I love the idea of growing a pocket forest (a small, densely planted area of trees and shrubs) from seeds collected in local woodlands. Could you please share any useful tips on getting them to germinate? A Fitzgerald, Co Wicklow
What a great idea! So, to answer your question, by far the best approach when it comes to encouraging any seed to germinate is one that tries to replicate the conditions that the particular species would naturally receive in the wild in its country of origin.
This shouldn’t be too difficult when it comes to Ireland’s 28 native tree species such as sessile oak, pedunculate oak, mountain ash or rowan, downy birch, silver birch, blackthorn or sloe, wild cherry, bird cherry, elder, hazel, alder, holly, yew, hawthorn, Scots pine, crab apple, willow, strawberry tree and spindle.
But bear in mind that while all the above are native, their preferred growing conditions still vary quite widely according to the particular species. As for non-native species, these can be a little trickier as a rule, although some, such as beech, have long ago become naturalised in Ireland and their seed will typically germinate quite freely.
Autumn is an excellent time to collect the ripe seed of most trees. Just as for their growing conditions, optimal conditions for germination vary according to each species but most benefit from a process known as stratification. This sounds complex but is simply the process of mimicking the effects of winter in order to break dormancy and ready seeds for germination.
Some species are best stratified straight away. Others are best stored in a cool, dry, rodent-proof place over winter using a labelled cloth bag before being stratified early next spring in preparation for sowing under cover of a glasshouse, polytunnel or cold frame. In some cases, you’ll need to first carefully extract the ripe seed from the fruit (for example, in the case of crab apples and rowan berries) using a process known as maceration.
To stratify seed, place it in a tray or pot between shallow layers of damp horticultural sand mixed with compost/leaf-mould. Then put it in a cool place outdoors, out of direct sunshine for anywhere between several weeks to up to 18 months depending on the species. Keep watered as required and keep a beady eye out for early signs of germination. Once you spot the latter, the germinating seeds can then be very gently removed from the pot and individually sown into small pots.
Bear in mind that the smaller the seed, the more likely it will need to be sown very shallowly to allow exposure to natural daylight as an essential trigger for germination.
For specific advice on propagating different native tree species from seed, see the excellent websites of the Tree Council of Ireland and the All-Ireland Pollinator Plan. For advice on both native and non-native species, see teagasc.ie. For advice on establishing a pocket forest, see pocketforests.ie
