September marks a gentle shift in the garden. The intense heat of summer begins to fade, replaced by the golden light and cooler air of early autumn. For vegetable gardeners, this isn’t an end but a transition, a busy and rewarding month filled with harvesting the last of the summer crops and planting for the cooler months ahead. It’s a time of abundance and preparation, offering a unique opportunity to extend your growing season well into winter.
This guide will walk you through the essential tasks for your vegetable garden this September. Discover which crops are ready to be harvested, what seeds you can still sow for a winter bounty and the key maintenance jobs that will set your garden up for success next spring. Let’s get our hands dirty and make the most of this beautiful gardening month.
Key Jobs for September
September is a month of transition, blending the final summer harvests with preparations for autumn and winter. Keeping on top of a few key tasks will ensure your plot stays productive and healthy.
Tidying and Clearing
As summer crops like courgettes, beans and peas finish producing, it’s time to clear them away. Removing old, spent plants is crucial for a few reasons. It prevents pests and diseases from overwintering in the decaying foliage and frees up valuable space for autumn and winter crops.
When you remove the plants, add any healthy material to your compost heap. Avoid composting anything that shows signs of disease, like mildew or blight, as the spores can survive and infect next year’s crops. For legumes like peas and beans, it’s a good practice to cut the stems at the base and leave the roots in the ground. These roots contain nitrogen-fixing nodules that will enrich the soil as they break down, providing a natural fertiliser for the next plants you grow in that spot.
Preparing Beds for Winter
Once a bed is clear, don’t leave it empty. Bare soil is vulnerable to erosion from winter rain and can lose valuable nutrients. You have a couple of excellent options for protecting and improving your soil over the colder months.
One of the best things you can do is sow a green manure. These are fast-growing plants like phacelia, winter tares, or grazing rye that you grow specifically to improve the soil. They act as a living mulch, suppressing weeds and protecting the soil structure. When you dig them back into the ground in spring, they add organic matter and nutrients, boosting your soil’s health for the coming season.
Alternatively, you can cover the empty beds with a thick layer of well-rotted manure, garden compost, or even a layer of cardboard topped with leaves. This mulch will protect the soil, prevent weed growth, and allow the worms and other soil life to slowly incorporate the organic matter, leaving you with beautifully fertile soil come spring.
Pest and Disease Control
The cooler, damper conditions of early autumn can encourage slugs and snails. Be vigilant around your new seedlings and leafy greens. You can use wildlife-friendly slug pellets, wool pellets, or create beer traps to protect your plants.
Also, keep an eye out for fungal diseases like downy mildew on your brassicas and powdery mildew on any remaining courgette or squash plants. Good air circulation is key, so ensure your plants aren’t overcrowded. Remove any affected leaves promptly to prevent the disease from spreading.
What to Sow in September
While it might feel like the growing season is winding down, September is the perfect time to sow a variety of hardy vegetables that will see you through the autumn and winter.
Winter Salads
Don’t say goodbye to fresh salads just yet. Many varieties thrive in cooler weather.
- Lettuce: Sow hardy winter varieties like ‘Arctic King’ or ‘Winter Density’ directly into the ground or in pots. A cloche or cold frame will offer extra protection and extend your harvest.
- Spinach: September is an ideal time to sow spinach for an autumn and winter crop. It grows well in cooler temperatures and can be harvested as individual leaves.
- Rocket: This peppery leaf is incredibly fast-growing and hardy. Sow a row now, and you could be harvesting it in just a few weeks.
Hardy Greens and Brassicas
These vegetables are staples of the winter garden and should be planted now for a continuous supply.
- Spring Cabbage: Plant out young spring cabbage plants that you sowed earlier in the summer. Choose a sunny, sheltered spot and firm the soil around them well to prevent wind rock.
- Kale: If you haven’t already, you can still sow kale for a late crop of delicious and nutritious leaves.
- Swiss Chard: A beautiful and productive crop, Swiss chard can be sown in September for harvesting through autumn and into winter in milder areas.
Onions and Garlic
Early autumn is the traditional time to get your onion sets and garlic cloves in the ground.
- Winter Onions: Plant onion sets like ‘Radar’ or ‘Electric’ for an early crop next summer. Plant them in well-drained soil in a sunny spot, with just the tips showing above the surface.
- Garlic: Choose a hardneck variety for the best results when planting in autumn. Break the bulb into individual cloves and plant them about 15cm apart and 5cm deep, with the pointy end facing up.
What to Harvest in September
September is a month of great abundance, where you can enjoy the fruits of your summer labour. Many crops will be at their peak, offering a delicious reward for your hard work.
Summer Favourites
The last of the summer crops are often the sweetest, having ripened in the long sunny days.
- Tomatoes: Continue to harvest tomatoes as they ripen. As the month progresses and temperatures drop, you can pick any remaining green tomatoes and ripen them indoors on a sunny windowsill.
- Courgettes and Squash: Keep picking courgettes regularly to encourage the plant to produce more. Winter squashes, like butternut and pumpkins, should be ready now. You’ll know they’re ripe when the skin has hardened, and the stem is dry.
- French and Runner Beans: Harvest beans regularly to ensure a continuous supply. If you leave the pods on the plant for too long, it will stop producing new ones.
Root Vegetables
Many root vegetables planted in spring and early summer will be ready for lifting.
- Maincrop Potatoes: Wait for the foliage to turn yellow and die back before lifting your maincrop potatoes. Choose a dry day and use a garden fork to carefully dig them up. Let them dry on the soil surface for a few hours before storing them in a cool, dark, and frost-free place.
- Carrots and Beetroot: You can continue to harvest carrots and beetroot as you need them. They can be left in the ground, but be mindful of slugs.
- Onions and Garlic: If you haven’t already, harvest your maincrop onions and garlic once the leaves have yellowed and flopped over. Dry them thoroughly before storing.
Autumn Fruits
Don’t forget the fruit!
- Apples and Pears: Early and mid-season varieties will be ready for picking. Gently cup the fruit in your hand and give it a slight twist; if it comes away easily, it’s ripe.
- Autumn Raspberries: These will continue to produce delicious fruit until the first frosts. Pick them regularly to enjoy at their best.
Looking Forward
September in the vegetable garden is a month of balance—a time for enjoying the last of the summer bounty while preparing for the seasons ahead. By clearing old crops, preparing your soil, and sowing hardy varieties, you can ensure your plot remains a source of fresh, homegrown food for months to come.
Take a moment to enjoy the crisp air and the satisfaction of a full harvest basket. Your garden has worked hard all summer, and now is the time to reap the rewards and gently guide it into its winter rest.
Further Reading: Plant Autumn Bulbs Now for a Beautiful Spring Garden, The Autumn Vegetable Garden, All About Seed Saving, All About Squashes, All About Marrows