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Plant Profiles

Hardy Orange: Fall Foliage



I've had my hardy orange in training as a topiary for over twenty years.  As usual, it has grown lustily over the Summer, and so it's time for a trim.  Between May and early November, new growth can grow from a foot to six feet long.  Because the hardy orange won't do any more growing until Spring now that the weather's turning chilly, if I clean the topiary up now it will hold that shape all Winter long.


Could any plant have a more joyful Fall color?  And now that the leaves have turned forsythia yellow, the huge green thorns are suddenly much more visible. 




Hardy orange bears fruit—real oranges, albeit only as big as ping-pong balls—but the chrome yellow foliage outshines it.   In another week or so, the foliage will drop and leave the oranges—which are, in fact, orange—in full view. 


Can you spot any oranges hiding amid the foliage?




An hour later, both balls are largely cleaned up.  But there's more to be done: A little more off the top ball, please, and some better contouring on the bottom ball, whose top is too flat.




OK, OK, I'll get back up the ladder.  Stay tuned for pictures when the leaves are down and the oranges are in full reveal.



Here's how to grow your own topiary of hardy orange:

Latin Name

Poncirus trifoliata

Common Name

Hardy orange


Rutaceae, the Citrus family.

What kind of plant is it

Deciduous flowering shrub or small tree whose leaflets are in clusters of three.


Zones 6 - 10


Broadly upright, with one or several trunks.  Densely twiggy growth, green-barked when young, that is studded with fierce green thorns to four (!) inches long.

Rate of Growth


Size in ten years

Twelve feet high, taller in milder climates.


Dense and bulky.

Grown for

its year-round appeal: White flowers (without fragrance, alas) in early Spring; then small green three-part leaves; then colorful (but small and pithy) small orange citrus fruit; then yellow Fall foliage; then, in Winter, the full reveal of the dense twigginess and startlingly large green thorns.

Flowering season

Early Spring, just before the leaves emerge.

Color combinations

The white flowers in Spring go with everything, as do the green leaves of Summer and the (dark) green bark of Winter.  By the time the foliage colors most intensely in Fall, its color—forsythia yellow—isn't the four-letter word it would be if it occured in Spring.  By November, any strong color is welcome.  The same is true for the bright-orange fruit.  Who cares what color any of the neighboring plants are? 

Partner plants

Although Poncirus can be a coloristic partner to just about anything, its remarkable thorns and possibillities for handling (see "How to handle it" below) make careful thought necessary about anything that gets planted near it. 


If the bush is growing free-range, it will form a broad and somewhat pendulous mound.  The thorns would make mowing grass under it dangerous at best.  A better choice would be to plant it in a large expanse of a low groundcover, such as vinca or pachysandra, which will prevent pedestrians as well as the lawn-care folks from wandering into the bush by mistake.  Almost any free-range horticulture higher than a groundcover would get tangled in the bush's low branches, anyway, and if a breeze pushes the growth of a neighboring plant into the poncirus, its thorns will probably take that growth hostage.  So limit nearby plantings to low and prostrate. 


If you're planning on pruning your hardy orange at all—whether just occasionally, to limb it up; or with seasonal rhythm, should you decide to train it into a topiary or an espalier—also try to limit the height of nearby plantings.  But this time, choose groundcovers that are foot-friendly as well as low.  Vinca and pachysandra would again be good choices; low ferns or hostas would not.  You shouldn't have to be looking down and wondering where to put your foot at the same time you're trying to keeping a wary fix on the next fiercely-thorny branch you'd like to prune back.

Where to use it in your garden

Because Poncirus is so thorny that you should keep anything nearby out of "piercing range," it's not the plant to use as part of a more general sweep of shrubbery.  Because Poncirus will always need to be kept separate from its neighbors, this inevitably means that it gets extra focus.  Why not make not just a virtue of necessity, but a triumph of it, by planting your Poncirus where there's no doubt at all that it is, indeed, the star of that part of your garden?  Site it in the middle of an expanse of low groundcover that's generously wider than the bush would ever grow, too.  In such a prominent and "well skirted" setting, your Poncirus will be all the more likely to get the respect—as well as the respectful distance—that is the safest.     


All possible heat and sun.  Any reasonable soil.

How to handle it: The Basics

Poncirus is tough and tolerant so, as long as you're not gardening in true xeric conditions—Tucson, say—you don't need to amend the soil or provide supplemental water for the bush itself.  But, depending on the groundcover you partner it with, you may need to amend the soil and water during drought for that.  Either way, the Poncirus will be happy.


If you're gardening at the colder end of Zone 6, your Poncirus may get some tip damage over the Winter.  Clip this off as early as you want to work in your garden in the Spring: the dead tips won't have the dark green bark of the live ones, so are easy to spot.  Poncirus branches out vigorously after pruning, so the bush will normally bounce back stronger than ever if Winter damage is only modest.

How to handle it: Another option—or two?

Poncirus is naturally twiggy, and because the stems have such plentiful and spike-like thorns, too, the growth tends to knit together spontaneously into an impenetrable and stiff mass.  This is great if you'd like your Poncirus to be a security barrier.  But it's a challenge if you need to lop off more than surface twigs; you'll usually need to grasp a cut branch with your clippers to have any hope of extracting it from the surrounding tangle of thorny growth.  And of course, those same thorns can make it tricky even to get your clippers close enough to the cut end to grab ahold of it strongly enough for a successful "extraction."  If there were long-handled "poncirus tongs," I'd get a pair.


Despite the challenges of pruning, Poncirus branches so quickly, even after radical pruning, and often puts out lengthy and very flexible wands of new growth that can be many feet long, that its potential for topiary or even espaliering is substantial.  For topiary, let the bush grow free-range for a few years, then select the main branch that's the straightest to become a trunk, cut off all the other branches around it, and (now that you can reach it without becoming speared by the thorns of adjacent branches) tie it to a thick stake so it can grow in a true vertical.  Let it get to the height you want—four feet is fine, six feet would be fabulous—and then, in Spring, cut off the top tip.  Let the rest of the bush grow free-range that year.  But the next Spring, prune off all side branches, current or new, that are arising anywhere from the ground to three feet up the trunk.  And continue to tip the top growth of the bush, even as you let most of the growth remain, to bulk up and form the head of the topiary. 


With just a season or two of this pruning, your Poncirus will be very helpful in forming much of a round head by itself.  The bush is particularly considerate in producing branches at the underside of the head, which can be a challenge to encourage with other topiary subjects.  For some years, you need only clip the bush in Spring—try to wait until after it flowers—as the head of the topiary densifies and enlarges. 


Eventually, though, you'll realize that the head is (at last!) getting too large—mine was five feet across (and five feet higher than the four-foot height where I'd first pinched the growth) before this had occurred to me.  Merely cutting into year-old growth will no longer suffice to control the topiary.  You'll need to cut into even older growth, which means thicker branches that are, each in its own devilish way, quite enmeshed into all of its neighbors.  Working slowing and patiently—and ruthlessly—saw, chop, and lop off a substantial amount of the topiary's head as early in Spring as you can stand to work.  Don't wait until the flowering's done: Your bush will need all possible warm weather to recover from the pruning it's receiving.  Plan on reducing the diameter of the head at least by half.  Yes, when you're through, the bush will look like a plucked chicken.  Don't lose your nerve or your energy.  Do it!


By Summer, the bush will have sprouted into lush growth as never before, and by Fall you'll wonder what all the fuss was about.  Now that your topiary is this old, you can also tip-back this new growth that Fall—just as I'm doing with my old topiary, after the Fall foliage has arrived—not just in the following Spring.  Poncirus becomes hardier as it grows larger and older; any bush old enough for radical pruning is hardy enough to tolerate pruning in the Fall, too, not just in the Spring.

Quirks or special cases

If even Poncirus topiary isn't too forbidding, you could consider creating a Poncirus espalier.  Plant the bush by a wall or a fence or a galvanized frame—anything to which you can tie branches wherever you need—where it will get full sun. 


As with establishing a Poncirus topiary, let the bush grow free-range two or three years.  But early the next Spring, tie any of the major branches to your support that can be muscled into relative alignment.  Cut off any that are too much work.  Prune off any side branches that aren't already in the general plane of the espalier; Poncirus branches so readily there's no worry that you won't have others to choose from soon.


The bush will also put out occasional "long wand" shoots directly from the trunk.  These are an espalierist's dream, because they're flexible and have almost no side branches.  (They do have their full complement of thorns, though.)  Perhaps the ultimate poncirus espalier would be started by cutting your two-or-three-year-old bush down to six inches in early Spring instead of tying its established branches to the frame.  This will produce a raft of long-wand shoots over the Summer, which by Fall you can then (gently) fan out against your espalier frame. 


Because Poncirus blooms early in the season, try to resist pruning established topiary and espaliers until after the blooms have past.  The flowers are delicate and profuse—but brief—so you just need to leave your pruners in the holster for an extra week. 


The thorns are as dangerous as those of any cactus.  Wear protective glasses and thick-soled shoes when working on this plant.  When pruning, take care to put each clipping directly into the wheelbarrow or basket; stray clippings would be painful to "discover" when kneeling or weeding later in the season.  In my experience, Poncirus self-seeds only modestly, so you'll need to pull only a few seedlings each season.  They don't get thorns until they're several inches high, so yank when they're young!


'Flying Dragon' has contorted stems and even contorted thorns.  It's not substantially more interesting than the species itself, but is often more available.


Because Poncirus is difficult and even dangerous to handle, it's generally available only at specialty nurseries or on-line.


Seeds or cuttings

Native habitat


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