Basil
Ocimum basilicum
By Rowan Plank · Published September 28, 2026
Sun
Full sun (6+ hrs); tolerates partial shade in hot climates
Water
~1 in/week, keep soil consistently moist
Spacing
12–18 in apart
Soil pH
6.0–7.5
Days to maturity
50–75 days from seed (baby leaves in ~30 days)
Hardiness zones
Grown as an annual in most zones; perennial only in 10–11
When to plant: After last frost, once daytime temps are in the 70s°F and nights stay above 50°F
Basil needs full sun, about 1 in of water a week, and warm weather — plant it only after nights stay above 50°F. Space plants 12–18 in apart and you can start harvesting in 50–75 days from seed, or pick baby leaves in about 30.
It's one of the easiest herbs to tuck into a vegetable bed, and it keeps producing all summer if you keep cutting it.
When should you plant basil?
Basil is cold-sensitive, so it goes in after your last frost — once daytime temperatures are consistently in the 70s°F and nights stay above 50°F. Cold soil and air stunt it, and leaves can blacken at around 50°F.
Sow seed ¼ in deep outdoors in late spring, or start seed indoors about 6 weeks before you plan to plant out. Space plants 12–18 in apart so air moves between them; crowded basil is more prone to disease.
Harvest often
Regular cutting is the single biggest thing you can do for basil — the more you cut, the more it branches and produces.
How do you keep basil from flowering?
Pinch out the growing tips once the plant has a few sets of leaves, and keep pinching off flower buds as soon as they appear. Letting basil flower changes the flavor of the leaves and slows new growth.
Which basil variety should you grow?
| Variety | Flavor | Best for |
|---|---|---|
| Genovese (sweet basil) | Classic sweet, clove-like | Pesto, tomatoes, Italian cooking |
| Thai | Anise / licorice | Asian dishes; holds up to heat |
| Lemon | Bright, citrusy | Fish, salads, tea |
| Purple (e.g. Dark Opal) | Similar to sweet basil | Color in beds and salads |
| Greek / dwarf bush | Mild, small leaves | Containers and bed edges |
Why is my basil struggling?
- Flowering early — heat stress or an older plant; pinch buds off right away.
- Downy mildew — grayish fuzz on leaf undersides in humid weather; give plants room and avoid overhead watering.
- Slow growth in containers — basil is a heavy feeder, and a nutrient-poor potting mix stalls it.
Basil pairs well in the same bed as tomatoes, which share its sun and water needs.
Sources: Basil — Penn State Extension, Basil — Illinois Extension.
Companion plants
Tomato, Peppers
FAQ
Why did my basil turn bitter and stop producing new leaves?
That's usually the plant switching to flowering, which heat and age both trigger. Pinch off flower buds as soon as you see them — once basil flowers, the leaf flavor suffers.
How should I harvest basil to keep it bushy?
Cut from the top, just above a pair of leaves, instead of picking single leaves from the bottom. The plant branches at the cut and grows fuller instead of tall and leggy.
Why are my basil leaves turning black?
Cold damage is the usual cause. Basil leaves can blacken when temperatures drop to around 50°F, so wait for warm nights before planting and cover or harvest plants before a cold snap.