Growing

Before you reach for the feed, find the leaf that yellowed first and look at where it sits. Old leaves at the base point to hunger or age. The newest leaves at the tip point to iron. Speckles, spots or yellow edges send you to the underside of the leaf. Each pattern below has a quick check and a first step for today.

The gadget you buy matters far less than two boring things: how much water sits in the reservoir, and whether every pot keeps even contact with it. A £79 timer...

Greenhouse tomatoes catch blight far less often than outdoor ones, until a warm wet August lets it in. How to identify blight in 60 seconds, what to do the moment you find it, and the varieties that keep it out.

Three of the commonest fruit problems in a greenhouse, blossom end rot, splitting and patchy ripening, trace back to watering that comes and goes, according to the RHS. The rest of the season is simple by comparison: sow in late winter, plant out when the house stays warm, pinch out side-shoots and feed once the fruit swells. Here is the year in order, with a table for the problems you are most likely to meet.

By 11am on a warm Saturday a closed 8x6 greenhouse can sit at 35°C. The three moves that bring it back down: the RHS 20% vent rule, shading compared, and a 10-minute heat-day routine.