Seeds to Sow in September

Seeds to Sow in September

Seeds to Sow in September

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September is the start of autumn sowing season! It's a great time to get ahead of the game for next year by sowing certain seeds early to give them a head start before the frosts come.

From sweet peas to wildflowers, there are lots of flowers you can sow in autumn. Plus you can continue to keep your veg patch active with winter lettuce or winter cabbage.

Don't leave your veg patch empty once you've harvested this month, instead sow Unwins Green Manure to add nutrients back into your soil to prepare it for a bountiful growing year next year.

To see all seeds that can be sown in September, take a look here.

seeds to sow in august

Top Seeds to Sow in September

Sweet Peas

Sowing sweet peas in autumn is good practice as it allows the seedlings to grow and develop over winter, resulting in more robust plants that begin to flower earlier in the season. You can even sow some sweet pea seeds in autumn, then sow more in spring to ensure your flowering display is extended for the entirety of the summer.


Top Tip - Use a deep root propagation tray to allow your seedlings to develop long and healthy roots over the colder months. Learn more about how to grow sweet peas.


For a truly dazzling display, choose a number of complementary sweet pea varieties, or a mix that includes a selection of colours. Try Unwins Sweet Pea 120 Years for large, frilly flowers with beautiful fragrance.  


Winter lettuces are a fantastic crop for providing fresh salad in the colder months. The veg patch is often empty during the winter months, so growing lettuce not only keeps something growing in the soil, but also provides you with a crop in late winter when there isn't much else to harvest!


Try sowing Unwins Cos Lettuce Winter Density. This is a slow to bold, winter hardy variety with a long cropping period and good disease resistance. The dense heads are packed with frilly leaves which you can pick as required.  


This variety is an RHS Award of Garden Merit winner and as well as being perfect for sowing now, and harvesting in winter, it can also be grown as a summer cropper, giving you even more time to sow the seeds and enjoy!


There are many wildflowers that can be sown as autumn starts in order to give them a good amount of time to grow before the first frost. This will give them a head start come spring and ensure you get a summer full of flowers, which not only you will enjoy, but the pollinators will be very grateful for too.


Wildflower plants often set seed naturally at this time of year, so by sowing in September, you are mimicking the natural behaviour of these plants. The warmth from September sun will help your seeds germinate, and you can expect your wildflowers to bloom earlier next season.


The Unwins range includes many different wildflower varieties for you to sow in September. For beautiful, tall spires of white and pink flowers, try sowing Unwins Verbascum Snowy Spires.


Poppies seeds can be sown in autumn for the best chance of flowers the following year. Poppies like a sunny spot with good drainage and a fine seed surface, so rake your soil first and remove any weeds.


For the most natural effect, sprinkle your poppy seeds thinly across the ground to create a drift pattern. Germination shouldn't take too long in September, expect anywhere from 7-30 days depending on the variety. Keep the area watered, but not soaking, to help germination and give your seedlings the best start.


Try sowing Unwins Poppy Lauren's Grape this September for beautiful purple flowers next summer. These richly-coloured, bowl-like blooms are a rich plum colour and will add incredible colour to your garden.

Other seeds to sow now



Seeds to sow


  • Hollyhock
  • Yellow Rattle
  • White Clover
  • Viola
  • Salvia
  • Red Campion
  • Ox-Eye Daisy
  • Nepeta
  • Nemesia
  • Love In a Mist
  • Lathyrus
  • Cornflower



Seeds to sow


  • Spinach
  • Rocket
  • Radish
  • Cress
  • Winter Cabbage
  • Broad Beans



Seeds to sow


  • Chervil
  • Mint
  • Parsley
  • Watercress
  • Basil

Caring for Plants


Continue to water & feed your plants throughout September in order to give them the final nutrient boost they need to flower and fruit for as long as possible. Deadheading is also key this month to extend your flowering season as long as possible. Use a pair of sharp snips and regularly snip off spent flower heads to delay your flowers going to seed.




As long as the weather holds out, you will have plenty to harvest throughout September! Aubergines, tomatoes, beetroot, broccoli, cabbage, carrots, cauliflower, celery, courgette and salads will be at their peak, so it's time to start thinking of recipes and sharing your harvest with friends & family so nothing goes to waste! When harvesting, make sure to make a note of any varieties you've loved growing this year, to ensure you grow them again next year!


Thinking About Next Month


We can continue to autumn sow many flowers and vegetables next month, getting seeds into soil before the frosts come! Sweet peas, wildflowers, poppies and love in a mist are just some of the flowers you can sow, plus herbs such as parsley and mint can be sown in October too.


More Seeds to Sow in September...