May, north of the equator

May is when the year finally lets go of the brake. The last frost passes in most places during the month, the soil is warm enough for anything, and the difference between a plant sown now and one sown in March has almost disappeared. It is also the month of the greatest single loss, because one late frost in the first fortnight can take every tender thing in the garden.

In the garden

Plant out everything tender once your own last frost has passed: tomatoes, courgettes, cucumbers, pumpkins, squash, sweetcorn, French and runner beans, dahlias and the summer bedding. Harden it all off first. Keep fleece to hand for the first fortnight, because the forecast is wrong often enough to matter.

Sow directly into warm soil. Beans, beetroot, carrots, chard, lettuce, radish and salad leaves all germinate in days now rather than weeks, which is why May sowings so often catch up with April ones. Sow biennials such as foxglove and honesty for next year, and keep a short row of lettuce going every fortnight.

Plant bougainvillea and other frost tender things in pots that can come back under cover in autumn. Delosperma, echinacea and the later perennials all establish well now. Stake dahlias and tall perennials as you plant them, while the roots are still small and a cane can go in without doing damage.

In the house

Take the houseplants outside, in stages. Full shade for a week, dappled light for another, and only then somewhere brighter, and never straight into midday sun. A summer outdoors gives most foliage plants more growth than the whole of the rest of the year, but the transition has to be gradual.

Water and feed properly. This is peak growing season, and a plant in active growth in good light wants the shortest interval of its year. Watch anything on a south facing windowsill, which can now go from damp to bone dry in two days.

Pot on anything that missed March. There is still time for roots to fill fresh compost before the season turns, though after June it becomes a job for next spring.

What not to do yet

Do not put a tender plant out and then go away for the weekend without checking the forecast. Do not leave houseplants in full sun to acclimatise, which is not what acclimatising means. And do not rush the last frost. A fortnight of patience costs one picking of beans, and a wrong guess costs the whole plant.