Seed raising 101
Raising plants from seed is a cost-effective way of planting out a garden. Although it’s faster and easier to buy seedlings from a garden centre, growing from seed allows you to choose more unusual vegetables and create backyard biodiversity.
For a seed to germinate and grow into a plant it needs:
Soil or a growing medium Seed-raising mix is ideal; a light soil mix that includes pumice and nutrients that encourage seedling growth.
Moisture Water activates the biochemistry of the dormant seed embryo.
Temperature Plants will germinate at a heat similar to its ideal soil temperature (see our crop growing tips on page 26), although a warmer temperature will speed up growth. Keeping a plant at a consistently warm temperature (in a greenhouse or hot water cupboard) will fast-track germination.
Soaking and scratching
Some larger seeds or seeds with hard exteriors, such as beetroot, need to be soaked before planting to help the plant embryo to break free. These seeds are often from plants native to areas with cooler winters. The tough exterior is designed to protect the seed against harsh temperatures. To soak, submerge the seed in cold water for 12-24 hours. Any longer and the seed will rot. Seeds that might require soaking include beetroot, peas, beans and corn. Some seeds, such as pumpkins and squash, like to be scratched or ‘scarified’ with a nail or emery board to mimic the action of an animal gnawing on the seed. The outer casing is a biological advantage to protect seed from herbivores.
Light or dark
The majority of seeds prefer darkness to germinate. A hot water cupboard is ideal for seed germination. However, some seeds such as lettuce prefer light.
Aosw a g rule, plant a seed no deeper than twice its diameter. As a general rule, plant a seed no deeper than twice its diameter
Seeds planted too deeply will not reach the surface before their food reserves run out.
Fine seeds, such as lettuce or celery, only need to be scattered on the surface and gently pressed into the soil.
To avoid washing away seeds when watering, moisten the soil before planting, then continue to moisten daily. Using a water sprayer wets the soil without overdoing the watering.
Check seed packets for germination time – when seedlings start to emerge, move them to a spot with natural light.
Thinning is winning
When seeds have germinated, thin them out to prevent overcrowding. This is the time to be ruthless. Pull out weaker seedlings to let larger ones thrive. Move seedlings to a bigger pot when the first true leaf emerges.
How to prevent shock
Gradually acclimatize a plant to the outdoors. Move it from a window sill to a spot under a cloche, before exposing it to the elements.
Be careful not to damage root systems when removing a seedling from its tray. Seaweed extract will stimulate root growth.
Planting seedlings in biodegradable peat pots helps avoid root damage. They can be costly, so try making your own (see page 26).