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Plant Profiles

Empress Tree in Winter

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A Paulownia pollard in Winter: Without their huge leaves, the eight-foot "twigs" it grew all Summer look like huge claws.  The pollard could be a memorial to pterodactyls.

 

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Late Winter and early Spring is the season for the tree's annual massacre.  I saw each limb back to just above its lowest pair of leaf buds.

 

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Although the leaves themselves are huge—well over a foot across—the buds they arise from are hard to spot.  In the picture above, the new leaf on this side of the branch will emerge from the pimple-sized bump right above the horizontal lima-bean that's the scar of last year's leaf.

 

Shorn of its eight-foot limbs, the Paulownia is a starkly-bare trunk.

 

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In late  May, massive foliage will erupt as the new twigs shoot forth from all of the stubs.  By September, the pollard will be larger than ever—and after the leaves fall in late October, a pteradactyl memorial once again.

 

 

Here's how to grow this unique tree:

 

Latin Name

Paulownia tomentosa

Common Name

Empress tree

Family

Scrophulariaceae, the Figwort family. 

What kind of plant is it?

Deciduous tree.

Hardiness

Zones 5 or 6 to 9 east of the Rockies. In coastal California, Paulownia succeeds even in Zone 10, where frost is both mild and very rare.

Habit

Zones 6 to 9: Upright with a broad canopy, looking much like a catalpa. 

Single-trunked unless coppiced, or growing where wildfires occur, in which case the tree happily resprouts from the stump, as well as directly from its roots, to form a multi-trunked grove.

 

In Zone 5, a die-back shrub that resprouts from the stump or directly from the roots. 

Rate of Growth

Extremely fast, especially where Summers are hot. 

Size in ten years

Thirty feet or taller; twenty to thirty feet wide.  Potentially to sixty feet tall and forty feet wide, although it's more usual that even older trees are less.  Shorter still when grown as a coppice, pollard, or die-back; see "How to handle it" as well as "Quirks and special cases" below.

Texture

In leaf, full.  Out of leaf, coarse; coppiced or pollarded specimens are so coarse that their gaunt and even prehistoric character becomes a defiant attribute.

Grown for

its foliage: The velvety rounded leaves come to a point, like the leaves of sunflowers.  At five to ten inches long, they're as large as those of sunflowers, too.  Trees that are coppiced or pollarded develop leaves three or four times as large, to two feet long for just the leaf blade itself.  Add another foot or so for the leaf stem—the petiole—and you have leaves that are a yard long.  They are, unapologetically, a horto-stunt.  Neighbors will wonder how you've managed to grow the most enormous sunflower ever.

 

its flowers:  Unique in trees that are hardy as cold as Zone 6, Paulownia flowers are lavender-blue, in foot-tall pyramidal panicles held above the branches just like the flower clusters of chestnuts.  Individual flowers can be two inches across at the lip, and two inches deep.  They emerge in mid-Spring, before the leaves do, for a show that's the equal of any flowering tree in the neighborhood.  See "How to handle it: Another option—or two!" and "Quirks and special cases" below for strategies on how to either encourage or prevent flowering.

 

its flower buds: The orange-buff buds are held on the panicles through the Winter, and are a show in themselves.  I always appreciate seeing the erect trusses of Paulownia buds on otherwise leafless trees in the Winter landscape in California, where any deciduous species is a treat amid the omnipresent green of broadleaves, palms, and succulents.       

 

its lumber:  The trees are quick-growing, in part because they're able to solidify new growth so quickly with white pith, which results in lumber of unusual smoothness and pale color.  Paulownia wood is favored for detailed carpentry such as jewel boxes and chests replete with drawers, paired doors, and sliding tops.

 

its unusual response to severe pruning:  Trees that are sawn back to a stump or even to the ground resprout with almost alarming enthusiasm.  As long as Summers are mildly hot—New England is warm enough—the sprouts can soar to fifteen or even twenty feet by September.  See "How to handle it: Another option—or two!" for tactics to maximize this already-rampant growth.

Flowering season

Mid-Spring, before the leaves emerge.  Mid-May in Rhode Island.

Color combinations

The color of the leaves, bark, seedpods, or buds of Paulownia is not distinctive enough to warrant collaborators whose talents are primarily coloristic—but the possibilities of the startling lavender flowers more than makes up for that.  They arrive as the wave of Spring flowers is cresting, so there are many ways to bring the ready choices of yellow, pink, deep purple, indigo, white, and burgundy into the picture.  Orange would be a brilliant choice, in all senses of the word.  Paulownia flowers are unusually cosmopolitan in their partnerings; only red would be utterly foreign.    

Partner plants

Paulownia trees grow so fast that they are as big as full-sized magnolias before they're mature enough to flower.  Plants whose flowers or foliage are colorful enough to riff with those of the Paulownia need either to be born on trees so they're high enough to be seen in the same glance, or on shrubs that are planted in large enough groups to function as an enormous groundcover.

 

Paulownia foliage is somewhat late to emerge, but the leaves of companion trees with colorful leaves may already be in place.  Could a Paulownia be planted so as to have a purple-leaved beech in view behind it?  This early in the season, the beech leaves are at their absolute darkest.  Given the vastly slower rate of growth of a beech tree, the Paulownia would almost certainly to have been planted years or even decades later.  The pairing could only be an accident: No one is likely to be able to put a codicil in their will stipulating that, after the just-planted purple beech has grown for fifty years, it's finally time to plant the Paulownia nearby.   

 

Although nothing but bamboo is every bit as speedy as a Paulownia, Spring-blooming trees are much faster growing than beeches, so could be thought-through as well as planted at the same time as the Paulownia.  But Spring flowers don't last long; a gap of even a week between the peak of bloom of the Paulownia and that of its intended color-contrast partner could make their proximity useless.  Would any yellow-flowering magnolia be in bloom the same time as the Paulownia ?  Visit an arboretum that has a lot of magnolia cultivars—and would any of them not?—and track how well their different weeks of flowering overlap with that of a local Paulownia.  There are hundreds of magnolia cultivars, and the blooms of later-flowering varieties might emerge six weeks or more after the earlier.  Surely, some are at their best when the Paulownia flowers are, too.

 

The same caution about synchronized blooming applies to flowering fruit trees as well as rhododendrons and azaleas.  Would it be possible to have a Paulownia in bloom at the same time as its underplanting of, say, fifty vermillion-flowered Exbury azaleas?  Only by comparing plants in gardens near yours could you become confident enough to risk such a commitment.  

 

It's less suspenseful to bring some color and contrast to a Paulownia that's not in bloom.  The leaves are out from late May to hard frost, and the naked branches and trunks are in full view from hard frost to late May.  The bare tree in Winter is easy:  Plant ivy or climbing euonymus.  Either would look especially snappy clothing the short trunk of a pollarded Paulownia; see "How to handle it" below for how to train one.  Free-range Paulownia trees tend to look a bit messy in the Winter, so you'd want to think twice about adding the additional off-season tangle of one of the tree-climbing roses—such as 'Kiftsgate', 'Sander's White', 'Rambling Rector', 'La Mortola', 'Mermaid', or Rosa banksii—as voluptous as their warm-weather show would be.  (For myself, though, I'd forgive months of Winter mess for an incredible warm-weather display, and the indelible memories and pictures it would inspire.) 

 

Perhaps the best options are among the largest cultivars and species of Clematis.  If you're lucky enough to be gardening in Zone 7 or warmer, C. armandi would be hardy.  Its rambunctious vigor and large, evergreen, narrow-lobed leaves would be interesting year-round, when the Paulownia is in leaf and when it's just "in branch."  There's also the chance that the vine's Spring flowers would coincide with the tree's.  Clematis fargesii is even easier.  It has no qualms about climbing twenty feet and more, and provides scatterings of white flowers much of the Summer.  You can let it grow as a permanent and woody explorer through the canopy of the Paulownia

 

If you're growing your Paulownia as a pollard, its canopy would be low enough that you could lead one of the larger Group C Clematis up into it; some of them plan on growing fifteen and twenty feet even though they were cut back to lowest buds in April.  Choose one of the cultivars of Clematis orientalis, say, or Clematis rehderiana.  Plant one six or eight feet away from the Paulownia so there's minimal competition from its roots.  Provide an extravagantly nutritious bed for the clematis:  You want the vine to put out all possible growth, and of maximum length. 

 

Because the Paulownia looses its entire canopy in its Spring pollarding, give the Clematis a permanent stake (I recommend rebar) up to eight or ten feet tall.  About the time the Clematis has grown up to the top of the rebar, the new growth of the Paulownia will have extended outward far enough to meet it.  Cut the Clematis back to its lowest buds the same time you saw the limbs of the Paulownia pollard back to theirs. 

Where to use it in your garden

A free-range Paulownia is not a tree for small gardens.  When it isn't dropping the flowers (lovely as they are when littering the ground), it's dropping seed pods, huge brown  leaves in Fall, and miscellaneous twigs.  A Paulownia as the courtyard tree to a city garden would be a nightmare.

 

Instead, plant a tree that you intend to grow to full size far away from pavement, let alone parked cars.  Fortunately, the trees are so showy in bloom that they have enough gravitational pull to be seductive even at a distance.  You can't resist walking over to see what could possibly be so showy.

 

A coppiced or pollarded Paulownia, by contrast, is at home in gardens small or large.  Yes, there's the Fall foliage to sweep up, but unless you're growing your pollard so that it flowers—see "Quirks and special cases"—there are no flowers or seedpods to get underfoot, or to mess up the roof of a car.  The foliage of a coppice that's allowed to grow only single-trunked is so enormous that you'd best allow visitors access right up to the leaves.  That the huge leaves are bizarrely impervious to wind damage only increases everyone's need to finger them.   

 

Paulownia pollards and coppices are so striking year-round that they are just as effective as a full-grown Paulownia for planting at a distance.  The claw-like limbs of the pollards are sculptural, in a Louise Bourgeois way, and would be enhanced by being back with tall evergreens.  (Then again, what isn't enhanced by being backed with tall evergreens?)  If I were gussying up a huge landscape—a modernistic corporate campus or museum, say—I would plump for planting a line of Paulownia pollards, with trunks clothed in ivy, backed by a twenty-foot-tall hedge of giant arborvitae, and underplanted with something low, deciduous, and shade-loving: Yellow-root, Xanthorhiza simplicissima.

Culture

Full sun only, in any reasonable soil and even those that aren't.  Paulownia will not tolerate shade.  Fastest growth in hot climates, and in sites with rich soil with ready moisture.  I have never seen a Paulownia whose foliage had scorched from drought, but with such enormous foliage, it wouldn't be pretty.  Given the leaves' size, the trees are startlingly tolerant of exposed and seashore locations as long as they're growing in "real" soil, not sand.  I still recall Paulownia trees growing only feet from open water on the Connecticut shore; they were monsters all.

How to handle it: The Basics

Plant in Spring, in absolutely full sun.  Trees grow so fast there is no point in planting anything other than a sapling, or even a seedling.  Provide sufficient water to get the tree established, and then ignore it.   

How to handle it: Another option—or two?

If you'd like to grow leaves with the largest surface area of any hardy tree, get out your folding saw early in the Spring of your young Paulownia tree's third year of residence in your garden.  And then saw it down to a stump.  Even by the third year, the tree may be so tall that it might be prudent to cut it down by sections; your last cut should be a foot above ground.  Velvety-leaved new shoots will spring from the trunk and even from some of the roots. 

 

After they are six or eight inches tall, knock off all but the strongest of those shoots; they are fragile, so this takes only seconds.  The remaining sprout will grow a foot or more per week, and be studded with pairs of giant leaves as it grows.  Each pair is at ninety degrees to the one beneath it.  If you're gardening in a cool-Summer climate whose Winters are, nonetheless, still mild enough that Paulownia is hardy—think Ireland or Scotland—the sprout might, as one British book exclaimed, "soar" to six or eight feet.  In a typical sweltering Summer in the United States, expect a more literal enactment of "soar," to fifteen or even twenty feet.  

 

If you choose to let several sprouts thrive instead of just one, their foliage is still larger than usual but not nearly the parasols that are born by single-sprout growth.  None of the shoots will become quite as tall, either, but the overall bulk of the resultant shrub is much fuller.  By September, expect a massive leafiness ten to fifteen feet tall and eight to twelve feet wide. 

 

If your climate is severe enough—the cold end of Zone 6 down into Zone 5—your Paulownia may die back to lowest buds most Winters.  This isn't a savings in labor: You still need to saw the dead stems down in the Spring.  If only the tree would then saw off its own dead stems, so it would be self-coppicing. 

 

Paulownia trees also grow lustily as pollards, which is how I'm growing mine.  As with training a Paulownia as a coppice, start in the third Spring, and saw all branches off an inch or two from the trunk, just above their lowest pair of leaf-buds.  Saw off the trunk itself, too, at about six feet tall, higher if you're comfortable working from a step-ladder.  The new shoots will grow six to ten feet over the Summer.  Every year thereafter, saw those shoots off at their lowest pair of leafbuds early the following Spring.

 

Paulownia pollards are an unusual and also extremely effective solution for quick as well as storm-proof Summer privacy, where waiting for a "normal" tree or hedge to grow to fifteen or twenty feet would be a matter of a decade or two, and where pruning at that height would be awkward at best, dangerous at worst.  Plant individuals six or eight feet apart. 

Quirks or special cases

With a different timing of your pruning, you could grow Paulownia as a pollard that also flowers.  Then you can enjoy the species' unique blossoms while still keeping the tree to a fraction the size of a free-range specimen.  Pollard initially, as above, but then let the shoots grow all that Summer and then through the following Summer—or two!—as well.  

 

Each year, check out the tips of the newest growth in late Summer and Fall: If growth is old enough for bud formation, the characteristic vertical panicles of tan spherical buds will be readily visible, especially after frost has caused leaf shed.

 

My tree was last pollarded in 2012, and started forming buds in late Summer of 2014—the third Summer since pollarding. (If your growing season is long and hot, buds might form even at the end of the second Summer after pollarding.) These buds will develop into flowers in Spring 2015; after they're through, I'll pollard and begin the cycle afresh. Another advantage to pruning right after the bloom season is complete in May: You prevent the tree from setting seed.

Downsides

Paulownia can self-seed with abandon.  While it is intolerant of shade, and therefore cannot infiltrate into established forests, it's not unusual for Paulownia to colonize sunny habitat, such as along railroad tracks.  I was fortunate, once, to take Amtrak from New York City to Washington, DC, during the tree's Spring blooming season, and always think fondly upon the riotous floral display of trackside trees on the approach to the Philadelphia station.  Check with local nurseries as well as your local USDA Cooperative Extension Service Office to see if Paulownia is not recommended in your area.  Even so, you could responsibly grow the tree as a coppice or pollard, which prevents seed-set.

 

Although the trusses of buds for the flowers in the coming Spring are showy in Winter, the seedpods from the flowers of the previous Spring can persist into Winter as well.  Trees that are ungroomed can look messy in the cold months: there's just too much going on up there in the canopy.  All the more reason to grow flowering Paulownia trees only as pollards.  If you prune in early Spring, there are no flowers and therefore no seedpods.  If you prune in late Spring every other year, there are flowers, but still no seedpods. 

Variants

The cream-colored flowers of Paulownia fortunei are even larger, and in larger panicles; those of P. fargesii are near-white, speckled with dark lavender, and are in denser panicles.  P. coreana may be a bit hardier.  There are several other species, too, almost never offered for ornamental gardens.  In truth, until a cultivar appears with notably darker flowers, or foliage that's variegated or solidly-hued in another color than green, P. tomentosa is all you'll ever need to grow.  The ultimate fantasy:  A gold-leaved cultivar with indigo flowers.  What a joyful noise it would make. 

Availability

On-line.

Propagation

By seed.

Native habitat

Paulownia tomentosa is native to China. 

 
 
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