Purest of Noble Trees

By Lynne Pieri-Finn, Fairfax Master Gardener Intern
The real voyage of discovery consists of not in seeking new landscapes but in having new eyes. — Marcel Proust

white oak

White Oak

When I’m out walking my dog, I like to look around at trees and shrubs. I have my favorites, I’ll admit, like Pieris japonica. I didn’t know all that much about trees, though, so I took a class at Northern Virginia Community College called Woody Plants. The class covered over 140 trees and shrubs. We looked at leaves, flowers, fruit, stem, bark, fall color, soil and sun preferences and habit/shape.

With each tree I learned, I had a new favorite. I loved the oaks, so we’ll talk about that in this article. There are whole books on oaks alone. If you cannot identify an oak right away, look at the leaves. Most are lobed, sometimes deeply. The deep indentations in the lobes are called sinuses and may be deeply cut to the midrib or not. Good examples of lobes deeply cut or not are the Southern Red Oak (Q. falcata) and the Chestnut Oak (Q. montana). Of course, the Willow Oak (Q. phellos) is an important exception; its leaves are long and entire, like a willow leaf.

Pin oak

Pin Oak

All oaks have acorns. After I started the course (and probably before, since I still find acorns in the pockets of jackets I haven’t worn for a while), I gathered interesting acorns and leaves to analyze and compare. Some acorn caps look like little French berets such as on the Pin Oak (Q. palustris); others have caps that nearly cover the nut like the Overcup Oak (Q. lyrata). The nuts of Southern Red Oak (Q. falcata) can be striped; White Oak (Q. alba) nuts are a beautiful Hershey Kisses brown. Some nuts are long, like the Northern Red Oak (Q. rubra) and others are short like the Bear Oak (Q. ilicifolia).

By the way, 2019 was what they call a mast year for oaks and other nut-producing trees. Mast years are high-production years. Acorns were everywhere, and the squirrels had a nice feast. Early humans also ate acorns; in fact, it was one of the main staples of their diet. They leeched out the tannins and made the paste into flour or a jelly-like cake. In Korean stores, you can still find it. It is called Dotori-muk. Oaks ranged from Asia, through Europe and the Americas.

Oaks are in the Fagaceae family. All oaks have the genus Quercus. There are two main groups of oaks: white oaks and red oaks. Let’s start with differences:

White Oaks Red Oaks
Rounded tips of leaves Bristle-tipped leaves
Rounded buds, reddish brown Pointed buds
Acorn cap surface mostly smooth Acorn cap surface wooly
Acorns mature in one growing season Acorns mature in two growing seasons
Squirrels like acorns (staple of early human diet) Acorns taste bitter
Grayish, scaly, soft bark Hard, dark-colored bark
Wood hard and strong Wood somewhat hard

Similarities of course include the acorns, the oppositely arranged leaves, and the male and female flowers on the same tree (monoecious). The male flowers consist of dangling catkins. The female flowers are very small and are hard to see with the naked eye, unless you have a ladder and a magnifying glass, and you catch the flowers at the right time.

Wind-pollinated flowers on trees do not necessarily have to be conspicuous. Flowers that need pollinators need to attract them, hence, big and conspicuous. The cones on conifers, also monoecious, are mostly near the top of the tree to catch the wind.

With all this wind-pollination going on, it is easy for different species of oaks to cross-pollinate. However, the vast majority of oak trees are still recognizable to species. This shows us that hybridization tends not to lead to new species formation very often. Part of the reason for this is that some hybrid oaks do not reproduce — they are as sterile as a mule. Interestingly, this only happens with the red oak group. Identification can stump the experts.

Red oak leaves

Red Oak Leaves

Also, some oaks have differently-shaped leaves on the same tree. Oaks with lobed leaves (which includes most species) usually have more deeply and more narrowly lobed leaves where exposed to intense sunlight; in a forest this is usually only near the top.

Rule of thumb: rounded lobes = white oak; bristle-tips = red oak. Look at the differences between the Post Oak (Q. stellata) and the Northern Red Oak (Q. rubra). Additional red oaks in our area are the Southern Red Oak (Q. falcata), the Blackjack Oak (Q. marilandica) and the Black Oak (Q. velutina), which is not “red” at all but has bristle tips. Some white oaks you’ll see in our area are the Swamp White Oak (Q. bicolor), the White Oak (Q. alba) and the Durand Oak (Q. sinuata).

Black Oak

Black Oak

There are some tremendous Willow Oaks in Morven Park in Leesburg, which brings me to my next point. If you plan to plant an oak, give it a large area in which to grow and spread its roots. A better street tree specimen is the Pin Oak (Q. palustris). It has a distinctive shape: branches at the top go skyward, in the middle they are horizontal and at bottom they hang down slightly. English Oak (Q. robur) has a cultivar called ‘Fastigiata’ and it is tall and narrow.

In fact, there are cultivars of many types of trees which look nothing like the original.

Now that you are on your way to recognizing trees on your daily strolls, say hello, and like good neighbors, it is nice to know their names.

Resources
The Tree Book by Michael A. Dirr and Keith S. Warren
Seeing Trees by Nancy Ross Hugo, with photos by Robert Llewellyn
Remarkable Trees of Virginia, by Nancy Ross Hugo and Jeff Kirwan, photography by Robert Llewellyn

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