Basil
This popular annual herb is an essential ingredient in Italian cooking with strongly flavoured leaves that can be used to perk up tomato dishes or blitzed to make pesto sauce. Seeds are best sown indoors in late winter or early spring for plants that can be grown outdoors in summer, providing leaves that can harvested well into the autumn.
Jobs to do now
- Continue harvesting
- Remove flowers
Month by month
Sow
Seeds are best started off indoors from late February to mid-summer. Fill a 7.5cm (3in) pot with seed compost, firm down and sow a few seeds of basil over the top – most will germinate so only sow a few more seeds than you need. Cover with a thin layer of vermiculite, water gently and pop it into a propagator. If you don’t have one, don’t worry. You can cover the pot with a small, clear freezer bag and secure with an elastic band.
After germination, remove from the propagator (or take the bag off) and keep damp. When the seedlings are large enough to handle and have developed their first true leaves (ignore the rounded seed leaves), give them their own 7.5cm (3in) pot filled with multi-purpose compost.
Grow
Plant basil outside after all danger of frost has passed, choosing a sunny, sheltered spot with well-drained soil or grow plants in containers. You can keep a plant in a pot going all summer long by moving it into a slightly bigger container every time roots show through the drainage holes in the bottom – plants could end up in a 20cm (8in) container.
Basil hates having wet roots overnight, so aim to water plants in the morning if possible.
Keep plants bushy and productive by pinching the tips of branches regularly and remove any flowers that start to develop.
Common problems
Aphids
Look for colonies of greenfly on the soft shoot tips of plants or on leaves. They suck sap and excrete sticky honeydew, encouraging the growth of black sooty moulds.
Remedy
Use your finger and thumb to squash aphid colonies or use biological control in the greenhouse.
Slugs and snails
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These feed on the young seedlings and you'll see the tell tale slime trail on the soil around your crop, as well as on the leaves.
Remedy
There are many ways to control slugs and snails, including beer traps, sawdust or eggshell barriers, copper tape and biocontrols.
Harvesting
Basil leaves can be harvested throughout the summer.
Remove leaves as required or harvest entire plants if lots of leaves are needed to make pesto or sauce.
If only a few leaves are required, remove the tops of plants to encourage bushy growth.
Recommended Varieties
Cinnamon
Bushy plant with aromatic red veined green leaves.
Genovese
Large, bright green sweet leaves that are brilliant with mozzarella and tomatoes.
Napoletano
Huge leaves for perfect pesto.
Purple Ruffles
Showy dark leaves which are heavily fringed.
Siam Queen
Tasty, slightly hairy oval leaves are great for Thai cooking.
Get involved
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.