Many vegetables, annuals, biennials and herbaceous plants can be grown from seed sown outdoors. The secret to success is to prepare a good seedbed, free of weeds and with a crumble-like soil-surface texture.
Many vegetables, annuals, biennials and herbaceous plants can be grown from seed outdoors. Ornamental examples include Centaurea cyanus (cornflower), Digitalis (foxglove), Eschscholzia (Californian poppies), Helianthus annuus (sunflower), Iberis umbellata (candytuft), Limnanthes douglasii (poached egg flower) and Tropaeolum majus (nasturtiums). Vegetables such as beans, carrots, onions and peas can also be grown outside from seed.
Sowing seed outdoors, directly into final growing places, is ideal for gardeners who do not have much room to raise seed indoors in trays or propagators. You also don’t need to start seed sowing as early in spring as when you sow outdoors. You can scatter seed of ornamentals in free drifts to achieve a natural-looking distribution, or sow vegetables and cutting flowers in clearly defined drills to make weeding and thinning easier to carry out.
When to sow seed
As long as the soil is warm and moist, seed can be sown and it will germinate quickly. In practice, this usually means either mid-spring to early summer (April-June), or late summer (September). If you can provide the crop with protection, such as cloches or fleece, sowing can begin in early spring. Likewise, regular watering will make it possible to raise rows of seedlings in the height of summer.
Always refer to the seed packet for the best time to sow, as it does vary with plant type.
How to sow seed
Sowing seed is very straight forward – just think of how many plants scatter their seeds and they grow where they land as soon as it is moist and warm. However, for the best success, this is the best way to sow:
- Beds should be dug over in advance to allow time for the soil to settle. New beds can benefit from double digging, but turning the soil over to a spade’s depth is usually sufficient
- Cover over the roughly dug bed with plastic or a double layer of fleece to suppress weeds and, in early spring, to help warm up the soil
- When you are ready to sow, uncover the bed. Use a rake to level the surface and create a crumble-like tilth. Then pick off any remaining weeds and debris
- Place a cane or stake across the bed and lightly push it into the surface. This will create a straight drill (shallow depression) whose depth should be as directed on the seed packet. The drills should be spaced according to the instructions on the seed packet
- Alternatively draw out drills with a small hoe or the corner of a rake
- Add water to the row before sowing. This is usually better than watering over the top of sown seeds
- Thinly scatter the seed into the bottom of the drill. Don’t be over enthusiastic, as plants will need thinning to the spacing recommended on the seed packet. A finger width apart is usually right for small seeds
- Use a rake to gently cover the seeds with soil, filling the drill back in again
- Before you forget where the row is and what you’ve sown, place a label in the soil at one end.
- Cover the patch with a single layer of fleece. Use a spade to push the edges of the fleece into the ground to ensure it doesn’t blow away
- Remember to water in dry spells
Packing down of certain soils under heavy rain can cause a cap of hard compacted soil that dries to a crust thorough which seeds can not emerge. Prevent this by covering seeds with potting media such as peat-free multipurpose compost.
Other problems include:
- Pigeons and other birds can be a pest where seeds are not covered with fleece
- Occasionally, seedlings can fail to emerge, or keel over soon after emergence in wet weather. This is known as damping off
- Likewise, slugs and snails eating young seedlings can be a problem