Red Oaks, Extraordinary at any Size

Let an acorn sprout and in sixty years or so, you, too, could be looking at a mighty oak. Here is one of a slew of red oaks thriving along the Niagara River, which connects Lake Erie with Lake Ontario. I was fortunate to stroll past such monarchs, one after another, on a morning walk during an annual trip to theater festivals in Ontario.


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The river banks are steep bluffs easily thirty feet high, so trees at the crest, like this one, usually enjoy plenty of sun on the side facing the water. With parkland on the inland side, too, this tree has any oak oak's preferred exposure: Like lilacs, these supremely hardy plants crave full sun, and don't care at all if that also means full exposure to sweeping winter wind.


Quercus rubra is easy to establish in a garden. But how many of us can welcome a tree with a mature shade-providing canopy seventy feet or more wide? Not me: My garden is large, but already packed with sun-lovers. Happily, other talents than size make a red oak a possibility for full-sun spots in gardens of any size.


Below, one of a pair of youngsters flanking a walkway heading west from my back door.


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The beds on either side of the walk are prime spots: nicely mounded and therefore well-drained, with full sun from mid-morning to dusk. And they could scarcely be more powerfully focal, with southern magnolias trained to the roof as their backdrop, then countless beauties crowding the space in front.


Planting what could become gigantic trees in the midst of a lapidary display of sun-lovers would be catastrophic. But my red oaks will never become larger than slender shrubs. No, these aren't dwarf cultivars—which, to my knowledge, don't exist. I will keep these red oaks dwarf through annual pruning.


I'm taking my cues from the oak cousins, the beeches and hornbeams. As free-range soloists, they can also become gigantic. But these monumental trees also thrive when pruned into hedges, topiary, and espaliers a tiny fraction the size. Why not prune a red oak? In my case, the shapely goal will be a standard with a head perhaps a yard wide on a trunk that's free of growth for four to six feet. In other words, a mature tree that is just eight or nine feet high and only three feet across.  


Free-range red oaks can be sixty to a hundred feet high, with canopies nearly as wide. In comparison, my pair of red oak standards would be lilliputian. But the bravado of forming such dramatically dwarfed trees, let alone from a species that is rarely trained, is just the conceptual thrill. The visual excitement will be year-round; even better, it will peak in the cool months. Could any garden have too many plants that claim as much?


Like beeches and hornbeams, oaks that are either young or remain compact at any age retain their fall foliage throughout the winter. These thick pointy leaves turn red in October—this is a red oak, remember—but then progress to an attractive tan that is often described as the color of pigskin. Most of the leaves remain on the branches through late winter and even into spring, until emerging new growth pushes them free.


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I've written many times about plants that retain fall foliage through the winter; this talent is termed marcescence. Here's a look at my hedge of American beech in winter; here's a look at my quartet of columnar hornbeams, whose marcescent display is, as is typical, affected by how they are pruned.


If pruning my red oaks as standards enhances their ability to display marcescent foliage, it will be a victory that is both conceptual and visual. And because oaks can live for centuries, spectacularly enduring.



Here's a look at another of our majestic native oaks, Quercus alba. It also retains its Fall foliage through the Winter. Both species are seriously hardy—to Zone 3, so hello Manitoba! Quercus alba can be difficult to establish outside of undisturbed native-woods habitat, requiring a complex symbiosis with indigenous soil microbes; I have failed so far to establish it in my garden, despite gardening organically and using extremely wildlife-friendly practices. Quercus rubra seems to establish readily; so far so good. I'll profile this latter species in 2018. 


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