Oak Pedunculate
Quercus robur
Sessile
Quercus petraea
Once widespread throughout Ireland, oak has been harvested for its fine timber for centuries, and little has been replaced. Truly native Irish oak may be hard to find, but there are small woods in most counties. The traditional Irish oak is the sessile oak, but the pedunculate or English oak is also considered native.
The male flowers of oak are borne on rather inconspicuous catkins which come out just before the leaves, but the seeds – acorns – are far more obvious. Oak trees do not produce a good crop every year, so it is worth gathering plenty in a good year.
Like other trees, the best oaks grow on the best soils, but Irish oak will tolerate thin soil on rocky ground and needs a well drained site. The English oak grows on heavy lowland soils and can withstand wet soil in winter.
Oak is an extremely valuable wildlife tree for the whole of its long life, supporting the largest number of insect species of any native tree. They grow into wonderful huge trees, which may live for hundreds of years.
Collection
Remember there is not a good crop of acorns every year, so be patient. Acorns can be collected while still on the tree if they are ripe. They can be picked when the acorn has turned brown and comes away from the cup fairly easily. When the seed is fully ripe there is usually a big fall of seed. It often happens on the morning following the first frost. In tree nurseries you can often hear the question “has the big fall happened yet?”
It is also important to note that with oak (as with hazel and beech) there is a gradual fall of non-viable seed before the “big fall”.
Storage
Sow straight away if possible as stored seed may lose viability. If necessary store in a cool, well ventilated place in a hessian bag. Protect against being eaten by mice.
Shake the bag gently, every so often, if collection is on a large scale to prevent the acorns heating up. It is also very important that they are not allowed to dry out as they lose viability rapidly. In the New Year check every so often to see they are not beginning to shrivel. If the first signs are observed the seeds should be sprinkled with water to keep them plump until they are sown in the spring.
Sowing
One method is to sow acorns soon after collection to a depth of 10cm, leave them over Winter, and then in March rake off the top 5cm to leave a 5cm covering. This protects them from being eaten, and they should shoot in May. Otherwise store and plant in late March. Allow plenty of space for the seedlings which have big leaves even when very young.
