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What to sow and grow in September

Kniphofia uvariafrom Thompson & Morgan

Sow red hot pokers (Kniphofia) for stunning displays next summer
Image: Kniphofia uvaria from Thompson & Morgan

September might be peak harvest time, but there’s still plenty to sow and grow this month.

Here's a handy list of what to sow in September, including all the flowers, fruits and vegetables to keep your garden ticking along:

Flowers to sow and grow

Verbascum x hybrida 'Snow Maiden' from Thompson & Morgan

Start verbascum off in a cold frame in September
Image: Verbascum x hybrida 'Snow Maiden' from Thompson & Morgan

In the greenhouse/indoors

  • Surface-sow euphorbia seeds now in trays indoors.
  • Sow dierama seed now on the surface of moist compost. Keep in a cool greenhouse over winter.

In the cold frame / under cloches

Direct sow outdoors

  • Sow Ammi majus ‘Graceland’ (Bishop's Weed) directly in the ground now where you'd like it to flower. Autumn sowing will produce bigger, more robust plants to grow.
  • Sow hardy geraniums outdoors and leave them to over-winter.
  • Direct sow hardy annuals, such as cornflowers, poached egg plant, annual poppies and larkspur 'T&M Improved', for bigger plants next year.
  • Sprinkle California poppies into your borders for stunning colour late next spring.
  • Direct sow Love-in-a-Mist (nigella) — it will over-winter quite happily and will self-seed prolifically!
  • Sow delphinium seed this month for flowers next summer.

Plant outdoors

Sedum 'Sunsparkler Dream Dazzler' from Thompson & Morgan

Plant sedum 'Sunsparkler Dream Dazzler' in September for late summer colour
Image: Sedum 'Sunsparkler Dream Dazzler' from Thompson & Morgan

  • Fill gaps in your borders with autumn-flowering plants, such as sedum and Chrysanthemum carinatum 'Polar Star', to extend the colour to the end of the season.
  • Plant hyacinth and amaryllis bulbs for forcing, to ensure a crowd of colourful blooms at Christmas. Keep them in a dark, cool place like a shed or garage and bring them indoors when the shoots are 5cm tall. Perfect for a homemade Christmas present!
  • Plant spring-flowering bulbs, such as daffodils, crocus and hyacinths.
  • Plant out any biennial plants sown earlier in the year. This includes foxgloves, wallflowers and pansy plants.
  • Plant new perennials, trees and shrubs. Now is a good time as the soil is still warm and increasing rainfall should be on its way.

Herbs & vegetables to sow and grow

Radish 'French Breakfast 3' from Thompson & Morgan

September's your last chance to sow summer radishes
Image: Radish 'French Breakfast 3' from Thompson & Morgan

In the cold frame/ greenhouse/ under cloches

  • Direct sow spinach now and offer cloche protection as the weather cools. This will ensure harvests throughout autumn and winter.
  • Sow spring cabbages, such as 'April' and 'Durham Early' into modules in the greenhouse.
  • Sow pak choi ‘Green’ under cloches now for an autumn supply of baby salad leaves.

Direct sow outdoors

  • Sow corn salad (lamb's lettuce) now — it’s a fully hardy crop which can be sown outdoors now for cropping throughout the autumn and winter.
  • Sow green manure on empty beds now to help improve your soil structure and prevent weeds establishing over winter.
  • Sow 'Hi Keeper' onions into a well-prepared seedbed — these are the best variety of onion for autumn sowing. Only thin your onion seedlings in the spring.
  • Direct sow salad leaves now for quick crops.
  • Try sowing the very hardy 'Perpetual' spinach outdoors this month for winter harvests later in the year.
  • Sow winter-hardy spring onions, such as 'White Lisbon' and 'Performer' for crops next spring.
  • Make your last direct sowing of summer radish ‘Rainbow Mixed’ this month for autumn cropping.
  • Sow turnip seeds into well-prepared beds for small roots.
  • Sow winter lettuce, such as 'Arctic King', directly into the ground now.

Plant outdoors

Onion 'Shakespeare' (Autumn Planting) from Thompson & Morgan

September is the time to get onion sets in the ground
Image: Onion 'Shakespeare' (Autumn Planting) from Thompson & Morgan

  • Start planting garlic sets at the end of the month for cropping next year.
  • Plant autumn onion sets this month.
  • Plant out any spring cabbages, like ‘Advantage’, sown during the summer.

Keep one step ahead — what to order this month

Rhubarb 'Champagne' (Spring/Autumn Planting) from Thompson & Morgan

Stock up on rhubarb crowns for planting in September
Image: Rhubarb 'Champagne' (Spring/Autumn Planting from Thompson & Morgan

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