Vegetable Seeds to Sow in September: Extending Your Harvest

September 12 2025, by Ellen Rignell, 5 min reading time

Wondering what seeds to sow in September?

In the UK, we're lucky to have mild autumn weather which allows plants to get established before the onset of winter. There are loads of seeds you can sow now to extend your harvest and create a productive winter vegetable garden.

Key Benefits of Sowing in September:

Daylight hours in September are similar to those in March and April so there is plenty of light for seedlings to put on healthy green growth.
Soil temperatures are still warm, allowing plants to quickly establish strong root systems which will keep them cropping through the winter and into early spring.

Key Considerations for September Sowing:

Soil Preparation: Ensure your soil is cleared of weeds before planting. It's best to mulch your soil with compost or leafmould prior to planting - this will protect your soil from winter rain. Once plants are established, you can also mulch with straw to provide the soil with extra protection.
Location: Choose a sunny spot. As days shorten, every bit of light counts!
Frost Protection: While September is usually mild and frost-free, it pays to be prepared with horticultural fleece and cloches, just incase.

Vegetables to Sow in September

Leafy Greens

There are tonnes of winter greens you can sow now to keep your salad bowls full through winter and early spring. They are perfect for sowing direct into the soil or for growing in containers. Growing a mix of varieties is often the best strategy for extended harvests. The choice can often be overwhelming so Ellen has curated a 'Cool Greens' Seed Collection, with 6 different varieties, to help your grow a well-balanced mix of winter salad leaves.

Spinach: An excellent winter green that sweetens in cool weather. Grow in containers if slugs are a problem in your garden. We love 'Matador' for its winter hardiness.
Winter Lettuce: Look for hardy varieties like 'Wintercrop' and 'Grenoble Red'
Salad Rocket: This fast-growing, peppery leaf can be harvested within weeks and will keep cropping until early spring. 'Astro' is a brilliant variety for harvesting over a long period while 'Victoria' is extremely fast growing from direct sowing.
Salad Mustards: One of the most reliable winter salad greens to sow in September. They come in a gorgeous diversity of colours and shapes. We love 'Pizzo' for its frilly leaves; 'Rouge Metis' for its red, lacy leaf shape; and 'Vivid Choi' for its bright purple colouring and mild flavour.
Lamb's Lettuce (Corn Salad): Very hardy and can withstand cold temperatures, making it a reliable winter crop.

For an more in depth guide to growing Winter Salads and Greens, download our FREE Winter Salad Growing Guide.

Brassicas

Brassicas are very hardy vegetables, making them perfectly adapted to September sowing. Some varieties will crop over the winter while others will crop in spring, during the UK's hungry gap.

Spring Cabbage: A very useful variety for extending harvests into the UK's hungry gap. Varieties such as 'April' will overwinter as a small plant and bulk up into large Hispi-type heads in the spring.
Kale: Hardy varieties like 'Red Russian' or 'Cavolo Nero' can be sown now for a harvest that will last through the winter.

Root Vegetables

Some root crops can be sown now for a late autumn and early winter harvest.

Winter Radishes: Varieties such as 'Rosa' and 'Spanish Black' are quick to mature.

Onions

You still have time to sow bunching onions for winter harvests.

Spring Onions: Hardy varieties such as 'Ischikrona' and 'White Lisbon Winter Hardy' grow brilliantly over winter.

Broad Beans

Broad beans are a UK staple which are usually sown later in autumn (October-November). It's possible to sow in September too, particularly if you harvest the new shoots to eat as greens.

Broad beans: Choose winter hardy varieties such as 'Claudia Aquadulce'

Top Tips for Success

Stay in tune with the weather: The UK is famous for its unreliable weather! Keep an eye on the forecast and adjust sowing as necessary. In a very warm September, consider sowing a little later to ensure plants don't flower prematurely.
Protect from Pests: Slugs and snails can be a problem, especially in wet weather. Plant out seedlings when they are larger and can withstand a few nibbles!
Watering: Outdoor grown plants are unlikely to need watering much because there's usually plenty of rain in a UK autumn! For plants grown in greenhouse or polytunnel, ensure the soil is rehydrated before planting by watering thoroughly. Water plants in too. As weather cools, you're unlikely to need to water much overwinter unless you are on a very sandy soil.

Sowing in September is a great way to extend your gardening season and enjoy fresh, homegrown vegetables into the colder months. Browse our autumn-sown seeds and make the most of the UK's autumn weather!