How to Grow Trees and Shrubs from Seed.

Many gardeners have been stopped in their desire to propagate trees and shrubs with the discovery that a certain type of seed needs scarifying or another should be stratified. Seed viability, or rather the lack of it and the reasons why some seeds lie dormant until certain conditions are met all add to the feelings of uncertainty and a reluctance to sow. Overcoming these problems isn’t always difficult and the progeny you produce makes the effort worthwhile.

Trees and Shrubs Worth Growing From Seed.

When growing trees and shrubs from seed you are normally restricted to raising species. Cultivars (i.e garden varieties) will not come true from seed. However, certain varieties of mountain ash like Sorbus ‘Joseph Rock’ do come reasonably true from seed. Japanese maples (Acer palmatum species) won’t be identical to the parent plant but you may well get very attractive colour variations.

How and When to Get Seed of Trees and Shrubs.

Collecting your own seed is in many ways preferable to buying it from specialist suppliers. Benefits include the obvious money saving aspects, plus the fact that yu can collect the seed at exactly the right stage of its development. You are able to collect from healthy plants which, because they have grown locally will produce offspring which should do well in your garden.

Autumn is the time to collect seed of many species including Acers (Maples), Aesculus (Horsechestnuts), Qurcus (oaks), Sorbus (Mountain ash), Berberis and Cotoneaster. You will have to be quick to beat the birds to those with berries.

Using Special Treatments to Overcome Dormancy

Some seeds, typically legumes such as Laburnum and Piptanthus develop hard impenetrable seed coats. Although still viable the seeds remain dormant until such time as nature or our intervention allows the seed to soak up moisture. To break this type of dormancy:-

• Soak the seeds in warm water for 24hours prior to sowing, or
• Scarify (rub away the hard coat) with sandpaper.

Many trees and shrubs must experience cold, winter conditions before they will germinate. This means that autumn sown seed stays in the ground for long fruitless periods. To break this type of dormancy simulate winter conditions with the following treatment:

• Mix seeds with moist peat or peat substitute and sand in a polythene bag
• Label the seeds and put the bag in a fridge for 6-8 weeks.

Some seeds like Crataegus (Hawthorn) contain chemical inhibitors which prevent germination as well as hard seed coats. To overcome this double dormancy the seed is subject to a treatment known as stratification:-

• Mix the seed with moist sand and fine bark.
• Place in a vermin proof container outside in a cool place for 18 months.

After this time the chemical inhibitors will have been washed out and the seed coat softened. Dormancy will be broken.

Sow Treated Tree and Shrub Seeds to Invest in a Greener Future

Treated seeds can be sown in trays or pots and put in a cold frame. Once they start to germinate the environment of a warm, but not too warm, greenhouse will speed up growth rate. When the seedlings are big enough to handle pot them up individually into 9cm pots. Growing trees and shrubs from seed may be a long term project requiring some simple all be it special treatments,but it is one in which you are doing your bit for a cleaner, greener future.