September, south of the equator

September is the largest month in the southern gardening year. Everything can be sown, everything can be planted, and the whole summer is ahead. The one restraint worth exercising is not doing it all in a single weekend, because a garden sown on one Saturday arrives on one Saturday four months later.

In the garden

Sow the vegetables directly: beans, sweet corn, Swiss chard, baby marrow, pumpkin, gem squash, carrots, turnips, radish, onions, spring onions, beetroot, cabbage, cucumber and lettuce. Plant out tomatoes, peppers, eggplant and potatoes. Sow the herbs, which is basil, parsley, rocket, fennel, dill and salad burnet.

Plant the summer bulbs. Dahlias, arums, irises and liliums all go in now. Plant the summer annuals and bedding: cosmos, marigold, zinnia, petunia, nasturtium, alyssum, salvia, dianthus, gazania, lobelia, portulaca, vinca and sunflowers. Plant clivia, agapanthus, delosperma, pelargonium and lavender, and put in the trailing daisies and other indigenous ground cover before the heat.

Feed everything and mulch afterwards. Set up the watering before you need it. Sow in short successions rather than in one long row, especially lettuce, beans and radish, so that the harvest arrives over weeks instead of days.

Succession, and why it matters more here

A southern spring is short and the heat that follows it is long, which makes succession sowing more valuable than it is in a cooler climate. A single sowing of lettuce or beans in early September gives you a fortnight of glut and then nothing until autumn. The same seed sown in three lots a fortnight apart gives six weeks of picking, and the later sowings are the ones that carry through the first hot weeks. The same applies to radish, rocket, carrots and beetroot.

Sow half a packet and keep the rest. Nothing in the seed tin goes off between September and October.

In the house

The plants are properly awake. Shorten the watering interval, feed at full strength once growth is clearly under way, and expect fast growth in anything with decent light.

This is the best month of the year to repot. Roots out of the drainage holes, water running straight through, or a pot that dries within a day all mean it is time. Go up one pot size only, use fresh compost and water once thoroughly.

Take cuttings of almost anything. Pothos, tradescantia, philodendron, pelargonium and string of pearls all root within weeks in spring warmth, and a cutting taken now is a full plant by autumn.

What not to do yet

Do not put a plant that wintered indoors straight into full sun, even for an hour. Do not sow the whole packet. And in the coldest inland gardens, keep something over the tender seedlings for the first fortnight, because a late frost in early September is not unheard of.