Corylus colurna Family: Betulaceae (Birch) Genus: Corylus Species: colurna Common Names: Turkish Filbert, Constantinople Hazel, Turkish Hazel The Turkish Filbert (TF hereafter) is native to South West Europe and Western portions of Asia. Though not native to Minnesota we may well be seeing more of this tree in the future as it is highly urban tolerant and underutilized.
The TF is adaptable to many ecological areas and soils such as clay, loam, acidic as well as alkaline. TF can tolerate lower wet sites and even high and dry ones once established. (Gilman, University of Minnesota)
TF is cold hardy to zone 4 which limits its ideal planting space to the southern portion of our state. However, given the urban heat island effect and warming caused by climate change the TF may well become more common in our state.
As a medium excurrant, i.e pyramidal tree, TF is an excellent substitute for some of Minnesota’s common boulevard trees such as the linden and pin oak. TF is a medium sized tree at maturity with a max height of 40’to 80’ and a canopy spread around 30’ to 50’. (Gilman, UMN, Ohio Plant Facts)
Figure 3, leaves and young fruit
Characteristic of betulaceaebotanical family the wood of the filbert is hard and diffuse porous. Leaves large 4"- 8" long and half so wide (Gilman). The leaves are deep green and provide dense shade. They retain color late into fall and turn pale yellow before dropping. The bark is plate like and tends to look scruffy. The retained catkins, strongly pyramidal form and the flaky bark give TF a significant winter aesthetic. However, neither the fall color nor the spring flowers make much impression. (Ohio PF) The TF produces edible nuts three or more to a cluster enclosed in a spiky shell. The shell ripens from green to brown when mature. (Seiler) The fruits also are a boon to wildlife such as birds and small mammals. That said, the litter of the tree may be a maintenance issue. (Gilman)
Figure 4, male catkins
The Turkish Filbert is monoecious (separate male and female flowers on the same tree) with the characteristic male catkins of the birch family along with small female flowers. The tree is wind pollinated with catkins and flowers occurring at the same time in the spring. (OSU, Gilman) The 50-150 year lifespan of the TF makes it an attractive tree for difficult urban sites. Given the trees natural ability to thrive in urban sites, we should not expect the city life to shorten the natural life span of the tree so long as care is taken after planting to ensure establishment. As of 1993 the US Forest service lists that TF has no serious pest or disease issues. (Gilman) However, new data out of the University of Michigan suggests that TF may be susceptible to our native eastern filbert blight that normally preys on our native filberts such as Corylus americana. (University of Michigan) Japanese beetles also seem to favorite TF. (Ohio PF)
Nuts and husks
Poor transplant survival
Thinned turf grass because of dense shade
Japanese beetles, and maybe eastern filbert blight