Turkey oak is fairly uncommon throughout Exeter but there are some good sized trees in places such as Dix's field (city center) and also the gounds at St Thomas the Apostle Church. From a distance they could be mistaken for English oak but when you get close up the features are very distinct. As the name suggests it is a non-native species of the UK and was introduced in the 18th century. Although it was orginally brought over to to British soil as an ornamental tree there were plans to use the wood for construction much like we do our English oaks. Although Turkey oak does grow faster than English oak the quality of the wood is not as good as English oak. Also the introduction of the Turkey oak also introudcuded pests such as the Knopper gall wasp which is a serious problem for our native English oaks. Despite these problems Turkey oak makes a fine addition to any park or green space.
A fully grown Turkey oak can reach heights of up to 40m but in most cases it will be anything up to 30m. They are deciduous in nature and when in leaf the canopy is fairly open allowing a good amount of light to the ground. The bole (trunk) is typically very straight and upright and the branches are quite slender compared to the English oak. The bark is very distinct both in young and mature oak trees with orange fissures being present. With older trees the bark becomes deeply furrowed.
Around April time the flowers are present. The male flowers are the long yellow / green ones
The canopy of mature Turkey oaks allow a fair amount of light to the ground
As with all oaks the leaves are arranged alternately and have the classic lobbed design. The leaves are usually up to 12cm long and up to 5cm wide. The colour of the leaves is a dark green whereas the underside is pale green. Unlike most oaks the leaves can be quite random in appearance regards their leaf lobes and sinuses. Some leaves will have very large sinuses (the gaps between the leaves) and some are quite close to each other. The leaves are thick and slightly rough to the touch. Ther terminal buds have a whiskery apperance which helps with identification. These 'whiskers' are actually the stipules and remain present throughout the year. The natural hybrid Lucombe oak also shares this characterstic.
The buds are brownish and ovate-shaped. The terminal bud has lots of whiskers
The leaves are dark gree and are usually up to 12 cm long
The flowering is monoecious which means both the male and female flowers are on the same tree but different parts. During April the male flowers (catkins) are present and they really stand out on a windy day. The female flowers on the other hand are harder to spot as they are often hidden by the male flowers and young leaves. The female flowers start off as small red spiky cups which mature into acorns over 18 months. The acorns have hairy / mosry cups which is the same as the natural hybrid Lucombe oak. The flowers are wind pollinated and the fruit (acorns) are typically dispersed by birds and small mammals.
The bark of mature trees is deeply furrowed and contains orange fissures
The acorns are held in hairy / mossy cups
Turkey oak has now become a naturlised tree species in the UK and has been seen in the wild. It is host to Knopper Gall Wasp which is a tiny paratasoid wasp lays its eggs in the female flowers of the tree. Usually the female flowers would develop into the hairy / mossy acorns but if a Knooper Gall wasp has laid eggs they will look very different! The chemical makeup of the developing female flower is changed to suit the growth of the baby wasp. It is still not fully understood how they do this but it is remarkable how such a small insect can dramatically change the design of a tree like this. The baby wasp feeds of the plant tissues and is kept safe in the ever changing 'gall'. The problem is that these Knopper Gall Wasps also lay their eggs on our English oaks which reduces the amount of viable acorns. In 1998 the Ministry of Defence ordered the felling of all Turkey oaks on its UK bases.