A Gardening Journal
The Best Season Ever: The Gold-leaved Poplar in Fall
- Published: November 04 2014
What is the Fall foliage like when a tree's foliage has been colorful in Spring and Summer, too? More of the same? More intense? A different color? Leaves of purple Japanese maples often flare to an astonishing rosy-orange in Fall. What about the Fall foliage of this gold-leaved poplar?
Above, the tree in earliest Fall—September 30—but the weather was still that of Summer. The tree's foliage was as Summer-bright as ever. But now it's November, and Fall weighs heavily on the garden. Light frosts are already in the air, and any week there could be the deeper freeze that would bring the Fall foliage season to an end.
If Populus alba 'Richardii' were going to display foliage that is specifically for Fall, not just the last hurrah of Summer, it's now or never. Below, the tree on the second of November. The gold of the leaves has whitened, with only a few of the very first leaves of the season—those towards the bottom of the entire canopy—changing to a deep gold more typical of Fall. Mind you, "typical of Fall" isn't a compliment here: The white-gold of the upper foliage is a change just in degree from that of the Summer, not in kind. But what Summer foliage! It's far more distinctive.
Compare the two—Summer and Fall—in close-up. Leaves of Summer are infused with more green. Below, those of Fall. They haven't so much changed color as relinquished more and more of the green, allowing the yellow to shine all the clearer. This is the essence of any leaf's transition to its Fall coloring: The loss of the powerful green pigment that is chlorophyll allows underlying pigments to become exposed. With Populus alba 'Richardii', that "underlying" pigment so saturates the foliage that it is extravagantly displayed even while the full complement of chlorophyl is present in Spring and Summer. No wonder the intensity of the pigment amps up even more as the chlorophyll disappears during Fall. The yellow of the brightest of this poplar's leaves is so bright it's almost white. The display is possibly the most intense "yellow" of any Fall foliage.
Back to those lowest-in-the-canopy leaves that turned a more dramatic (but prosaic) deep yellow—and to the existence of the leaf canopy in general. In Fall of 2013, this tree received its first pollarding. (Poplars share with birches a tendency to exude sap profusely when pruned in late Winter or Spring. Pruning in Fall—when the tree is entering dormancy and the motion of fluid is, if anything, downward to the roots—is the answer.) All Winter, then, this poplar was a branchless trunk eight feet high; all the branches of the canopy were grown from May into October.
Although, yes, a branchless trunk from December through April is a grim sight, the warm-weather benefits of pollarding are so striking that the Winter-long decapitation is worth it. First, the overall size of the tree is controlled. Second, because all the branches emerge, simultaneously, from just the top few inches of the trunk, there is little competition among them. Instead of one branch gaining dominance and, thereby, continuing to shape the tree into its natural profile of a central trunk with distinctly shorter side branches, the growth of all the new shoots is a comparative free-for-all. And, so, the shape of the canopy is a dense sphere.
Pollarding often affects the size and behavior of the foliage on the resultant stems, too, not just the stems themselves. (Leaves of a pollarded empress tree are larger; leaves of pollarded smoke bushes aren't much larger, but they continue to be produced all season, and with maximum depth of color.) What might the affect of pollarding be on the foliage of this poplar?
Not much: For such a supremely colorful plant, pollarding seems to change overall shape—that striking rounded canopy—far more than foliage hues in Summer or Fall. Those few butter-yellow leaves at the bottom are a minor distraction from the ever-increasing brilliance of the whiter-and-whiter gold foliage of the upper and outer portions of the canopy. If this tree were a singer, its song would be the same Spring through Fall—just sung higher and higher as the weather turns chilly.
Here's how to grow Populus alba 'Richardii', as well as close-ups of its remarkable gold and white foliage.