Most hardy annuals, biennials and herbaceous plants can be sown directly outdoors where you want them to grow. The secret to success is to prepare a good seedbed, free of weeds and with a fine, crumbly soil tilth.
Sowing seed outdoors is ideal for gardeners who do not have enough room or the conditions and equipment to raise seed indoors. You don’t start seed sowing as early as indoor sowing, in fact, sowing too early when the soil temperature is too low (most seeds need a minimum soil temperature of 7C/45F, but there are many exceptions) will lead to the seeds rotting. This usually means either mid-spring to early summer, or late summer/early autumn for overwintering.
If you can provide the soil and plants with protection, such as cloches or fleece, sowing can begin earlier in early spring. Similarly, regular watering will make it possible to raise 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.
Seed can be sown by one of two methods.
Broadcasting involves simply scattering the seed over the soil. This is usually the best choice when seeding large areas, but it can be difficult later to thin out the seedlings as it’s not easy to differentiate between the cultivated plants and weed seedlings.
To broadcast sow, scatter the seed thinly over the soil and lightly cover them with soil by carefully raking over the area. Aim for a gap of about 13-25mm between seeds.
Then water with a watering can fitted with a fine rose.
Drilling (sowing in drills or rows) is a more precise method and, as you know where the seeds have been sown, you can remove all other seedlings safe in the knowledge they are weeds and thinning out is easier.
To drill, use a bamboo cane, small hoe or the corner of a rake to produce a straight drill (shallow depression) whose depth should be as needed for the species being sown.
The drills should be spaced apart according to the eventual plant height; instructions are usually given on the seed packet.
Water the bottom of the drill before sowing; this is usually better than watering over the top of the seeds after sowing.
Thinly sow the seed in the drill. Don’t be over-enthusiastic, as plants will need thinning to the spacing recommended on the seed packet; 13-25mm apart is usually a suitable distance.
Use a rake to gently cover the seeds with soil, filling the drill back in again. And don’t forget to label the row.
Water the soil or seedlings during dry periods.
Once the seedlings are growing they may need thinning out. This is best done in two or three stages at weekly intervals. The final spacing should be between 10-20cm apart – the lower limit for smaller plants and the upper limit for tall or spreading plants.