A Gardening Journal

Gold-leaved White Poplar

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The leaves of 'Richardii' poplar are an exceptionally bright yellow all season long. This is the only poplar to try in a garden setting; leave the rest to native stands in the Rockies or mountains of Europe.

 

The brilliant yellow of the leaves is matched by the pure white suede-like covering of the stems.

 

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Even the backs of the leaves are pure white—hence the Latin name, Populus alba, as well as the common, white poplar.

 

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Although the growth rate of 'Richardii' has been slower than the speedy white popular species, the tree can still be cut back to stubs annually. As in the photo below, new growth can lengthen to five or six feet by September and is, if anything, even brighter and more startling than when the tree is left to grow free-range.

 

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Even when the tree is out of leaf in the cold months, Populus alba is easy to identify. The smooth grey-green bark of the trunk is pierced by hundreds of diamond-shaped openings that reveal the tan and black of deeper layers.

 

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See "How to handle it: Another option—or three!" for strategies to welcome yellow-leaved white poplar into gardens that are compact as well as immense.

 

Here's how to grow this unusually colorful tree:

Latin Name

Populus alba 'Richardii'

Common Name

Gold-leaved white poplar

Family

Salicaceae, the Willow family.

What kind of plant is it?

Deciduous tree.

Hardiness

Zones 3 - 8.

Habit

Upright. 

Rate of Growth

Surprisingly slow.

Size in ten years

An upright tree twelve to twenty feet tall and eight to twelve feet wide.  I grow two individuals, both in very nurturing circumstances.  Even so, both were startlingly slow for the first six years.  Only in adolescence, apparently, does 'Richardii' pick up speed.   

Texture

Medium in and out of leaf.

Grown for

its foliage: Primrose yellow all season long.  The backs of the leaves are a pure white all season long, thanks to a durable pure-white fuzziness known as indumentum.  Other species with cultivars with showy indumentum include Magnolia grandiflora, whose indumentum is typically cinnamon; and Rhododendron yakushimanum, whose indumentum is usually silver.  I crave Rhododendron bureavii, whose young foliage is, perhaps, more thickly clothed than any other plant, making the bush seeming to be covered with immense fuzzy blossoms that emerge white, then age to cinnamon.    

 

its young stems:  These are covered in the same white indumentum as the leaves.  The indumentum lasts all season on the stems as well.

its tolerance of wet soils.  Poplar roots are, famously, ever in quest of water.  Trees tolerate locations with seasonal flooding as well as poor drainage year-round.

Flowering season

Populus alba 'Richardii' flowers in early Spring, before the leaves emerge.  As is typical for poplars, it produces pendulous catkins.  Trees are dioecious; catkins on male trees are two to three inches long, three to four inches long on female trees.  'Richardii' is usually pruned to control size and enhance production of new foliage and twigs, and the pruning removes wood old enough to flower.  See "How to handle it" below.

Color combinations

The tree's coloration—strong yellow and yellow-green leaves that contrast delightfully with the snow-white young stems and the backs of the leaves themselves—is so strong and distinctive that you should think twice about introducing additional colors even though, in less saturated circumstances, they would harmonize well.  Medium and dark green are always safe, as would be plants with white components that are truly as Oxydol-white as those of 'Richardii'; near-whites will look dirty.  Burgundy and medium-to-dark blue would also be possible, but because the poplar's growth is not just bright, it's also comparatively monochromatic, the juxtaposition could seem strident instead of inspired.  See "Plant partners" below.

Plant partners

Populus alba 'Richardii' is combined on the basis of both habitat—near neighbors need to be at home in the same moist circumstances that the poplar prefers—as well as coloring.  Whether grown free-range, or as a coppice or pollard, the tree's stems are typically broadly upright, and so are easy to combine with neighbors of almost any height. 

 

In truly wet circumstances, why not underplant with ferns?  Their fresh-green fronds will extend the zone of brightness of the poplar's leaves and stems right to ground level.  In moist but not sopping soil, Ilex glabra would be terrific; it is one of the few broad-leaved evergreens that tolerates somewhat poor drainage.  Its round leaves and mounding habit are similar to that of boxwood, which would be a risky partner in that it doesn't tolerate poor drainage.  The leaves' dark green is excellent color contrast, too.  If there's well-drained ground at the back of the poplar, the dark needly green of yews (either free-range or hedged) would provide an intense contrast in texture and color both. 

 

Fan-spray conifers, such as Arborvitae, Chamaecyparis, Cupressocyparis, Libocedrus, are a way to bring evergreen texture and coloring closer, because they appreciate moister soils than do yews.  All have forms with colorful yellow-friendly foliage, whether darker green, yellow-green, or bright yellow.  Their overall habits are impressively diverse, with forms in many degrees of dwarfness, narrowness, or moundiness.  Be sure to locate them all on the sunny side of 'Richardii'.  

 

Moisture-tolerant plant partners that bring in burgundy include any number of dark-foliaged forms of Acer palmatum, as long as the Acer also enjoy reasonable drainage.  Purple smoke-bushes would only be suitable if they and the 'Richardii' are growing in soils with only normal moisture; 'Richardii' won't tolerate dry soils, while Cotinus coggygria won't tolerate wet. 

 

If you're growing 'Richardii' as a coppice, you could pair it with a clematis with blue or burgundy (or even dark red) flowers and, preferably, yellow or creme pistils that will acknowledge the overwhelming yellow of the poplar.  Clematis are, typically, very welcoming of moist soil, even at the expense of good drainage.  And like Populus alba, they abhor drought.  Consider forms that need annual pruning similar to the coppicing you'd provide for your 'Richardii'.  Clematis can be pruned in Fall or in Spring, so prune in Fall, the preferred season for pruning poplars.  'Niobe' and  'Gypsy Queen' are potential larger-flowered cultivars; C. viticella 'Mme Julia Correvon' and 'Etoile Violette' have especially bright stamens backed by dark petals. 

 

Another clematis possibility would be to combine more on the basis of foliage then flowers, by partnering 'Richardii' with Clematis fargesii or, in Zone 7 and warmer, Clematis armandii.  Both of these clematis have small white flowers that, while attractive, are secondary to the contrast of their darker green foliage with the bright leaves of 'Richardii'.  Both normally grow too large for any poplar host smaller than a free-range tree.

 

Some partner plants have a powerful display of pure-white flowers that can harmonize with the pure-white indumentum of 'Richardii'.  Why not underplant a 'Richardii' pollard with 'Delaware Valley' azaleas?  The flowers are so profuse that the bushes are solid white when in Spring bloom; pollard 'Richardii' only every other year, so that in the alternate years the tree has plenty of colorful foliage and white stems in Spring.  Or grow a low multi-trunked pollard up through a group of 'Delaware Valley'.  Then you can pollard every year.  The new growth might just be starting when the azaleas are in flower, but if you keep the pollarding height to near the top of the azaleas, the azalea flowers and the emerging pollard foliage will be near one another.

Where to use it in your garden

With such vivid and enduring coloring Spring through Fall, Populus alba 'Richardii' is a riveting warm-weather focal point.  Poplars are famously susceptible to a vast array of ailments, though, so don't plant this tree at all if poplars don't thrive where you're gardening.  Even if not, don't plant this tree as your garden's ultimate focal point; who knows when one of the poplar diseases may arise.  Instead, plant 'Richardii' as a secondary focus, so you can enjoy it as long as it lasts.   

 

'Richardii' stems are also great to cut.  It's worth it to grow a tree as a coppice (see "How to handle it" below) just for the resultant steady supply of well-foliaged and wand-like growth. 

Culture

Populus alba 'Richardii' prefers full sun, in almost any soil that doesn't subject the tree to drought.  Spots of low elevation, or alongside fresh water where seasonal flooding is the norm, are both fine.

How to handle it

Plant in Spring or Fall, providing enough water so that the tree isn't drought-stressed as it establishes.  If free-range growth is the goal, formative pruning isn't needed.  See below to grow 'Richardii' as a coppice or pollard.  

How to handle it: Another option—or three!

Populus alba 'Richardii' is colorful when growing free-range, but is even more garden-worthy when pruned severely each year.  The resultant growth can be three to six feet long, with foliage somewhat larger than usual, too.  Populus is unusual in its preferred seasonal timing for such pruning.  Most trees and shrubs that are comfortable with severe annual pruning—Alnus, Catalpa, Gleditsia, Hydrangea, Liquidambar, Liriodendron, Morus, Paulownia, Platanus, Salix, and Tilia—are usually pruned in Winter or early Spring.  For most forms of Buddleja and Robinia, severe pruning is best delayed until mid-spring.  Cut stems of Populus can exude a surprising amount of sap when the tree is pruned in either Winter or Spring; instead, prune in Fall to give cut surfaces time to callous.  I wait until just after the colorful leaves have fallen. Think of your 'Richardii' pruning as the cool-season warm-up for all the other coppicing and pollarding to come.

 

'Richardii' can be grown either as a coppice or a pollard.  Each Fall, cut all branches down to a foot or less to keep 'Richardii' as a coppice.  To grow as a single-head pollard, cut all stems back to stubs at the top of a short trunk.  To grow as a multi-head pollard, cut all stems back to two or three feet.  Unless you have a tall stepladder, cut the the top of the young tree back to eight feet to start training it as a single-head pollard.  Remove lower branches over the next couple of years, as pollarding-induced growth forms a reasonable head.  In contrast, when some forms of willow are pollarded, they can produce new growth eight feet long and longer, and the lower stems could come close to touching the ground by September if the main trunk were only eight feet tall.  They are best pollarded at twelve to sixteen feet high, even though that usually necessitates purchase of an extra-high stepladder.  New growth of 'Richardii' isn't so long, nor are the lowest new stems downward leaning, so a trunk taller than eight feet isn't needed.

Coppicing encourages emergence of root sprouts, as does, to a lesser degree, pollarding.  This makes sense, in that removal of top growth also removes the hormone all such growth produces; that hormone inhibits, at least to a degree, growth that arises from farther down.  Given that the tip of each branch produces such hormone, potential root sprouts would, conceivably, experience some degree of inhibition from each branch of the tree.  Coppicing and pollarding temporarily remove all of those branches—and, therefore, all of that inhibition.  No wonder the root sprouts of a tree that's prone to them in the first place would spring into action afterwards.

 

Prune off root sprouts whenever you have the yen.  Or dig them up, with some roots attached, to share this incredible tree with friends.  Or consider establishing Populus alba 'Richardii' where root sprouts would be desirable:  As the poor man's way of establishing an entire grove without having to plant a grove's worth of individual trees.  Plant one tree and, a few years later, coppice it.  Its roots will sprout your grove for you.  If drainage isn't too poor, underplant with a low spreading evergreen, such as Cephalotaxus harringtonia 'Prostrata', so the grove arises from a mass of gently undulating deep green foliage.  This option could create a unique as well as large garden feature: Poplar roots can spread outward many yards, sprouting along the way.  The roots are so adept at penetrating the slightest crack or opening that controlling their spread by a barrier is almost certainly doomed to failure.  Instead, establish the grove within a large lawn, so that out-of-bounds root sprouts can be routinely cut down as the grass is mowed. 

 

On the basis of the potential size of such a grove, establishing one isn't advisable if poplars contract any of their many diseases where you're gardening; see "Downsides," below.  But after nearly ten years, my 'Richardii' remain trouble-free; could I possibly create room for such a grove in my relatively compact property of an acre and a half?

 

One last appeal on behalf of any grove formed by root sprouts:  The entire grove is called "clonal" because it has arisen (literally, in the case of such a strongly vertical tree like a poplar) from a single individual, without benefit of propagation by seed.  A clonal grove is one individual tree, albeit one with many trunks.  Sassafras (Sassafras albidum) is another tree that readily "groves itself."  The champ, however, is another species of poplar.  Quaking aspen, Populus tremuloides, can form clonal groves covering many acres.  The largest of them, named Pando, covers over one hundred acres, and has been growing for about 800 centuries.  (Yes, 80,000 years!)  It currently has about 47,000 stems, and is thought to be one of world's largest creatures.  When you establish any clonal grove, you are welcoming into your garden a living entity of, potentially, exceptional size and age.

Downsides

The straight species, Populus alba, is notoriously problematic.  The far-reaching roots can invade any plumbing line within sixty feet.  The roots send up sprouts that, if not controlled, will result in a widespread clonal colony.  The trees are prone to an enormous list of diseases that can render them unattractive, and often kill them outright.

 

And yet for me, Populus alba 'Richardii' has been slow growing in youth to the point of reticence in the ten years since planting, and has never contracted any insect, bacterial, or fungal ailment.  The foliage is stunning Spring through Fall, and the tree's response to pollarding and coppicing is the model of restrained enthusiasm.  It's possible that the trees are protected from contracting many of the usual poplar ailments because, to my knowledge, there aren't any species of Populus for miles around.  The largest regional wholesaler lists no Populus at all; none of the specialty nurseries I shop at locally carry any either. 

Variants

I'm not aware of other forms of Populus alba that have the potential to perform well.

Availability

On line.

Propagation

By cuttings and by separating the root sprouts from the parent tree.

Native habitat

Populus alba is widely native to southern and northern Europe, from Spain to Germany, into central Asia.

 
 
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