Downy Birch
Betula pubescens
Silver Birch
Betula pendula
There are two types of birch in Ireland, downy and silver. The most usual is the downy birch, which like silver birch is a delicate tree with fine branches and small leaves. The springtime flowers are catkins which stay on the tree and contain the mature seed by autumn.
Birch will grow in poor soils, but likes a sunny position. Downy birch is tolerant of wet sites, but silver birch needs good drainage. Birch is typically associated with the Sperrins, growing in peat at the edge of bogs, and on the light sand and gravel soils. It makes a good ornamental garden tree, as it does not grow too large. Like alder, its seeds are popular with small seed-eating birds such as siskin and redpoll.
Collection
Gather ripe catkins when they are dry and are about to disintegrate. Begin testing them in August. The catkins will dry and fall apart releasing the seeds and catkin scales. Collect seeds from native woods. Do not choose birch trees in gardens, parks, or planted roadsides as these are probably imported stock.
Storage
Store the seeds and catkin scales in a cool airy place. They are best stored in a natural fibre sack. Shake the bag regularly to disturb the seeds and encourage air circulation. Recently the CVNI nursery stored a drawer full of birch seed to a depth of 10cm in a dresser in a large shed. In the Spring when it was time to get the seed, two mice jumped out of the drawer – they had had a cosy nest throughout the Winter! However, the seed still germinated.
Sowing
Birch can be raised easily from seed although CVNI experience shows silver birch is harder to germinate than downy birch. The seeds and catkin scales should be sown thinly over the seed bed or seed tray (the catkin scales keep the mice busy!). Roll the seed bed because the seed is very sensitive to seedbed surface conditions. Cover with a light layer of sand to help hold moisture. It must be a very thin layer as the seed is light sensitive and will not germinate if the layer of sand is too thick. Some recommend no coverage at all.
It is essential to keep the seed bed moist throughout the germination period and for two weeks after germination. Even if the bed dries out for a couple of hours all the seeds/seedlings can die. However, birch seedlings grow rapidly when they are given ideal growing conditions.
