Growing annual flowers is fun, as well as very rewarding; sowing seeds and watching them grow into beautiful flowers.  Children are also fascinated by watching seeds germinate and develop through different stages.

  • Annual flowers can extend the period of colour in your garden through the summer and into late autumn.
  • Some annuals are particularly beneficial for pollinators and can deter pests in gardens and vegetable plots.
  • Annual flowers are great to fill in gaps in newly planted gardens and summer containers.
  • Some annual make great cut flowers you can bring into your home or give as gifts.
Seed trays in an unheated greenhouse

Seed trays in an unheated greenhouse

Equipment needed for Sowing Seeds

You can sow seeds directly in the ground but unless you have a specific bed for this your seedlings may struggle to compete with established plants and weeds.  So to start seeds in pots/trays you need:

  • Warm and light under cover area (window ledge, conservatory, greenhouse, polytunnel, pop-up greenhouse)
  • Shallow Trays and/or small pots with drainage holes
  • Clear plastic covers or plastic bags
  • Seeds, seed compost, labels and watering can

How to Sow Seeds

Fill pots/trays to the top with seed compost, only firming in when full to leave a 1cm gap between the compost surface and top of the container.  Water the container well; until water drips out of the bottom.  Then sow seeds; scatter small ones on the surface and cover with a little more compost.  Large seeds should be pushed individually into the compost about 2cm apart, check the correct depth on the seed packet, and then cover them over with compost.  Remember to label the container with the seed name and date of sowing.

Place the containers in a light, sheltered place.  Some seeds may need heat, others will germinate in an unheated greenhouse, cold frame or pop-up plastic greenhouse.  Check the seed packet for details.  In warm environment a clear plastic cover or bag over the container will help stop your seedlings drying out too quickly.


Aftercare and “Pricking Out” for Seedlings

Seedlings are very vulnerable to diseases and a poor growing environment.  So make sure your pots and trays are kept clean and hygienic.

They should have good light, but beware long periods of direct, strong sunlight and too much heat.  Turn your pots/trays if germinating plants on a windowsill to prevent seedling growing towards the light and bending (see the photo below on the left).

Seedling growth - the left shows seedlings that have too much heat

Seedling growth – the left shows seedlings that have too much heat

Keep compost moist with frequent, light watering but be careful not to waterlog the seedlings if the growing space is not heated.  If you see green algae on the compost surface stop watering until the compost dries out a little and try watering from the bottom of the pots/trays by standing them in a watertight tray.  Capillary matting under your pots/trays is great; it will absorb water and reserve it for the compost to draw on over a longer period of time.

Seeds of plants will germinate at different rates from a few days to three weeks – give them time to grow and be patient!  Larger seeds often grow their roots before shoots, so you may not see shoots quickly.

Cosmos seedling with 2 sets of leaves, ready for pricking out

Cosmos seedling with 2 sets of leaves, ready for pricking out

“Prick Out” seedlings when they have at least 2 pairs of leaves (see photo) and put them into their own small (6cm diameter) pots with multipurpose compost.  Lever their roots gently out of their original container and hold by the stem when moving.  Firm in the compost around the seedling to keep it upright and water well.  When the plant roots fill this pot it should be ready to plant out into the garden or containers.  Remember ‘tender’ plants should not be put outside until the frosts have finished in late May/early June.

Reliable varieties of Easy-to-Grow Annual Flowers

Cornflower, Californian Poppy, French Marigold

For flowers through to the autumn (also ideal for vegetable plots and they attract bees and protect from pests)

  • Nasturtium – Tropaeolum
  • Pot/French Marigold – Calendula officinalis
  • African Marigold – Tagetes
  • Sunflowers – Helianthus annuus
  • Borage – Borago officinalis


For cut flowers

  • Ammi majus
  • Corncockle – Agrostemma githago
  • Cornflower – Centaurea cyanus
  • Purple tansy – Phacelia tanacetifolia
  • Annual Phlox, Cosmos
  • Annual Dahlia, Nigella damascena
  • California poppy – Eschscholzia californica

UK Seed Suppliers

Hands-on Workshops

I run practical, hands-on workshops which will take you through seed sowing techniques for different types of plants (flowering and edible).  At the end of the workshop you can take home your seed trays and grow them on at home.  Click here for details of the next workshop.