Overview
What basil needs, when to pick it, and whether it suits your garden or windowsill.
Basil is a tender plant from warm climates, and cold checks it: frost kills it outright. Give it warmth and sun, though, and it grows fast, and every time you pick a shoot tip it branches. Beyond sweet basil there is Thai, lemon, cinnamon, purple and holy basil, and a crowded supermarket pot, split up, becomes a summer’s worth of plants.
Quick facts
- Botanical name
- Ocimum basilicum
- Feeding
- Light feeder
- Hardiness
- Any zone, as an annual
- Height
- Up to 60 cm (24 in)
- Propagation
- Seed, Cutting
Keep above 10 °C
Growing details
- Spacing
- 25 cm (10 in)
- Frost sensitivity
- Frost tender
Growing calendar
- Start indoors: 4 to 6 weeks before your last frost
- Plant out: May, June
- Harvest: June, July, August, September
Once nights stay above 10 °C (50 °F) and the soil has warmed. Outdoors in a cool temperate summer; longer under glass or on a sunny windowsill.
Is this plant right for you?
- Container friendly
- Windowsill friendly
- Greenhouse friendly
- Beginner friendly
- Needs warmth
- Frost tender
- Pet safe
- Grow with tomatoes
Good to know
Keep it above 10 °C (50 °F): frost kills it. It does well in a pot indoors or out, so you do not need a bed for it.
Before You Grow
Choose a type for your kitchen, then find the warmest, most sheltered sunny spot you have.
Sweet ‘Genovese’ is the pesto basil, but it is among the most prone to downy mildew.
What you need
Seed or young plants
Seed gives the widest choice. A supermarket pot works too, once split up. See rescuing supermarket basil.
Seed compost and small pots
Modules or 7.5 cm (3 in) pots, and a propagator or a clear bag.
Your warmest, sunniest spot
A greenhouse, a sunny windowsill, or a sheltered patio. See where it grows best.
A container at least 20 cm (8 in) wide
Basil does best in pots. See basil in containers.
Scissors
For picking just above a pair of leaves.
Choose your basil
There are about 150 basil species and many varieties, from sweet basil to spicy Thai, lemon, lime, cinnamon and holy basil. Most make compact plants 20 to 50 cm (8 to 20 in) tall.
Sweet basil is the everyday one, and ‘Genovese’ is the classic Italian strain for pesto. Large-leaved types such as ‘Napoletano’ suit salads; compact bush or Greek basil, with tiny pungent leaves, suits pots and edging.
Purple basils such as ‘Dark Opal’, ‘Red Rubin’ and ‘Crimson King’ are as decorative as they are edible.
Downy mildew changes the choice. Where this disease is a problem, look for varieties with ‘DMR’ in the name, or bred for resistance such as ‘Obsession’, ‘Devotion’, ‘Prospera’, ‘Amazel’ and ‘Eleonora’. Green sweet basils, ‘Genovese’ especially, are the most susceptible; purple, Thai, lemon and spice basils less so.
Seed or plants. Seed gives the widest choice. Plug plants and supermarket pots are quicker, but supermarket pots are crowded and need splitting to last.
Basil types compared
-
Sweet (‘Genovese’)
- Flavour
- Sweet, classic
- Habit
- Upright, up to 60 cm (2 ft)
- Use
- Pesto, tomato dishes
- Downy mildew
- Very susceptible
-
Large-leaved (‘Napoletano’)
- Flavour
- Milder
- Habit
- Big, wide leaves
- Use
- Salads, sauces
- Downy mildew
- Susceptible
-
Greek or bush
- Flavour
- Pungent, anise-clove
- Habit
- Compact, tiny leaves
- Use
- Pots, edging, pesto
- Downy mildew
- Susceptible
-
Purple (‘Dark Opal’, ‘Red Rubin’)
- Flavour
- Less sweet
- Habit
- Up to 45 cm (18 in)
- Use
- Salads, vinegars, colour
- Downy mildew
- Less susceptible
-
Thai
- Flavour
- Sweet anise, spicy
- Habit
- Purple stems, narrow leaves
- Use
- Thai and Asian cooking
- Downy mildew
- Less susceptible
-
Lemon and lime
- Flavour
- Citrus
- Habit
- Compact
- Use
- Fish, desserts, sorbets
- Downy mildew
- Less susceptible
For pesto, sweet basil; where downy mildew strikes, a resistant variety or a purple, Thai or lemon basil.
Where basil grows best
Basil is a tender herb that needs warmth. It is readily damaged by frost and dislikes cold, damp conditions.
Outdoors, it wants the warmest, most sheltered sunny spot you have, protected from wind and cold air. For when to plant out, see when to sow and plant.
Under cover is the most reliable way in cooler climates: a greenhouse, polytunnel or warm, bright windowsill gives a longer season, from spring to mid-autumn. Ventilate a greenhouse well to keep fungal disease down.
Air. Space plants so air moves between them; crowded, humid basil invites disease.
Sun. Give basil full sun: at least six hours of direct sun a day, and Penn State asks for six to eight.
Midday scorch. Gardeners’ World prefers plenty of light but not too much fierce midday sun, which can scorch the leaves a little. Tomatoes planted alongside cast useful light shade at the hottest time of day.
Seedlings need bright light as soon as they come up; in poor light they grow lanky and transplant badly. That is why seed is best started on a bright windowsill.
Indoors, a sunny window works, though indoor basil has a less intense flavour and fragrance.
- Frost
- Damages or kills it
- Best under cover
- Greenhouse, polytunnel or sunny windowsill
Soil and compost
Basil wants fertile soil that stays moist but drains freely: it suffers in wet ground, and hates wet roots overnight.
In pots, use peat-free multi-purpose compost; Gardeners’ World mixes in soil-based compost for potted-on plants.
In the ground, choose a well-drained spot. On heavy or wet soil, grow it in containers instead, where slugs are simpler to keep off.
Hold back the nitrogen. See feeding.
Planting
Sow indoors in warmth, harden plants off gently, and plant out once nights stay above 10 °C (50 °F).
Sow a small batch every few weeks from spring to summer for a steady supply.
When to sow and plant basil
Basil is all about warmth, so time it by temperature rather than the calendar.
Sow indoors four to six weeks before your last frost (Iowa State says four or five, Penn State six). The RHS sows from March through to July; sowing small batches a few weeks apart spreads the harvest.
Plant out after your last frost, once nights stay above 10 °C (50 °F) and the soil has warmed to at least 16 °C (60 °F): early summer in the UK.
Sow outdoors only in warm areas, in early summer once nights are consistently above 10 °C (50 °F). Sow thinly into warm, free-draining soil or a container in a sunny spot, then thin the seedlings to 10 to 20 cm (4 to 8 in) apart (RHS), or 25 to 30 cm (10 to 12 in) (Penn State). Results are less reliable than sowing indoors.
- Sow indoors 4 to 6 weeks before the last frost.
- Plant out when nights stay above 10 °C (50 °F).
- Sow a small batch every few weeks until midsummer.
How to grow basil from seed
Basil seed wants warmth and moisture to germinate, then bright light.
-
Fill small pots or modules
Use damp, peat-free seed compost.
-
Sow thinly
The RHS scatters seed on the surface; Penn State sows about 6 mm (¼ in) deep. Either works in warm, damp compost.
-
Keep it warm
About 20 to 24 °C (68 to 75 °F): the RHS gives 20 °C (68 °F), Iowa State about 24 °C (75 °F). Use a propagator or a clear plastic bag.
-
Give seedlings bright light
A warm, bright windowsill, out of fierce direct sun. See light.
-
Water sparingly
Seedlings are prone to damping off. Keep the compost damp, never wet.
-
Pot on when they have several leaves
One seedling to a 7.5 cm (3 in) pot, or several 7.5 cm (3 in) apart in a larger pot.
-
Pinch out the tips
To make bushy plants. See pinching and picking.
How to plant out basil
In early summer, for bought plants and your own seedlings.
-
Harden off over about two weeks
Stand the pots outside in a sheltered, lightly shaded spot by day and bring them in at night.
-
Choose a warm, sheltered, sunny spot
In the ground, a container or a greenhouse border. See where it grows best.
-
Plant at the same depth
At the level it was growing in its pot.
-
Space them out
In containers, at least 10 cm (4 in) apart (RHS). In beds, 25 to 30 cm (10 to 12 in) between plants (Penn State, UMD) and 45 cm (18 in) between rows (UMD). Crowded basil flowers sooner and catches disease.
-
Water in, in the morning
Water the soil, not the leaves. See watering.
Rescuing a supermarket pot of basil
A supermarket pot is dozens of seedlings crammed together, grown in about 22 days for a short life. Split them up and they can crop all summer.
-
Tip the plants out
Do it as soon as you get it home: crowded pots soon rot or flower.
-
Tease the roots apart
Gently separate the seedlings, keeping as much root on each as you can.
-
Pot them up individually
Each into its own pot of soil-based compost.
-
Keep them warm, moist and out of direct sun
Moist but not wet, while the roots settle.
-
Plant out when the roots fill the pot
Once roots show through the drainage holes, harden off and plant out, or keep them growing indoors. The RHS advises growing supermarket plants indoors, to limit disease spread.
Care
Keep it warm and evenly moist, and pinch it often so it stays bushy.
Pick off flower stems as soon as you see them to keep the leaves coming.
Care by growth stage
Seedling
Water: sparingly · Light: bright
Warmth and bright light. See growing from seed.
Young plant
Pinch: above the second leaf pair
Pinch it to make it branch. See pinching and picking.
Summer
Water: keep evenly moist · Pick: shoot tips often · Flowers: pinch off
The main harvest. See watering.
Autumn
Move: indoors before cold nights
As nights cool, bring pots indoors or cover plants with cloches. See indoors.
Watering basil
Keep the soil or compost evenly moist: if it dries out, basil wilts quickly, but it also rots if its roots sit wet.
New plants. Water well until they are established, then during dry spells.
In pots and greenhouses, water regularly, as they dry out faster. Never leave a pot standing in water.
How. Water the soil, not the leaves, and in the morning if you can: basil hates wet roots overnight, and damp leaves invite grey mould and downy mildew.
Mulch outdoor plants with straw to hold moisture and keep weeds down. Dry conditions also make basil flower sooner.
Feeding basil
Basil in the ground usually needs no feeding at all.
In containers, it can run short of nutrients over the summer as the compost is used up. Give an organic-based, balanced liquid feed, at the rate on the label, to boost leafy growth.
Avoid potassium-rich feeds such as tomato feed, which encourage flowering, and heavy nitrogen, which dulls the flavour.
Pinching and picking
Pinching makes a bushy, productive plant instead of a tall, thin one. Every picking doubles as pinching.
First pinch. When a seedling has six leaves, pinch it out above the second pair (Penn State).
Keep going. Each time a branch has six to eight leaves, cut it back to its first pair. Always cut just above a pair of leaves, where the new side shoots come from.
How hard. You can be ruthless, as long as you leave at least three pairs of side shoots to regrow (Gardeners’ World).
Flowers. Flowering, usually from mid to late summer, dulls the leaves’ flavour. Pinch off flower stems as soon as you see them. Late in the season, let a few plants bloom: the flowers are rich in nectar for bees, and edible.
Basil in containers
Basil often does better in a container than in the ground: a pot drains freely, warms up faster and is simpler to protect from slugs.
Pot size. At least 20 cm (8 in) wide and deep, in peat-free multi-purpose compost, plants at least 10 cm (4 in) apart.
Growing on. Plants grow fast, so expect to pot them on a few times in a season.
Care. Water regularly and feed occasionally. See watering and feeding.
Growing basil indoors
Basil grows well on a warm, bright windowsill, which is also the most reliable way to start it.
Light. A sunny window; turn the pot so it grows evenly. Expect a slightly less intense flavour than outdoor basil.
Autumn move. When temperatures start to dip, bring a few plants back indoors for fresh leaves into winter.
Air. Space pots so air can move around them.
What to grow with basil
Companion planting claims range from well evidenced to folklore. Each one here is labelled with the evidence behind it.
Tomatoes
Grow together · Wants the same conditions
They enjoy the same warm, sheltered spot and steady moisture, and the tomatoes cast light shade over basil at the hottest time of day.
Problems
Cold, wet roots and crowding cause most basil trouble; downy mildew is the one serious disease.
Common basil problems
These are growing problems, not pests or diseases.
Flowering early
- Dry soil
- Crowding
Dry conditions and overcrowding push basil into flower sooner. Water evenly, thin plants out, and pinch off flower stems.
Lanky seedlings
- Low light
Seedlings in poor light stretch and transplant badly. Give them bright light as soon as they appear.
Blackened or collapsed plants after a cold night
- Cold
- Frost
Basil is readily damaged by cold. Keep it indoors until nights stay above 10 °C (50 °F), and bring it in or cover it in autumn.
Supermarket basil dying
- Crowded roots
The pot holds too many weak seedlings. Split it up; see rescuing a supermarket pot.
More problems with basil
Common pests
Slugs and snails
They eat holes in the leaves, worst in shady, wet or crowded plantings. Growing in pots keeps them off more reliably.
Aphids
Sap-suckers that reduce vigour and distort growth. Wipe or rinse them off; ladybirds and other predators help outdoors.
Whitefly and red spider mite
Mostly under glass. Check the undersides of leaves; treat heavy infestations with a suitable insecticide or a biological control.
Leafhoppers
Cause a coarse, pale mottling on the leaves in spring and summer; usually cosmetic.
More problems with basil
Common diseases
Basil downy mildew
The one serious basil disease, spreading fast in warm, humid weather. Leaves yellow between the veins, often mistaken for hunger, then brown, curl and die, with grey-purple fuzz underneath. There is no cure, and fungicides sold to home gardeners don’t control it. Harvest any healthy leaves at once (they are safe to eat), then bag and bin the plants. Prevent it with resistant varieties, sun, wide spacing and no overhead watering.
Grey mould
Fuzzy grey growth on soft tissue, worst in damp, still air. Water the soil, not the leaves, before midday, and ventilate greenhouses.
Fusarium wilt
A problem where the disease is present in the soil. ‘Elidia’ is resistant.
Harvest & Use
Pick shoot tips all summer, and use the leaves fresh for the best flavour.
Harvesting basil
You can start picking about six weeks after planting, and keep going all summer.
How. Take shoot tips, a few from each plant, as described in pinching and picking. For pesto, you can harvest whole plants.
Best flavour. Just as flower buds form but before they open; flavour fades once seed sets.
Washing. Gardeners’ World washes leaves only just before use, as wet leaves turn slimy; Iowa State washes and pats them dry, then uses or refrigerates them.
End of season. Before the first cold nights, pick heavily or bring plants indoors.
Storing and using basil
Basil is best used fresh. Cooking dulls its flavour, so add it at the end or scatter it over a dish just before serving.
Short term. Stand cut stems in a glass of water in a cool spot for a few days, changing the water daily. Or keep dry leaves in a perforated bag in the fridge.
Freezing and drying. Gardeners’ World finds basil hard to dry or freeze well; Iowa State and Penn State do both. To freeze, bag whole leaves, or chop them into ice-cube trays topped with water or olive oil. To dry, spread leaves on racks in a warm, airy place out of the sun; well-dried leaves stay green and brittle, while brown leaves mean too much heat and lost flavour. Store them straight away in an airtight jar somewhere cool, dark and dry.
Uses. Pesto, tomato dishes, salads and Thai cooking; lemon and cinnamon basils flavour jams, vinegars and sorbets. The flowers are edible too.
Propagation
Root a shoot in a glass of water, or split up a supermarket pot.
Propagating basil
Basil is usually grown from seed, but it roots readily from softwood cuttings in summer.
- Snip off a non-flowering shoot just below a leaf.
- Remove the lower leaves and pinch out the tip.
- Stand it in a jar of water on a warm windowsill. Roots form quickly.
- Pot it up in peat-free multi-purpose compost once it has roots, usually within a few weeks. Cuttings also root directly in compost.
Also: a supermarket pot splits into several plants. See rescuing a supermarket pot.
More to Explore
Quick answers, guides that pair well with basil, and the sources behind this one.
Frequently asked questions
Why is my basil dying?
Common causes are cold, wet roots and a crowded supermarket pot. Yellow leaves with grey fuzz underneath mean downy mildew. See common problems.
How do I stop basil flowering?
Pinch off flower stems as soon as you see them, keep it watered, and don’t crowd it. See pinching and picking.
How often should I water basil?
Often enough to keep the compost evenly moist but never soggy, in the morning, at the base. See watering.
Can I grow basil indoors?
Yes, on a warm, sunny windowsill. The flavour is a little less intense than outdoors.
How do I make supermarket basil last?
Split it into small clumps and pot them up separately. See rescuing a supermarket pot.
When can I put basil outside?
After your last frost, once nights stay warm. See when to sow and plant.
How do I pick basil without killing it?
Take whole shoot tips, never strip the plant bare. See pinching and picking.
Is basil a perennial?
Many basils are tender perennials, but they need so much warmth that they are grown as annuals.
Is basil safe for cats and dogs?
Yes: the ASPCA lists basil as non-toxic to dogs and cats.
Can you freeze basil?
Yes, as whole leaves or chopped in ice cubes with water or oil, though it loses some texture. See storing and using basil.
Related guides
Sources
- How to grow basil (opens in a new tab) Royal Horticultural Society
- Basil (opens in a new tab) ASPCA Animal Poison Control
- Growing basil in the home garden (opens in a new tab) Iowa State University Extension and Outreach
- Growing basil in a home garden (opens in a new tab) University of Maryland Extension
- Downy mildew on basil in the home garden (opens in a new tab) University of Maryland Extension
- Basil, a summer favorite (opens in a new tab) Penn State Extension
- Basil downy mildew (opens in a new tab) University of Wisconsin-Madison Extension
- How to grow basil (opens in a new tab) BBC Gardeners’ World