Basil is the herb no summer garden should be without: the sweet, peppery leaf behind pesto, caprese salads and a hundred tomato dishes, and one of the easiest herbs to grow well — as long as it gets what it wants, which is heat, sun and regular picking. A basil plant that is pinched often becomes a bushy, productive plant; one that is left alone goes to flower and stops producing leaves.
Basil is a tender annual that matures in 60–70 days, and it will not tolerate frost or cold soil at all — it is the last herb to go outside in spring and the first to die in autumn. That tenderness is the whole story of growing it: start it indoors, plant it out when it is truly warm, and pick it constantly. This guide covers starting, pinching for bushy growth, watering, and harvesting for the biggest, most flavourful leaves.
Basil at a glance
| Growing factor | What this crop needs |
|---|---|
| Sun | full sun |
| Soil pH | 6.0–7.5 |
| Days to germination | 5–10 |
| Days to maturity | 60–70 |
| Spacing | 12–18 inches |
| Water needs | moderate |
| Cold tolerance | tender |
| Family | Lamiaceae |
Starting seeds
Basil seed is best started indoors. Sow in trays or modules filled with fine seed compost, barely covering the seed, and keep the tray warm and moist — germination takes 5–10 days. Give seedlings as much light as you can once they appear. Our seed-starting calculator can work out your sowing date from your last frost, and the germination-time calculator helps you plan around the 5–10-day germination window.
Because this is a tender crop, timing follows the frost: in Zones 3–6 start indoors and plant out only once frosts are past and the soil has warmed; in Zones 7–9 the warm season is long and a second sowing is often possible; in Zones 10–13, which are frost-free, grow it through the cooler months with afternoon shade in the hottest weather. Check your dates with our frost-date calculator or the last-first frost lookup — and when in doubt, ask your local extension service.
Start basil indoors — it germinates in 5–10 days in warm conditions, and it needs warmth from the start. Sow thinly on the surface of fine compost, barely covering the seed, and keep the tray warm: cold compost is the commonest reason basil seed fails.
Transplanting and planting out
Harden seedlings off for a week before planting out: put them outside for a few hours a day, increasing the time and exposure, and bring them back in at night. Plant out at the final spacing of 12–18 inches apart, in holes the same depth as the pot. Water each plant in well and mulch around (not against) the stems to hold moisture. Our plant-spacing calculator shows how many plants fit your bed at 12–18-inch spacing.
Soil and feeding
Basil grows best in soil with a pH of 6.0–7.5, so test your soil before you plant — a cheap test kit tells you more than guessing ever will. Work in a little compost to improve structure, but keep the soil lean — herbs prefer soil that is not over-rich — and make sure the bed drains freely. Our soil-volume calculator and raised-bed soil calculator work out how much soil or compost your bed needs.
Feed lightly: herbs grown in soil that is too rich produce lots of soft leaf with diluted flavour. A little compost at planting time is usually enough, with at most a light feed in spring. Our fertiliser calculator works out how much to apply if your soil is genuinely poor.
Basil likes rich, well-drained soil with a pH of 6.0–7.5. Dig in compost before planting and feed lightly every couple of weeks once plants are growing — hungry basil grows fast and flavourful.
Watering
Water evenly and avoid letting the soil swing between soaked and bone dry. A deep soak once or twice a week beats a daily sprinkle, because it encourages roots to grow down where the soil stays cooler and moister. Mulch helps enormously here, holding moisture and keeping the soil temperature steady. Our watering calculator gives a starting point for your bed size and soil, and the watering schedule generator can build a routine around it.
Sunlight and temperature
Give Basil full sun — at least six hours of direct sun a day, and more is better in most zones. Sun drives flavour and yield in this crop, and plants in shade stay leggy and unproductive. Our sunlight calculator can check whether your spot gets enough sun.
It is tender, so cold is the enemy: a single frost can finish it. Wait until frosts are past and the soil feels warm before planting out, and keep fleece or cloches handy for a late cold snap. In warm zones it will keep producing until the first cold nights of autumn.
Pests and diseases
The pests and diseases to watch for with Basil are aphids, slugs and whiteflies.
Aphids cluster on tender new growth and under leaves, sucking sap and leaving sticky honeydew.
Slugs and snails chew ragged holes in leaves at night and love damp, mulched beds.
Whiteflies cloud up from the undersides of leaves when disturbed.
Prevention beats cure: rotate crops so the same family does not grow in the same bed year after year, clear debris at the end of the season, and inspect the undersides of leaves weekly. Our pest identifier helper can help you name a pest from its damage, and the plant-disease checker can narrow down a leaf problem.
Companion plants
Good companions for Basil are tomatoes, peppers, oregano, marigolds and asparagus.
Tomatoes share this plant's love of sun and rich soil, and the pairing works well when both get enough space and airflow.
Peppers enjoy the same warm, sunny bed and similar watering, so they make a natural neighbour.
Oregano's strong scent is thought to confuse pests, and as a low spreader it works well as a living edge around taller herbs.
Marigolds are the classic companion: their roots and scent deter several soil pests, and their flowers bring in pollinators and beneficial insects.
Asparagus is a long-lived perennial that pairs well here, and the two crops occupy different root zones.
Plant companions in the same bed rather than in a separate corner — that is how they do their work. Our companion-planting finder can suggest more pairings for your bed.
Harvesting
Basil is ready to harvest about 60–70 days after sowing, but start picking much sooner — once plants have six or eight pairs of leaves, pinch the tips regularly. Always pick from the top, pinching just above a pair of leaves: the plant branches from that point and becomes bushier with every picking. Never strip a plant bare — take a third at most, and it will regrow within a week or two.
Harvest in the morning, when the essential oils are at their strongest, and use the leaves fresh — basil loses flavour fast once picked. If flower buds appear, pinch them off at once: once basil flowers, the leaves turn bitter and the plant stops producing. At the end of the season, before the first frost, pick everything and make pesto, which freezes beautifully. Basil does not dry well, so pesto or freezing in oil is the way to keep it.
Common problems and fixes
| Problem | Likely cause | Fix |
|---|---|---|
| Leaves turn yellow | cold, wet soil or overwatering | Let the soil dry between waterings and give the plant warmth and sun. |
| Plant bolts and flowers early | stress, usually heat or drought | Pinch flowers off at once and water evenly; pick regularly. |
| Black spots on leaves | downy mildew or cold damage | Improve airflow, water at the base, and remove affected leaves. |
Leaves turn yellow
Likely cause: cold, wet soil or overwatering. Yellow basil leaves usually mean the plant is cold or its roots are too wet. Basil hates cold soil and waterlogged compost — check drainage, let the pot or bed dry out between waterings, and move potted plants to the warmest spot.
Plant bolts and flowers early
Likely cause: stress, usually heat or drought. Basil flowers when it is stressed — usually by heat, drought or being left unpicked. Pinch flower buds off as soon as you see them, keep watering even, and pick the tips regularly: a plant that is picked often stays leafy far longer than one left alone.
Black spots on leaves
Likely cause: downy mildew or cold damage. Black or grey spots on basil leaves are often downy mildew, which thrives in damp, still air, or cold damage after a chilly night. Remove affected leaves, water only at the base, space plants for airflow, and do not let the plant get cold.
Frequently asked questions
How long does basil take to grow?
Basil takes 60–70 days from sowing to full size, but you can start picking leaves much sooner — once the plant has six or eight pairs of leaves. Regular picking keeps it producing all summer until the first frost.
Should I pinch basil flowers off?
Yes — pinch flower buds off as soon as you see them. Once basil flowers, the leaves turn bitter and the plant stops producing new leaves.
Can basil grow indoors?
Yes — basil is one of the best herbs for a sunny windowsill, as long as it gets at least six hours of direct sun or a grow light. Use a pot with drainage, water when the top of the compost dries, and pinch the tips regularly to keep it bushy.
Why is my basil turning yellow?
Yellow leaves usually mean cold or wet roots. Basil needs warmth and good drainage — check that the pot or bed drains freely, let the soil dry between waterings, and keep the plant in the warmest, sunniest spot you have.