A Gardening Journal

Sky Pencil holly

ilex-crenata-sky-pencil-640

 

"Pencil" evergreens often have trouble keeping themselves together after a heavy snow.  I keep mine rail-thin all Winter despite the weather, with a quick spiral of twine from bottom to top—and then back down to the bottom—each Fall.  What's ten minutes of twine in return for months of storm-proof beauty?

 

'Sky Pencil' holly routinely tops eight feet and sometimes twelve; mine's already eight feet, and I live in hope of its continued upward thrust.  So the up-and-down twine spiral involves a stepladder, too.

 

ilex-crenata-sky-pencil-wrap-640

 

That quick November visit is my last chance to pay respect to an otherwise maintenance-free shrub before Winter descends.  The Fall "twining" is my opportunity to, literally, give this great holly a hug, a thanks for another exciting season as one of the pinnacles of my garden.  

 

 

Here's how to grow this easy and versatile holly:


Latin Name

Ilex crenata 'Sky Pencil'

Common Name

Sky Pencil holly

Family

Aquifoliaceae, the Holly family.

What kind of plant is it?

Broad-leaved evergreen shrub.

Hardiness

Zones 6 - 8; sometimes listed as Zone 5

Habit

Narrow and columnar; full to the ground.  Depending on training, four to  six times as tall as it is wide.

Rate of Growth

Medium.

Size in ten years

Two feet feet across and eight feet tall feet tall.  Potentially to twelve feet tall.

Texture

Dense and rigid, but not with a "tight" surface.  Unlike, say, boxwood, whose foliage crowds the outer extent of growth, creating a uniform "paving" of foliage and leaving a largely leafless and open-branched interior, Ilex crenata always maintains a deeper texture.  Both bushes appear similarly dense at a glance, but the density of box is comparatively superficial.  Ilex crenata is dense through-and-through. 

Grown for

its foliage:  Narrow dark-green leaves crowd the branches, and are reliably evergreen down into Zone 5. 

 

its habit: 'Sky Pencil' is exceptionally narrow in youth; even when growing free-range, it's impressively upright.  All the branches arise from the bottom; there isn't a trunk per se

Flowering season

Spring, but holly flowers are small and not showy.  'Sky Pencil' is a female, so will also bear black berries, but they aren't showy, either.

Color combinations

Ilex crenata 'Sky Pencil' brings only dark green to the garden, so it goes with all other colors. 

Partner plants

If allowed to grow free-range, 'Sky Pencil' has great natural dignity and integrity.  It's naturally full right to the base, so can be sited right at the front of plantings.  It grows tall enough to be showy even at the back of deep borders, where its bottom four to six feet might not be visible from June through frost.

 

Large foliage is always a satisfying counterpart to small.  'Sky Pencil' brings such height that you've got even more choices: bananas, elephant ears, oakleaf hydrangeas, hostas, rhododendrons. 

 

'Sky Pencil' also looks marvelous when in discussion with ornamental grasses of any height, with extra points if they're also variegated.  If you're growing 'Sky Pencil' at the front of a bed, it could erupt from a mound of variegated palm sedge, Carex muskingumensis 'Oehme'.  Or how about an entire grove of 'Sky Pencil' rocketing upward from a large bed of Miscanthus 'Morning Light' or Andropogon gerardii?  The latter has the additional talent of being showy all Winter, too.

Where to use it in your garden

As a single or multiple sentinel in a bed, 'Sky Pencil' could be sited at the front, the middle, or almost at the back.  Not fancy enough?  Also train the shrub into a simple topiary; see "Quirks and special cases" below.

 

As tall and very narrow hedge; like all hollies, 'Sky Pencil' is comfortable with pruning, whether it's regular or occasional, mild or drastic.  See "How to handle it: Another option—or two!" below.

 

In Zone 7 and warmer, as a formal exclamation point in year-round containers.

Culture

Any decent soil, in full sun to light shade.  If the soil can be acid and humus-rich—like you'd provide for your best rhododendrons and azaleas—so much the better.  Mulch is always appreciated, especially to lessen freeze-thaw temperature swings in the Winter.

How to handle it: The Basics

Unless you're gardening in Zone 7, plant 'Sky Pencil' only in the Spring.  Mulch well, and water if needed so the bush gets through its first Summer without drought stress. 

 

If you're establishing 'Sky Pencil' in the colder end of Zone 6, and even into Zone 5, enhance its hardiness by planting only where it has excellent Winter drainage (on a slope, no matter how slight), and where it has some buffering from the wind.  Larger shrubs nearby—deciduous or evergreen—are a help, as is any nearby building or fence.  Even so, spray the bush with antidessicant the first Winter. 

 

Allow for the bush's mature width and height in your choice of siting, then you'll never have to prune 'Sky Pencil'.  If there is any tip damage by the end of Winter, prune that off in early Spring.  Holly usually recovers strongly from Winter damage; it doesn't need to be pruned, but it sure seems to like it.

How to handle it: Another option—or two?

If you're planting 'Sky Pencil' as a hedge, planting every two feet is fine.  'Sky Pencil' will, nearly always, be container-grown, and establishes easily at any size available.  Don't worry about buying large plants; small ones will grow faster than you think, and in three years will look no different than the large ones.  You're pruning the plants into a hedge, remember, so the larger the plants are at planting, the sooner you'll probably have to start your pruning. 

 

Let the hedge-plants grow on their own for a full year, even two, before you start pruning.  In colder Zone 6 and into Zone 5, prune only in early Spring, before growth begins; you'll cut off any Winter kill, as well as give the shrubs the most time to produce new growth and harden it off before the next Winter.  If you prune in the Fall, the shrub won't get the extra bit of Winter protection that would be provided to the plants' interior by the foliage and small branches you'll be pruning off the exterior.  In warmer Zone 6 and into Zone 7, you can prune in late Fall or in Spring.

 

While all hedges should be pruned so that their tops are much narrower than the bottoms, this is especially helpful—and easy—with a hedge of 'Sky Pencil', whose habit is naturally narrow to begin with.  Pruned stems branch out in response, making the surface of the hedge more and more finely filled-in.  The more smoothly the hedge of 'Sky Pencil' slopes inward from top to bottom, the fewer the opportunities for snow to accumulate on the sides.  The narrower the hedge is at the top, the less the snow can accumulate there.

 

Even so, you may find that your 'Sky Pencil' hedge is prone to splaying open with heavy snow.  The easiest solution is to pound a length of rebar (economical and readily available at Home Depot) into the ground, at the center of the hedge, every eight or ten feet, including right at each end.  Pound at least a foot deep, preferably two.  If your hedge is eight feet tall, you won't need to get the ten-foot lengths of rebar cut.  The rebar will be hidden by the height of the hedge, and yet is very accessible each Fall in advance of Winter storms.  Starting two feet from the ground, weave twine between the shrubs, tying it to each rebar as you come across them.  When you get to the end, weave back the other direction, but crossing on the opposite side of each shrub, and angling a bit higher shrub-to-shrub.  You should be 18 to 24 inches higher by the time you get to the other end.  Weave back and forth like this until you reach within a foot of the top; finish with a horizontal pass only inches from the top. 

Quirks or special cases

You could grow 'Sky Pencil' into a simple topiary: A ball atop a column.  Because the shrub's height and bulk are created by many separate branches growing vertically from the base, it's easier to form the ball from several branches instead of just one. 

 

Because a narrow plant is more exciting the taller it gets—and a tall and narrow plant with a ball on top is more exciting still—you'll want to let your 'Sky Pencil' grow for a number of years before starting its training.  Ideally, let it grow until it's at mature height.  This could be eight, ten, or twelve years after planting.  Be patient.

 

The next Spring, tie the tallest three or four branches together at the point you'd like the bottom of the ball to originate.  With a more trunk-forming species, you'd form this top ball exclusively from growth from the trunk's tip.  'Sky Pencil' doesn't form trunk-like branches, though.  Plus, the growth is so naturally vertical that it could be a slow process to convince one branch to produce enough lateral growth for a ball of any width.  Forming the ball from the collective growth of several branches is the solution. 

 

If any of these branches that are taller than you'd like the top of the ball to be, tip them.  Then top all of the branches you didn't tie together; cut them to form the flat surface upon which the ball will appear to rest.

 

Let the shrub grow the rest of the season, but in Fall be sure to tie a firm but not strangling spiral of twine around the entire shrub, so it holds its shape through Winter snows; you can remove the spiral in Spring. 

 

Go over the topiary in Spring to clip out any Winter damage and, if necessary, tie-in any Winter-splayed branches.  Retie the branches that form the ball, so their increasing girth doesn't become pinched by an out-of-date tie.

 

After the topiary is more mature (and therefore a bit hardier), you can also do light pruning in late Fall, after there's no chance of encouraging new growth that would have no time to harden off before Winter.  Do any "structural" pruning only in the Spring, otherwise you'll have to look all Winter long at the bare stumps of the limbs you just pruned.

Downsides

Although Ilex crenata itself is impressively shade-tolerant, the growth in lower light is open and, often, bare from the waist down.  'Sky Pencil' is so dense, and is so attractive because of it, that it's not suited for much shade; it needs plenty of sun—ideally full sun—to maintain its natural habit. 

Variants

Japanese holly is one of the most important broadleaved evergreens for gardens in Zones 5, 6, and 7.  It was introduced to America during the Civil War and was cultivated in Japan for who-knows-how-many centuries before that.  No surprise, then, that across both cultures, there are many cultivars already—several hundred—and, always, more on the way.  Extending hardiness more and more reliably to the cold end of Zone 5 has long been a priority, and there are more than a few cultivars already that are, indeed, Zone 5.  Ask local nurseries which plants are particularly hardy where you garden.

 

Ilex crenata habit can be broad and flat-topped, narrow and upright, vase-shaped, wide and mounding, or fairly round.  Mature size can range from barely a foot in any direction to fifteen feet tall and twenty feet wide. Leaves can be smaller, narrower, wider, or longer.  With the exception of a few variegates and gold-leaved cultivars, the foliage is a dignified dark green—much darker than Ilex crenata's counterpart in all of these diversities, boxwood, whose leaves are noticeably lighter green.  Berries are black and not showy, except in a very few cultivars with yellow or white berries.  Even so, the berries are a secondary consideration; mature size, hardiness, and habit will always be primary.  

 

It would be difficult to have a garden without at least one cultivar of Japanese holly, and even modest gardens might have several.  So far, my Ilex crenata collection is skimpy indeed: Just six cultivars.  That, clearly, isn't sufficient! 

Availability

On-line and at destination retailers.

Propagation

By cuttings. 

Native habitat

Ilex crenata is native to Japan; 'Sky Pencil' is native to Japan also, where it was discovered in the wild.

Add comment


Security code
Refresh

 
 
FacebookTwitterRSS Feed

Subscribe to Email

join our mailing list
* indicates required