How to grow annuals from seed
Growing annual flowers from seed is quick, easy and fun, either indoors or outside. The resulting plants are ideal for adding summer colour to borders and containers, and many will attract pollinators to your garden.
- Do it in spring or autumn
- Sow hardy annuals outdoors
- Sow half-hardy annuals indoors
What to sow
Annuals can be hardy or half-hardy:
- hardy annuals are able to survive frost, so can be sown outdoors in autumn or from early spring onwards. Autumn sowings may need protection from hard frosts, but will start flowering much earlier than spring sowings. Examples include cornflowers and pot marigolds – see more choices here
- half-hardy annuals tolerate cool temperatures, but need protection from frost. Sow indoors or in a frost-free greenhouse from early spring, or sow fast-growing types outdoors from late spring, after the last frost. Examples include cosmos and nasturtiums – see more choices here
There is a vast range of annuals to choose from, in every imaginable colour and all shapes and sizes, from lowly forget-me-nots to the tallest of sunflowers. Seeds are widely available in garden centres and from online suppliers – they are relatively cheap, and one packet will usually provide you with a wealth of plants.
See our plant lists for more inspiration:
- Hardy annuals – colour choices
- Half-hardy annuals – colour choices
- Pollinator-friendly annuals
- Meadow annuals
- Spectacular annuals
- Bedding annuals?
How to sow hardy annuals
This method involves sowing directly into the soil, either by broadcasting (scattering seed over the soil surface) or drilling (sowing more precisely in rows). No matter which method you choose, prepare your soil bed in the following way for the best results:
- Make sure the area to be sown is weed-free.
- Dig over the soil to a spade’s depth, rake it over and firm.
- Plan the area to be sown by sprinkling grit or sand on the soil or score the ground with a cane to mark out sowing areas. Decide what should go where according to height, habit and flower colour.
- It is important not to sow into a soil that is too rich, since this may encourage leafy growth at the expense of flowers, so avoid using fertiliser.
- Either broadcast or drill the seed as follows:
Scatter seed thinly over the plots and cover lightly with soil or compost. Aim for a gap of about 0.5cm (¼in) between seeds. Water well with a watering can fitted with a fine rose.
Dividing the bed into irregular patches and sowing into drills (shallow grooves) running in offset directions gives a more natural appearance as plants mature. Space drills 15–45cm (6-18in) apart (depending on the eventual size of the plants). Sow seeds 0.5cm (¼in) apart in each drill, and rake soil over the drills to cover them. Water well with a watering can fitted with a fine rose. As a precaution, beds can be covered with horticultural fleece during cold snaps.
Annuals can also be sown under cover at 18°C (64°F), reducing to 15°C (59°F) after germination. Grow them on into small plants, harden them off for overwintering in a cold frame or unheated glasshouse, and plant them out the following spring.
Suitable annuals to try
Hardy annuals requiring no protection
These hardy annuals may require protection in northern parts of the UK, or even in southern parts if winter is harsh. Keep an eye on the weather, and if hard frosts are forecast, protect sowings with cloches or horticultural fleece.
Ammi majus (bishop's weed): Creamy white lace-like flowers in summer and ferny foliage. Height 30-90cm (1-3ft) and spacing 30-40cm (1ft-16in).
Briza maxima (quaking grass): With creamy-white shimmering spikelets, ideal for dried arrangements. Height 60cm (2ft) and spacing 30cm (1ft).
Calendula officinalis (pot marigold): Slightly aromatic leaves and single or double daisy-like flowers in shades of orange or yellow flowers from summer to autumn. Height 45-60cm (18in-2ft) and spacing 30-37cm (1ft-15in). Centaurea cyanus (cornflower): Dark blue daisy-like flowers from late spring to mid-summer. Height 30-90cm (1-3ft) and spacing 23-45cm (9-18in).
Consolida (larkspur): Delphinium-like spikes of flowers in shades of pink, blue or white. Height 45cm-1.2m (18in-4ft) and spacing 30-45cm (1ft-18in).
Linum grandiflorum (flax): Saucer-shaped rose-pink flowers with dark eyes in summer. Height 30-45cm (1ft-18in) and spacing 10-15cm (4-6in).
Hordeum jubatum (squirrel tail grass): Long silky tufted flowers on grassy stems from early to mid-summer. Height 60cm (2ft) and spacing 30cm (1ft).
Nigella damascena (love-in-a-mist): Saucer-shaped pale blue flowers surrounded by a ruff of ferny foliage. Seedheads make excellent dried arrangements. Height 30-45cm (1ft-18in) and spacing 15-20cm (6-8in).
Lunaria annua (honesty): White or pale purple flowers in late spring and summer followed by flat, round, silvery seedpods. Height 90cm (3ft) and spacing 20-30cm (8in-1ft).
Papaver somniferum (opium poppy): Single or double flowers in shades of deepest purple, lilac, pink and white, some are blotched at the base. Self seeds easily. Height 45-90cm (18in-3ft) and spacing 25-45cm (10-18in).
P. rhoeas (Shirley poppy): Single flowers have a white base and come in shades of scarlet, pink and white. Height 45-90cm (18in-3ft) and spacing 25-45cm (10-18in).
P. commutatum (ladybird poppy): Scarlet flowers have central black ladybird-like blotches. Self seeds readily. Height 45-90cm (18in-3ft) and spacing 25-45cm (10-18in).
Hardy annuals needing some protection
These hardy annuals will need some protection from frosts, even in milder parts of the UK. Cloches and horticultural fleece should do the job. In colder parts of the country, consider sowing these in pots under glass.
Adonis aestivalis: Ferny foliage and cup-shaped red flowers with dark centres in mid-summer. Height 40cm (16in) and spacing 15-30cm (6in-1ft).
Cerinthe major 'Purpurascens': Deep purple bell-shaped flowers held in a cluster of dark blue bracts in summer; blue-green foliage. Height 60cm (2ft) and spacing 30cm (1ft).
Eschscholzia californica (California poppy): Ferny foliage and cup-shaped flowers of yellow, orange, red or white in spring or summer. Height 15-30cm (6in-1ft) and spacing 20-25cm (8-10in).
Nemophila menziesii (baby blue eyes): Saucer-shaped white or blue flowers in summer, with blue spots on the tips of the petals. Height 15-30cm (6in-1ft) and spacing 15-20cm (6-8in).
Lathyrus odoratus (sweet pea): Fragrant climber with flowers in most colours except yellow from summer to early autumn; best sown in pots. Height 30cm-2.5m (1-8ft) and spacing 20-37cm (8-15in).
Linaria moroccana Fairy Bouquet Group (toadflax): Small, snapdragon-like flowers in pastel shades. Height 15-30cm (6in-1ft) and spacing 7-10cm (3-4in).
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.