Quercus Robur Tardiflora

An interesting phenomenon which I only became aware of recently is that there are two forms of Quercus Robur, Pedunculate, Common or English Oak.

"Two phenological forms of the pedunculate oak co-occur in the same habitats throughout the species range: the early trees (Quercus robur var. praecox) develop leaves up to 5 weeks before the late ones (Quercus robur var. tardiflora)". "Late trees, which develop leaves asynchronously with eclosion of folivorous caterpillars, avoid the costs of defoliation, which could offset the costs of a later onset of the growing season".

In the UK, Praecox comes into leaf in May and Tardiflora, five weeks later.

I was however becoming concerned with an Oak I dug up last year in the beginning of August, which though having viable looking buds and still green under the bark with the scratch test, only just bud burst yesterday. That's nearer to 8 weeks after my other oaks of the same species.

I know you are supposed to dig up broad leaved tree yamadori just before bud burst in spring, however, Harry Harrington, AKA Bonsai4me states in his experience that the best time to dig up Oak is mid August to September. So I knew I was OK.

Oak in the north of the UK sometimes leaf as late as June, where as in the south as early as the beginning of May. My Oak was collected in Cornwall about as far south as you can get. I live in the midlands, where the tree has been since, so I think this reinforces my theory that the tree is indeed var. tardiflora.

Maybe the later leafing was due to only having been collected last season and the tree was putting on roots first, or maybe it will be normal for this tree, I'll have to wait and see.

So don't be too hasty to throw away those Oak trees that have not come into leaf in line with others as I have done in the past. You may have a Tardiflora.

Oaks cross breed and/or hybridize at the drop of an acorn.

A university recently did genetic tests on the Oak trees on campus and found that ALL were hybrids.

Interesting Billy. I'll do a proper ID of my tree when the leaves are fully open. As for the genetic origins who knows? It would however be interesting to know what causes the late leafing variety to occur, weather it is as simple as a certain percentage in a given population or if there is some kind of symbiosis going on.

Enjoy the Shuttle launch tomorrow, I'm really quite jealous if you get to see them often.

Enjoy the Shuttle launch tomorrow, I'm really quite jealous if you get to see them often.

I live about 15 miles due west of the shuttle pad, I usually watch TV until liftoff then go out to the front yard to watch in the sky. I have been here 45 years so I have seen a few.