Seed: sowing hardy annuals in spring

Easily grown from seed, a vast choice of hardy annuals is available to offer long-lasting flowers during the warmer months. These fast-growing plants provide an easy and cost-effective way to give naturalistic planting, plug gaps and fill the border with a summer full of colour.

Seed: sowing hardy annuals in spring

Quick facts

Timing Spring, late March to May
Difficulty Easy to moderate

Suitable for...

Spring sowing is suitable for annuals (plants which are sown, flower and die in one year) that tolerate light frosts. A spring sowing differs from an autumn sowing in that it tends to produce a later flowering display. Seed catalogues often use the abbreviation (HA) to describe hardy annuals.

It should be noted that although these plants usually withstand frosty conditions without protection, some hardy annuals may need covering with horticultural fleece or a cloche when a heavy frost is forecast.

Hardy annuals to try

The following are some suitable hardy annuals requiring no protection unless the winter is particularly severe:

Old favourites:

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.
Eschscholzia californica (California poppy): Ferny foliage and cup-shaped flowers of yellow, orange, red or white in spring or summer.
Limnanthes douglasii (poached egg plant): Masses of dainty cup-shaped yellow-centred white flowers from summer to autumn.
Nigella damascena (love-in-a-mist): Saucer-shaped flowers in shades of blue, rose, pink or white, surrounded by a ruff of ferny foliage. Good for cut flowers and seed pods can be dried for winter decoration.
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.
P. rhoeas (Shirley poppy): Single flowers have a white base and come in shades of scarlet, pink and white. 
P. commutatum (ladybird poppy): Scarlet flowers have central black ladybird-like blotches. Self seeds readily.

Something different:

Agrostemma githago ‘Milas Purple Queen’ (corn cockle): With purple-red flowers.
Briza maxima (quaking grass): With creamy-white shimmering spikelets, ideal for dried arrangements.
Cerinthe major var. pupurascens: With fleshy blue-green leaves and dark purple-blue flowers.
Cleome chilensis: Has neat palmate foliage and white flowers.
Moluccella laevis (bells of Ireland): With fragrant green flowers are ideal for flower arranging.
Nemophilia menziesii ‘Penny Black’: With masses of attractive deepest-purple flowers, edged white.
Nicandra physaloides (shoo-fly plant): With blue bell-shaped flowers and papery Chinese lanterns.
Orlaya grandiflora: Has distinctive ferny foliage. Lacy pure-white flower umbels are ideal for flower arranging.

Good for wildlife

As well as being ornamental, some hardy annuals will provide nectar and pollen for bees, butterflies and other insects. Phacelia tanacetifolia, pot marigolds, cornflowers and sunflowers are all suitable. Those with attractive seedheads such as Nigella and poppies can provide a valuable food source for birds.

For additional varieties, see Seed: sowing hardy annuals in autumn

When to sow hardy annuals

Sowing can begin from late March to May as the soil begins to warm up (often indicated by the emergence of weed seedlings). It may begin earlier in milder gardens of the south and west; in colder northern gardens sowing may be later.

Annuals do best on light soils. These are not usually too fertile and have the advantage over heavier soils, of warming up earlier in the spring. Germination is slower on heavier, poorly drained soils which remain colder for longer after winter.

Lush growth and fewer flowers may result on rich soils. It is worth noting, however, that cornfield annuals tolerate a richer soil and make a good alternative to a wildflower meadow where soil is too fertile.

How to sow seed

Weed the bed, level the soil with a rake and tread lightly before sowing.

Direct sowing can be done by broadcasting (scattering seeds over the surface). The main disadvantage of broadcasting is that you cannot easily tell weed seedlings apart from your sowings. Alternatively, drills (shallow grooves), can be planned and marked out to produce drifts of flower for a natural appearance.

Refer to seed packets for the best time to sow and depth for seed planting.

Aftercare

Once plants are growing strongly, attention will be needed to:

  1. Keep down weeds with light hoeing or hand weeding
  2. Water in dry weather, regularly checking to ensure seed bed does not dry out during the early stages of germination and seedling establishment
  3. Once well established, water at 10-14 day intervals during dry spells
  4. Deadhead to prolong flowering
  5. Thin out self-sown seedlings and transplant to fill gaps elsewhere in the garden

Problems

Under glass, hardy annuals can suffer from damping off of seedlings. Powdery mildews may be troublesome.

Slugs and snails may damage vulnerable seedlings. Aphids may be a problem for young shoots. Birds such as pigeons can be a nuisance where seeds are not covered with fleece.

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