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Summer annuals

Published on November 21st 2020
A close up of a flower
Summer annuals can transform almost any patch of soil or dull corner into a vibrant, colourful display. By simply sowing seeds of annuals at the start of the season, you can grow a beautiful summer garden without much effort. Whether you start in seedling trays or directly into beds, containers or hanging baskets, you have to give summer annuals a go this season!
A vase of flowers on a table
Most annual plants can be sown directly into the ground from early spring onwards for spring and summer flowering.

Summer annuals planting tips

  • For the most effective display, position plants in groups., and group according to colour and height.
  • When sowing or planting summer annuals it is important to group plants with similar light and water requirements together.
  • Plant the tallest varieties at the back, medium-height in the middle and the lowest at the front.
  • When growing annuals in containers consider planting low-growing or those with a trailing habit like cascade petunias for sunny spots or petunias for shady positions.
  • To brighten up perennial borders, plant annuals in the spaces between the permanent plants.
A close up of a flower

Preparation is key

  • Before sowing, start preparing the beds by removing old plants left from the previous season.
  • Dig over garden beds, add a generous dressing of compost, and scatter a light dressing of bone meal (high in phosphorous to help flower formation).
  • Just before sowing seeds or planting seedlings, rake the soil to obtain a crumbly, easily worked surface.
  • If you’re planting in containers or hanging baskets, use potting soil that drains well and retains moisture.
  • Water seedlings well before planting out.
A pink flower on a plant

Time to plant!

Direct sowing
  • Seeds can either be scattered over the whole area or sown in grooves.
  • When considering the distance between the grooves, keep in mind the size and height of the plants at maturity. Usually, this information can be found on the seed packet.
  • After sowing seeds in grooves or scattering across the bed, lightly cover them with soil by raking along the length of the grooves.
  • Firm down the soil with the flat side of a rake, ensure most seeds are covered and protected from the sun.
Tip | Sow seeds thinly to make thinning easier.
A person standing in a garden
Transplanting seedlings
  • Plant out seedlings on a cool overcast day, or early in the morning or later in the afternoon when the sun is less harsh.
  • When removing seedlings from their trays, do not pull the leaves or stems, rather push out the root ball from the bottom of the seedling tray.
  • Plant seedlings out at the same depth as they were growing in the seedling tray.
  • Gently firm down the soil to remove air pockets and water thoroughly.
  • Check on your plants regularly to ensure the newly planted seedlings do not dry out.
Tip | Rather than sprinkling lightly, water the seedlings deeply to encourage deep root growth.
A box of pizza

Caring for annuals

  • Fertilise seedlings with a good general fertiliser for flowering plants. For garden beds, use a granular fertiliser and for containers or hanging baskets, use a liquid fertiliser.
  • Remember to deadhead flowers to keep your plants neat and tidy and also to encourage flower production.
A close up of a bunch of pink flowers

Summer annuals

Pearl everlasting

Anaphalis spp.


Angelonia spp.

Bells Of Ireland

Moluccella laevis

Brugmansia plant

Angel's Trumpet

Brugmansia spp.

A close up of some purple Campanula medium flowers

Canterbury Bells

Campanula medium

Chinese Aster

Callistephus chinensis


Iberis umbellata


Dianthus spp.


Celosia spp.

A close up of some purple Centaurea cyanus flowers


Centaurea cyanus


Cosmos bipinnatus

A close up of a white Nierembergia flower and some green leaves


Nierembergia spp.

Everlasting Pearl

Anaphalis margaritacea

Floss Flower

Ageratum spp.


Myosotis spp.

Garden Dahlias

Dahlia spp.

Treasure Flower

Gazania spp.

Baby's breath

Gypsophila spp.


Alcea rosea


Delphinium ajacis

Leucanthemum paludosum

Leucanthemum paludosum

Some purple Lobelia flowers


Lobelia spp.


Nigella spp.


Lupinus spp.


Tagetes erecta

Some colourful Calibrachoa flowers

Million Bells

Calibrachoa spp.

A close up of a green Tropaeolum majus plant with a red flower


Tropaeolum majus


Phlox spp.

Petunia flower


Petunia spp.

Portulaca grandiflora flower


Portulaca grandiflora


Antirrhinum spp.

Spider Flower

Cleome houtteana

Satin Flower

Clarkia amoena


Helianthus annuus


Sutera spp.

Sweet Alyssum

Lobularia maritima

Sweet William

Dianthus barbatus


Linaria vulgaris

Tropical Sage

Salvia splendens

Trailing Phlox

Chaenostoma cordatum

A close up of a Verbena flower


Verbena spp.


Vinca spp.


Zinnia spp.

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