Nature Notebook: Oak

Northern Red Oak (Quercus rubra): Sketches of winter tree, fall tree, leaves and acorn

All the art and photos are by me!

Types of Oak

Oaks are found worldwide. Asian oaks often look quite different from North American oak. Common features include acorns and lobed leaves. North American oaks can be divided into the white oak group (rounded leaves), which includes the white and black oaks, and the red oak group (pointed leaves), which includes red and pin oaks.

Oak Identification

Oaks are large, solid deciduous trees with heavy, opposite branches that grow straight out from the trunk at a right angle and then curve upward (or sometimes downward, or sometimes in weird directions).

Leaves

In North American oaks, the leaf is long and lobed. (Asian oaks tend to have palmate leaves.)

The red oak group has pointed lobe tips with small bristles, and the white oak group has rounded lobe tips without bristles. The way I remember this is that red oak leaves are pointed like fire and white oak leaves are rounded like clouds. (Both species’ leaves are green in summer and red in the autumn, so don’t rely on color.)

I can’t consistently tell the difference between the leaves of different Red Oak Group species, but I think the ones that are fuller and have a lot of lobes tend to be Northern Red Oak, while the ones that are skinny with deeper indentations and fewer lobes are more likely Pin Oak.

Oak leaves are bright green in the summer and turn exciting red/orange colors in the fall. While not quite as bright and showy as the maple, they tend to be very colorful.

Oak leaves in autumn. November 2020 in Cambridge, Massachusetts.

Leaves deteriorate slowly, and in winter the dry leaves are quite tough and leathery. The tree tends to retain at least a few of the leaves through winter. (Beeches also do this, but the leaves are shaped like ovals, while oaks are lobed.)

Dried oak leaves clinging to the tree in winter. March 2019 at Arnold Arboretum, Jamaica Plain, Massachusetts.

Flowers

Oaks flower in the spring and have non-showy strings of greenish flowers.

Fruit/Seed

Oaks have acorns!

Acorns growing on an oak twig. September 2020 in Cambridge, Massachusetts.

Acorns are so cute. They look like they’re wearing little berets.

Hand holding a small acorn. September 2020 in Cambridge, Massachusetts.

Bark

Oaks in the red oak group have “ski trail” bark – parallel furrows. In younger trees, they’re reddish. Meanwhile, white oaks have light-colored “checkerboard” bark that’s broken horizontally and vertically. (Thanks to A Beginner’s Guide to Trees of the Northeast by Mark Mikolas for this bark terminology!)

Interesting Facts

Those indestructible leaves you’re raking up all winter are usually oak. The tough leaves beneath the tree form a nice warm home for other plants and animals through the cold season. If you look amongst the oak leaves at the base of a tree, you can sometimes find wintergreen growing there!

Wintergreen growing amongst oak leaves. March 2019 at Franklin Park, Jamaica Plain, Massachusetts.

Painting Tips

Oaks can grow very tall and the trunks and branches are heavy and solid. Branches tend to grow out of the trunk (or out of each other) at right angles and then curve up.

Heavy, curving limbs of an oak. March 2019 at Arnold Arboretum, Jamaica Plain, Massachusetts.

While I tend to think of oak as a background tree because it’s so common where I live, it’s truly an impressive giant and a wonderful late fall showstopper. I hope you enjoyed getting to know the oak with me.

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