A Gardening Journal
The Best Season Ever: Young Stems of the White-Poplar Pollard
- Published: December 02 2015
With such bright gold foliage Spring through mid-Fall, why this tree is called a white poplar isn't clear until weather cold enough for leaf-drop. Then the young stems' bark shines, and the tree's Latin name, Populus alba—literally, white poplar—is finally spot-on.
In the picture below, notice that the bark is whiter on some stems than on others. Plus, that of the newest portions of all stems—the tips and middles—is brighter than that of the bases.
The bases of the stems are more tan, while the trunk is gray.
The common name of white poplar, then, refers to just the upper sections of the newest growth—that formed in Summer of that very same season, in fact. Even the bark at the base of those first-year stems—which was formed in the Spring—has already changed by early December from white to tan.
In total, Summer and Fall are six months long. If bark on stems even seven or eight months old isn't as showy, stems from the previous years are truly not helpful. On this basis alone, white poplar is a terrific candidate for radical pruning to remove as much older growth as possible. It also responds enthusiastically, which is the other essential condition needed to make drastic pruning possible.
Each year, I prune all stems of my tree back to the same top foot of its short trunk, a practice known as pollarding. This is why even the thickest, oldest stems in this tree aren't more than a few months old: The entire canopy of branches—some of whose stems are eight feet long—is formed afresh each season.
The norm for shrubs and trees that respond well to such severe pruning is that their Winter display of bark is effective right through until Spring. (See these colorful examples of pruned linden, hardy orange, ash, and caragana.) The cold-weather display of a pollarded Populus alba, alas, is comparatively brief. This isn't because the stems' color is lost as Winter progresses. Rather, the quirk of poplars is that they produce so much sap late Winter into Spring that pruning isn't recommended later than Fall, so that cut stems have plenty of time to callus over.
But, darn it, the only way to maintain a dense head of young-as-possible, white-as-possible twigs is by this same pruning. And the trees are so fast-growing that if it isn't done each year, the display will be muddied by the bark of the then-"ancient" stems from the previous year. So there's little to be gained by pruning every other year to enjoy a Winter-long display in the intervening year: The display will be second rate.
Though the show of a pollarded white poplar is just for Fall, then, it's still worth it (in my book, at least) to have a canopy-less knob at the top of the freshly-pollarded trunk all Winter. First, brevity is central to most peak moments. If weeping cherries were in flower for months not days, would there be so many festivals to celebrate them? So much art and poetry to memorialize them? The next time you're in the tropics, check how long it takes you to stop marveling at the hibiscuses. They are ever-blooming—but, after a day or two in paradise, do you still care?
Second, the look of a pollarded trunk is, itself, both dramatic and telling: The gardener made the choice to grow a plant that benefits from such bravura pruning, and didn't hesitate to do it at the right season.
I'll try to pollard this Populus alba at the Winter solstice, December 22. It is the shortest day of the year, and marks the last day of Fall and the first of Winter. Stay tuned for the startling change in this tree's look.
Here's a look at the luminous Fall foliage of this particular form of white popular, the gold-leaved cultivar Populus alba 'Richardii'.
Here's how to grow Populus alba 'Richardii', as well as close-ups of its remarkable gold and white foliage while still "just" in its warm-weather hues.