Growing Basil in Scotland: The Complete Guide

Ocimum basilicum

The honest guide to growing basil in Scotland: it is a windowsill or greenhouse crop, not a bed crop. We have done the research so you don't have to.

Basil is the one herb this guide will tell you not to plant in the garden. It is not hardy in the UK. It needs about 20C to germinate. It needs nights consistently above 10C to survive outdoors. Much of Scotland does not reliably clear that bar in July. The good news is that basil does not need a garden at all. A pot on a bright kitchen windowsill, sown in March or April, gives you fresh leaves from May through September. A greenhouse or polytunnel gives you a bigger plant and a longer season. Outdoors is a gamble you can take in a warm summer, but the smart money is on the windowsill.

Why basil needs cover in Scotland

Basil does particularly well in a greenhouse in cooler locations. Scotland is a cooler location. The plant needs warmth to germinate, warmth to grow, and warmth to produce the aromatic oils that give the leaves their flavour. A Scottish summer that never quite gets warm enough gives you a basil plant that survives but produces small, flavourless leaves. The same plant under glass, in the trapped warmth of a greenhouse or polytunnel, produces the lush aromatic leaves that make basil worth growing. A windowsill above a radiator is warmer than a Scottish June.

Varieties

Sweet Genovese is the standard cooking basil, and it carries no AGM. Salvo and Aroma 2 do hold the RHS Award of Garden Merit, a UK-wide award, not a Scottish one. Under glass, growing conditions matter more than variety: a warm windowsill will make any of them perform.

Also worth considering

Sowing and planting

Sow indoors from March to July. Fill small pots with peat-free seed compost. Sow a few seeds per pot, 0.5cm deep, and keep at about 20C on a warm windowsill or in a propagator. Germination takes one to two weeks. Thin to the strongest seedling per pot. Keep the compost moist.

If you want to try basil outdoors, wait until early summer when nights are reliably warm. Plant in a sheltered south-facing spot in well-drained soil. Do not plant out until at least two weeks after your last frost date, and keep fleece handy. Expect a smaller plant and a shorter season.

Care through the season

Water regularly. Basil in a pot on a sunny windowsill dries out fast and may need watering every day in summer. Keep the compost evenly moist but not waterlogged. Water in the morning and try not to wet the leaves.

Pinching out: this is the single action that turns a single stalk into a bushy productive plant. Every week, pinch out the growing tip above a pair of leaves. The plant will produce two new shoots below the cut. Keep doing this and you will have a dense, leafy plant rather than one tall spindly stem.

Flower removal: remove any flower buds as soon as they appear. Once basil flowers, the leaves lose flavour and the plant puts its energy into seed. Pinch out the buds and keep harvesting.

Harvesting: pick leaves regularly from the top of the plant, taking the larger outer leaves first. Harvest in the morning when the oils are strongest. The more you pick, the more the plant produces. A well-maintained plant will crop from May until September or until the light levels drop in autumn.

Common problems

• Yellowing leaves usually means the plant is too cold, too wet, or short of light. Move it to a warmer, brighter spot and let the compost dry slightly between waterings.
• Grey mould appears as fuzzy grey patches on the leaves in damp stagnant conditions. Improve airflow. Remove affected leaves. Water only in the morning.
• Aphids cluster on the new growth. Wipe them off with a damp cloth, or spray with soapy water. Check the undersides of leaves regularly.
• Leggy plants mean you are not pinching out the growing tips. Cut the plant back to a pair of healthy leaves and it will bush out.

Common questions

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