PlantyBoxPot and soil
A pot at least 20 cm (8 in) wide for one plant, or a long trough with seedlings 15-20 cm apart. Use light, all-purpose potting mix with some perlite and good drainage: basil loves water but hates soggy roots.
Light and position
At least 6 hours of sun a day. In very hot climates a little afternoon shade keeps the leaves large and tender. It hates the cold: growth stops below 10 °C (50 °F) and leaves blacken below 5 °C (41 °F).
Watering
In summer roughly every 2 days, daily in a heatwave, always at the base and ideally in the morning. Keep the soil moist but never soggy. If it rained, skip it: PlantyBox does this automatically from your local forecast.
Feeding
A nitrogen-rich liquid feed for herbs or leafy plants every 2 weeks through the growing season. Too much fertilizer gives big leaves with less aroma.
Harvest
The plant is 15-20 cm tall with at least 3-4 pairs of leaves.
How to harvestPinch the tip just above a pair of leaves so it branches. Remove flowers as soon as they appear.
Common problems
Usually too much water or a pot that doesn't drain. If only old, lower leaves yellow, the plant may be short of nitrogen.
Cold (below 10 °C / 50 °F) or water on the leaves in full sun. Spreading spots with grey fuzz underneath mean downy mildew: remove affected leaves and water only the soil.
It wasn't pinched and is going to flower. Cut just above a pair of leaves and it grows back bushier within two weeks.
FAQ
How often should I water basil in a pot?
About every 2 days in summer, daily in hot weather. Push a finger into the soil: if the top 2 cm (1 in) is dry, water.
Should I remove basil flowers?
Yes. Once it flowers the plant stops making leaves and turns bitter. Pinch off flower spikes as soon as they appear.
Can I keep basil indoors in winter?
Yes, on a very bright windowsill away from radiators, but it grows slowly. It's often easier to sow again in spring.
