sun, at least six to eight hours, and fertile, well-drained soil with some compost worked in. A pH of 6.0 to 7.5 is fine. Space plants 12 to 18 inches apart; the wider spacing suits large Genovese types and helps air move between plants, which matters for disease.
Basil does well in containers, but a small pot in full sun dries out fast in July. Use a pot at least 8 inches across and check it daily in hot weather.
Water at the base so the soil stays evenly moist but not soggy, and mulch once the soil is warm. A side-dressing of compost in midsummer keeps plants producing after heavy picking.
Pinching and harvesting
When a plant has three pairs of true leaves, cut the main stem just above the second pair. Two new shoots grow from that point, and repeating this every few weeks turns one stem into a bushy plant.
Pinch off flower spikes as soon as they appear. Once basil flowers freely, it puts out fewer new leaves and the leaves get tougher and less sweet. If you fall behind, cut the whole plant back by about a third, just above a pair of leaves, and it will regrow.
Harvest by cutting stem tips above a leaf pair rather than stripping single leaves, and never take more than about a third of the plant at once. Basil does not survive frost, so pick everything when one is forecast.
Pests and diseases
- Downy mildew is the most serious basil problem in the US. Leaves yellow, usually starting near the center vein, and the undersides show a gray-purple fuzz. It spreads fast in humid weather and on infected transplants. Pull infected plants, space plants widely, water in the morning, and choose resistant varieties.
- Fusarium wilt causes stunting, wilting and brown streaks on stems. It lives in the soil, so don't replant basil in the same spot, and buy seed from a reputable source.
- Japanese beetles skeletonize leaves in midsummer. Knock them into a bucket of soapy water in the morning. See the Japanese beetle guide.
- Slugs chew holes in lower leaves, especially in mulched, damp beds.
- Aphids cluster on new growth; a strong spray of water usually takes care of them.
Storing basil
Don't put fresh basil in the refrigerator; temperatures below about 50°F turn the leaves black. Stand cut stems in a glass of water on the counter, like flowers, and they will keep for several days. For longer storage, purée leaves with a little olive oil and freeze the paste in ice cube trays, or freeze pesto without the cheese. Dried basil loses most of its flavor.
For other herbs to grow alongside it, see Growing Herbs in the Home Garden.