Basil Seeds in Ireland

Honestly, not well. In a sheltered sunny courtyard on the south or east coast you may get a reasonable crop in a good July and August, but for most of the country an outdoor basil plant produces a few small leaves and then blackens with the first cold wet spell. The problem is night temperature and humidity rather than daylight. If you want basil in Ireland, grow it in a pot on a sunny windowsill, in a porch, in a greenhouse or in a polytunnel. Treating it as a houseplant that occasionally goes outside on hot days is a far more productive approach than treating it as a garden herb.

In an Irish house, nearly always one of three things: too much water, not enough warmth, or not enough light. Basil wants the compost to dry slightly between waterings, so a plant sitting permanently damp will rot at the base even though it looks like it needs more water. Cold nights on a windowsill behind closed curtains, where the temperature can drop close to the outside air, do the rest. And a north facing window simply does not have the light to keep it going. Move it to the sunniest south facing sill in the house, water in the morning only when the surface is dry, and keep it out of draughts.

Mid-March to early June, indoors, with a minimum of 18C to germinate. There is no point sowing in February here because light levels will produce stretched seedlings that never recover. A late April sowing catches up with a March one very quickly, so if in doubt sow later rather than earlier. A final sowing in early June gives young plants for a windowsill into October. Basil is never sown directly outdoors in Ireland.

Do not try to keep the pot as it is. That pot contains dozens of seedlings forced under glass and crammed together, competing for the same small root ball, which is why it collapses within a fortnight at home. Tip it out, tease the root ball into three or four clumps, and pot each clump into its own 10cm pot of fresh multipurpose compost. Water them in, keep them somewhere bright and warm, and let them dry slightly between waterings. Split like this they will grow on for months instead of weeks.

Yes, and it makes a bigger difference than almost any other thing you do with the plant. Once basil sets flower it redirects its energy into seed, leaf production slows, and the flavour turns noticeably harsher. Pinch out each flower spike as soon as it appears, taking the pair of leaves below it. Better still, harvest by cutting whole stems back to just above a leaf pair, which forces two new shoots from that point and keeps the plant bushy and vegetative for far longer.

You can keep a plant alive but you should not expect much from it. From November to February Irish daylight is too weak and too short for real growth, so the plant sits and slowly declines, and it becomes very prone to rot because it is using so little water. If you want winter basil, a grow light makes it work properly. Otherwise the more practical approach is a last sowing in early June, picking through to October, and starting fresh in March.

Greek bush basil, the small leaved compact type. Its leaves are tiny but it is noticeably more tolerant of the cool and the damp than large leaved Genovese types, and it stays small enough for a windowsill without going leggy. Sweet Genovese is what you want for pesto, but if you have failed with basil before, start with the Greek type to get a feel for the watering.