The Royal Horticultural Society Horticultural Advisory Leaflet Number 217 February 2000
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 Hardy Annuals
Hardy Annuals (H.A.) are sown directly in the soil where they are to grow. They will withstand frosty conditions without protection, whereas Half Hardy Annuals (H.H.A.) need to be sown and grown on under glass, being planted out only in late spring when there is no further risk of frost or the likelihood of cold weather. Position Most annuals need a sunny open position and will be slower to come into flower, and flower less freely, in shady situations. Soil Annuals tend to be most successful on medium to lighter soils which warm up early in the spring. They can be slow to germinate, establish and grow away on heavier, poorly drained soils which are cold. Such plants are not as successful on rich soil as this encourages lush growth and fewer flowers. Soil preparations Start in the autumn. The area to be sown should be dug over roughly, then left over winter for the weather to break the soil structure down. In spring, lightly fork the area through, removing any weeds, then tread lightly to help settle the soil. Sprinkle 70g per m2 (2oz per sq yd) of a general fertiliser, such as Growmore, over the area and rake in, levelling the soil to make a good sowing surface. Omit fertilisers from rich soils. Marking out Use a plan prepared during the winter marking out the positions for the different varieties. Do this by scratching the soil with a cane or by sprinkling sand to outline each sowing area. Sowing Sowing can begin from late March to May depending on the area: early sowing in Southern England, later in the Midlands and North. In the milder gardens of the south and west, sowing may begin early and be spread over several weeks; in colder northern gardens begin sowing later with fewer successional sowings. A few hardy annuals, eg; Eschscholzia, can be sown in early autumn overwintering as young plants to give earlier flowering the following spring. Method If conditions are dry, water thoroughly using a watering can and fine rose. Draw out drills using the corner of a Dutch hoe blade. Vary the direction of the drills for each variety to avoid a uniform and regimental appearance. Sow in drills 0.5–1.5cm (¼–½in) deep, depending on size of the seed. Smaller seeds need only be lightly covered. Spacing between drills depends on the eventual size of the plants. Space out larger seeds by hand. When sowing very small seeds first add some fine sand to the packet, shake well, then sow. This helps towards achieving more even distribution. After sowing rake soil into the drills, firm gently with the back of a rake. Where necessary protect from birds, cats or rabbits by placing wire netting or plastic fine mesh netting over and around the area. Another method of sowing is to scatter or broadcast the seeds over the appropriate area, lightly rake in and then sieve some compost over them to cover to 0.5–1.5cm (¼–½in). Then treat as above. Thinning As seedlings grow they should be thinned, as soon as large enough to handle, to one quarter of their final distance apart. After a week or two thin again, to half the final spacing and later to their final growing distance. If lifted carefully with a small hand fork, thinnings can be used to fill any gaps or to make other plantings elsewhere in the garden. Staking Some kinds of annuals may need support. This can be given by pushing twigs or twiggy brushwood between them when the young plants are 7–12cm (3–5in) high. Taller kinds can be given individual support, using canes and twine. Aftercare Keep down weeds, by means of careful light hoeing in early stages of growth – later by hand weeding. Water in dry weather, checking regularly during the critical
stages of germination and seedling establishment to ensure that the seed bed does not dry out. Once well established water thoroughly and regularly at 10–14 day intervals during periods when there is no appreciable rain. Removing dead heads will often prolong flowering.
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