September marks the start of autumn in the gardening calendar, but most kitchen gardeners will still be enjoying their summer crops. There are a few things that you can do around this time to prolong some of these harvests, and you can also start off new crops to enjoy in the next few weeks, or in the early spring.
Many tender plants will keep on going until the first frost takes them down. This includes:
- vine-type (cordon) tomatoes
- sweet peppers
- some squashes
Cordon tomatoes can be kept going with a good regular dose of high-potassium (potash or K) liquid feed, and the regular removal of side shoots. Look out for extra shoots at the bases of the plants, and also remove any fading or yellowing leaves from the plants as this can encourage disease.
If the tomatoes aren’t ripening, remove any leaves that are overshadowing them. In addition, keep an eye out for signs of blight, and act immediately if you see it – remove any remaining non-affected tomatoes and see if you can ripen them indoors on a bright windowsill. If there’s a frost warning on the weather forecast, that’s your last chance to bring any tomatoes in.
The same thing goes for most pumpkins and winter squash – the first frost is likely to kill the plants and ruin the fruit, so bring them indoors before then and ‘harden’ or ‘cure’ them for 7 to 10 days before storing. You can also improve ripening by removing a few leaves that are casting shade. Removing any small fruitlets that are unlikely to ripen by the end of this month will encourage the plant to put its energy into ripening the larger fruits as well.
Peppers and chillies don’t like being colder than 10 degrees C, so once the weather changes, bring them indoors. They may well flower again if they’re happy, especially if you pep them up with a little half-strength tomato food every few days, and if you’re lucky you could still be getting sweet peppers or chillies into December. This year we finished our last ones in the first week of January.
Brassicas that you’re going to overwinter will benefit from a little mulching, but don’t add too much nitrogen-heavy feed as this can encourage soft growth and reduce hardiness. Larger plants, like sprouting broccoli and Brussels sprouts, do best if you tie them to stakes and earth up firmly around them.
Keep picking any last beans or peas to keep them producing for as long as possible, and when they’re finished, cut them off at ground level and leave the roots in the soil to improve it.
It’s also the last chance to catch up with any summer pruning, and to sort out many woody, perennial or biennial herbs, and so on. For a comprehensive garden jobs to-do list, have a look at the ‘Things to do in September’ article.
Just in case, be ready
If possible, prepare in advance for frost. Depending on where you live, this might not happen until November, but it’s good to have some garden fleece on standby from now onwards. You can also use cloches, move plants indoors or into greenhouses, or improvise with bubble wrap, plastic sheeting, or even newspaper or straw.
As some plants finish, you might end up with bare patches of soil. If you aren’t going to be planting into these spots in the next few days or weeks, cover them with a mulch sheet to keep down any weeds, or sow some ‘green manure’ plants to improve the soil.
It’s also the last chance to get a few things going, including quick crops such as spinach, rocket, oriental greens and baby leaves. Overwintering crops sown now can be grown on under cover and will give you an extended cropping season over the cold months or early growth in the Spring. This includes spring onions, winter lettuces, endive and other hardy salads, leaf beet and chard.
For the full list of seeds to sow now, please see the separate ‘what to sow in September’ article.