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Tuesday, October 28, 2014

Quercus macrocarpa - Bur Oak

The Bur Oak is a beautiful medium to large deciduous tree growing quickly to 50 plus feet with a broad spreading rounded with age. The one large specimen in town has some very untypical features but with the help of Dave Muffly, an arborist and oak specialist, its been identified as a Bur oak or some bur hybrid. I am going with the variable species concept. Oaks are hard to identify, especially without acorns, and this one does not produce any. Also known as Burr Oak.

This specimen from out of town shows a more rounded specimen showing fall color.

The leaves are deciduous, simple, alternately arranged, 6-12" long, obovate shaped, with lobed margins. There is quite a bit of variability in this trait, even among leaves on the same tree.  Dark green upper surface, lower surface with white fuzzy hairs. 

Here you can see some of the variability with more deeply lobed margins.

These shots show more "typical" bur oak leaves.

You can see the nice contrast of the upper and lower surfaces on this tree.

Plants dioecious, males in elongated catkins, females in groups of 3 further back from the  males. On this tree the females start to grow but must not be pollinated, and never grow much beyond a small little bur. These are the males, from another tree. The Soquel tree does not produce any males?

Fruit is an acorn and the name Bur oak is from the cap of the acorn. Also called Mosseycup Oak.

This is a young one, again from another tree elsewhere.

Stems stout, sometimes corky. Brown.

Bark is variable, smooth when young, becoming more vertically fissured with age.

Fall color is yellow to brown but some trees do have some nice red. 

White oaks are a tough group without acorns, even with them. With the variability of leaf shapes on this tree, you can see why I was stumped for a long time, I kept waiting for the acorns, which never showed up. There is a seconded tree below the one on Main St. most likely a seedling and it looks more typical for the species.

Hopefully you will have more luck than I.

3240 N. Main St.

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