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Plant Profiles

Round-leaved box

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Leaves almost an inch long!  If you're a box, that's huge.  'Rotundifolia' is the cultivar to grow for a contrast from the dense and (comparatively) small-leaved look more typical of the shrubs.  It's truly boxwood writ large.

 

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The habit of 'Rotundifolia' is unusually loose, as well.  See "How to Handle it" and "Quirks" for options that make the most of it. 

 

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I have five young 'Rotundifolia' shrubs in one of my nursery beds, and I'lll transplant them all to their permanent site this Spring.  Although that location is outside the portion of the garden that's protected by deer-fence, and even though the foliage of 'Rotundifolia' is the largest and therefore the juiciest of all box species and cultivars, the shrubs will never be nipped, let alone munched.  Thanks to boxwood's typical whiff of cat-pee when the foliage is brushed, deer leave the plants strictly alone, thinking they've been marked by a fierce feline predator.  

 

 

Here's how to grow this luscious shrub:


Latin Name

Buxus sempervirens 'Rotundifolia'

Common Name

Round-leaved boxwood

Family

Buxaceae, the Boxwood family. 

What kind of plant is it?

Broadleaf evergreen shrub.

Hardiness

Zones 6 - 9.

Habit

Mounding, dense, full to the ground, taller than wide.  The shrub is rotund in overall shape as well as in leaf shape.

Rate of Growth

Medium. 

Size in ten years

Four feet tall and three feet wide.  In twenty years, potentially, to ten feet tall and nine feet wide.

Texture

Fine-grained but casual.

Grown for

its habit:  'Rotundifolia' has a looser habit than is usual for box, and it's worth celebrating it by letting the shrub grow free-range.

 

its foliage: The leaves of 'Rotundifolia' are noticeably larger than those of the straight species, and are dramatically larger than those of dwarf box cultivars such as 'Morris Midget' and 'Suffruticosa'.  True to the name, the leaves are rounded, not pointed.

 

its tolerance of pruning:  Like all box, 'Rotundifolia' can be shaped regularly; if needed, it can be even be "pruned" with a chainsaw.

 

its imperviousness to deer, who avoid all boxwood.  The shrubs have a characteristic odor, faint but accurate, of feline urine, which deer interpret as the sign of a carnivore.  Lucky us! 

Flowering season

Spring; box flowers are small and white, and are not showy.  Bees are very glad of them regardless.

Color combinations

'Rotundifolia' goes with everything.

Partner Plants


The foliage of 'Rotundifolia' is large only in comparison to that of other forms of Buxus.  Amid the larger world of "extra-buxial" foliar possibilities, it's small, indeed.  Why not have 'Rotundifolia' play the ironic role of the small-foliaged contrast by pairing it with truly huge leaves?  Should you ever be confronted with a Magnolia megaphylla that needs a lot of something evergreen massed near or even under it— well, now you're prepared with a solution.  Nothing like leaves that are three feet long to make those that are barely an inch look microscopic.  

 

Looking through the other end of the telescope, pair 'Rotundifolia' with ferns that are especially ferny.   Pass right by the large-lobed fronds of royal ferns and Christmas ferns.  Instead, what about a specimen of 'Rotundifolia' arising from a sweep of hayfern, Dennstaedtia punctilobula?

 

The loose habit of free-range 'Rotundifolia' would be heaven, both visually and structurally, for a partner plant that needs to climb or scramble through a host.  Choose plants that either don't get too large, or are at least easy to keep in proportion.  Spring-blooming clematis, such as the alpina or macropetala species and cultivars, would be ideal—as would be one of the cultivars that gets cut to the bottom bud each Spring in one fell swoop.  You sever all the stems, then extract all of last season's top growth from your 'Rotundifolia' in one gloriously messy hank.  Choose from the less-rambunctious cultivars of C. integrifolia or C. viticella; cultivars of C. orientalis will grow too large, at least if they're happy.      

Where to use it in your garden

'Rotundifolia' has many uses.  If you can give it the room it needs to grow free-range, it's a graceful (if bulky) screen.  It can also be massed as a very large-scale groundcover in the high shade of deciduous trees, such as oaks, or near the low canopies of trees with ferny foliage, such as metasequoias and taxodiums. 

 

If you're confident of your long-term commitment to pruning, 'Rotundifolia' can be repeated down a long border, one egg-shaped shrub every, say, twenty feet. 

 

If you're blessed with a mature 'Rotundifolia', you might respectfully explore how some discreet thinning and limbing-up could help your specimen display a graceful limb, a hint of delicate ankle, or even a shockingly daring cleft of decolletage—thereby transforming a shrub that is merely large into one that is also dramatic and even audacious. 

Culture

Full sun or part shade, in almost any soil with good drainage.  Box is flexible about pH, thriving in soils that are moderately acid, neutral, or fairly sweet. 

How to handle it:  The Basics

Box is unusually easy to establish.  Colder than Zone 7, plant in Spring only.  Be sure to provide enough water to establish the shrub the first season; after that box is drought tolerant.  Growth is lusher with adequate moisture. 

 

In Zone 6, new plants welcome Winter protection for a year or two.  Spray with antidessicant in late Fall; you might even cover with wind-baffle fabric by January.  By their third WInter, starter plants will be fully hardy. 

How to handle it: Another option—or two?


'Rotundifolia' will eventually become much larger than when you planted it, but because it will take many years to do so, it's not likely that you'll have been uncompromising enough, both at planting and every year along the way, to give the shrub all possible room, forever.  Thus, some pruning will usually be needed.  

 

Box is legendarily responsive to it, and will resprout promptly even from stumps.  Do any substantial pruning in the Spring, so the shrub can produce new foliage that same season to hide the bare inner reaches of branches that the pruning might reveal.  If you do such pruning in the Fall, you'll be looking at those bare parts all Winter long.  Pruning that is only within the shrub's outer foliage can be done in Spring or Fall as long as the Fall pruning is delayed until the weather is reliably cool or even a bit cold.  New foliage won't be produced until the following Spring, and so avoids any danger of being Winter-killed.  Plus, the shrub holds its just-pruned sharpness all Winter long.

 

To retain the loose habit that is so characteristic of 'Rotundifolia', control size by reaching into the interior of the shrub, a couple of feet back from the tip of each branch that is too long, and then cut it off.  The overall size of the shrub will be reduced, but its casually open and "ventilated" look will remain. 

Quirks or special cases

'Rotundifolia' can also be pruned with architectural authority, into hedges and topiary with a supremely fine-grained and smooth surface.  Pruning to such close tolerance is trickier with shrubs with such comparatively large foliage.  If you use mechanized pruners, individual leaves will be partially removed as often as stems and branches, and the healed edges of the stubs of those leaves is noticeable.  You avoid all of those leaf scars if you use hand pruners, but then you'll need to cut each stem tip individually, which greatly lengthens the time needed to do the job.  Be sparing in your use of 'Rotundifolia' for intricate pruning, choosing smaller-foliaged subjects for large-scale situations that also call for pruning.  Yew is always the best first choice, but box cultivars with the more typical smaller leaves are also effective.

Downsides

Box is susceptible to a variety of insect pests, but plants that are sited well are more resistant.  Check with your state's USDA Cooperative Extension Service to see if there are challenges for box where you're gardening.

Variants

Ah, the diverse world of box.  Although there are just two main species—Buxus microphylla and B. sempervirens—there are hundreds of cultivars, with habits from "micro-mini," such as 'Morris Midget', to many gradation of merely dwarf, to broad and upright (again, at many gradations), to upright or even narrow.  With the exception of 'Rotundifolia', foliage is always about the same length, but can vary from narrow and pointed to nearly round.  Some cultivars have leaves edged in cream; some others have new foliage that's yellow. 

 

In addition to 'Rotundifolia', my favorites include 'Morris Midget'; 'Tide Hill', with tiny leaves, a very short height (below two feet), and an unusually broad spread (to five feet or more); 'Vardar Valley', broad but usually not higher than two or three feet; 'Elegantissima', with cream-edged leaves; 'Wanford Page', with yellow new growth; and 'Graham Blandy', extremely tall and narrow.  All of these are cultivars of just one or the other of the two box species, B. microphylla or B. sempervirens.

 

There are also cross-species hybrids—the Sheridan hybrids, developed at Sheridan Nursery, in Ontario—that combine the greater hardiness of B. microphylla with the greener Winter foliage of B. sempervirens.  They are all dense and mid-height mounders, and thrive in cold as well as hot climates.  From the names of the cultivars to date—'Green Mountain', 'Green Mound', 'Green Gem', 'Green Ice', and 'Green Velvet', and 'Chicagoland Green'—you can tell how notable their improved Winter color is.

Availability

On-line and, occasionally, at retailers.

Propagation

All boxwood species and cultivars propagate easily by cuttings.

Native habitat

Buxus sempervirens is native to western and southern Europe, as well as north Africa, from Great Britain to Turkey.

 
 
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