Sowing Seeds Outdoors
An effective alternative to artificial seed pre-treatment methods is to adopt nature’s approach taking advantage of microbial, physical and chemical processes over time; that is sow the seeds and wait. This is the approach commercial nurseries often adopt. Woody species that have embryo dormancy are sown in the fall whereas those with double dormancy are sown in early summer; both germinate the following spring. This is the method we recommend as it reliable and non-technical just requiring patience.
- Seedbed preparation is important to propagation of tree and shrub seeds. The seedbed needs to be well drained and ideally a medium textured soil. To aid with drainage it is advantageous to use a raised bed and if needed adding a soil amendment such as sand or peat moss.
- Weed control can be challenge if not addressed early and regularly, seedlings do not compete with weeds so control is important.
- Sowing depth is determined by the size of the seed, generally the 3x rule can be applied, where sowing depth equals four times the diameter of the seed, when seed is expected to germinate shortly after seeding. For fall or summer sowing, when germination is not expected until the following spring, sow seed slightly deeper.
- After sowing, pack the seedbed firmly, water lightly. Covering the seedbed with a thin layer of sand prevents a hard crust from forming on the soil surface.
- It is important to maintain a uniformly moist seedbed until seeds germinate, therefore irrigation may be necessary if there is limited rainfall.
- When germination is not expected until the spring following sowing, weeds can be controlled using non-selective herbicides such as glyphosate. After seed germination, there are few selective herbicides so hand weed control will be necessary
- Depending on species seedlings will take up to two growing season to reach a size where they can be successfully transplanted.