How To Grow The Sky Pencil Holly (Ilex crenata)

This is one of my favorite evergreens because it literally stands up like an exclamation point and announces itself to all passersby. The name Sky Pencil Holly (Illex crenata) is an apt descriptor. The distinctive shape wants to be used in a bold landscape or as a striking hedgerow. The fact that it is super easy to grow only makes it that much more attractive as a holly. If you are the type of person who likes your garden to make a statement, the Sky Pencil Holly is for you.

While this shrub looks best rising up out of an outdoor landscape, it can also be grown in a container. With large enough containers, it can still grow to its full height of 10 feet and make sure no one misses seeing it. Two Sky Pencil Hollies look amazing as a frame for a doorway or at the entrance to a driveway. They also look great placed on decks or patios or as foundation plantings. They stand out when arranged in pairs to flank a statue or wall.

Originally from Japan, the Sky Pencil Holly was introduced into the U.S. National Arboretum in 1985. It is a cultivated variety of Japanese holly, is classified as a broadleaf evergreen shrub, and is part of the boxwood evergreen family. The plant is native to thick forests and mountain slopes in Japan, Korea, China, and eastern Russia and stays green all year.

How To Grow The Sky Pencil Holly

Description of Sky Pencil Holly

The Sky Pencil Holly grows up to 10 feet tall and is broad at the top, with its branches tapering off towards the bottom. It will not grow wider than two feet at its deepest, and it can be pruned to be even narrower. It is a great choice for spaces where there isn’t room for larger plants. This is actually one of its main draws. There aren’t many shrubs that offer the visual appeal that this one does without taking up huge amounts of space.

It has small, light, undistinctive green flowers and little blackberries. Neither of these is as attractive or remarkable as its shape. The Sky Pencil Holly has small, oval, green leaves that stay this color year-round, like all evergreens. A big bonus of this evergreen holly, however, is that it doesn’t have prickly leaves like so many other hollies do. The leaves and berries of the plant are poisonous and must be kept away from children and dogs. It can cause vomiting and diarrhea if ingested due to the presence of ilicin, a toxic substance. The birds like the berries, though.

The majority of people use Sky Pencil Holly for hedgerows. I like them for this, however, my favorite planting of these is as single shrubs, standing out in the landscape and yelling, “Look at Me!” I think too often we want our landscapes to meld and merge together. We want a nice, cohesive blending of plants and flowers and ignore the uniqueness of each one. If you are going to plant Sky Pencil Holly, think about what kind of statement you want to make. A long row of rosebushes, perhaps, accentuated at the end with a giant exclamation shrub? Or an arrangement of flowers with one or two Sky Pencil Hollies bursting up through the center?

Sky Pencil Holly is an excellent option for privacy screens because it can grow in tight spaces and form a dense barrier. To create a solid screen, you can plant the trees with a spacing of less than 2 feet. Besides, this shrub is also used in a lot of functional settings. They are useful to camouflage rain gutter downspouts, central air conditioning units, and other unsightly things found in office parks and around buildings.

The Sky Pencil Holly lives for approximately 40 years, so plan your landscape with its longevity in mind.

Propagation and Cultivation of Sky Pencil Holly

The Sky Pencil Holly can be planted outdoors in USDA plant hardiness zones 6–9. And luckily for those of us who live in colder climates, it does really well growing in a container as well. In a container, it can be kept outside during the temperate months and then relocated to a more protected space when the cold and snow begin. It is super nice to have the rich green foliage of this plant to gaze at while the world around you descends into snow and cold. The offset of colors is remarkable.

This shrub grows slowly but impressively. It may even seem like it isn’t growing much in the first few years, but it is, just at its own pace. The impressive part is that even though it is small, it keeps its upright, ‘at-attention’ stance, making a statement at all times, it seems.

Starts, or cuttings, for the Sky Pencil Holly can be obtained from your local garden center or online. The size of the order isn’t as important as making sure you buy from a reputable supplier. Once they are fully grown, in about 3 years, they will all look the same.

Growing in the Ground

Planting the Sky Pencil Holly is super easy. It should only be planted in the spring in a location that gets good drainage. A slight slope is always a good choice. This super easy-going shrub does well in a variety of soils as long as they drain well. It prefers a slightly acidic, moist, soil, but it adapts easily to a wide variety of soils.

Once you’ve picked the perfect location, dig a hole in the ground that is as deep as the root ball and three times wider. At this point, it is good to add some compost to the hole to enrich the soil and make for better growth. Put the plant in the ground and cover it firmly. Use your foot to compress the soil around it and remove any potential air pockets. Air pockets prevent all parts of the root from touching the soil, which isn’t good because the roots get their needed nutrients from the soil.

If you are planting a row or border of Sky Pencil Holly, allow 2–3 feet between bushes. This will allow the bushes to touch without overcrowding each other. Of course, if you’d like them spaced farther apart, that is also fine.

After planting, water the Sky Pencil Holly thoroughly and regularly until it gets established and begins growing. It should be noted that growing the plant from seed can take years due to the slow germination of the seed and is not recommended.

Growing in a Container

The cutting or plant start will likely come in a container from the gardening store. It can simply be kept in this pot while it grows and located someplace where it will get good amounts of sun.

Because the Sky Pencil Holly is such a slow grower, it will do quite well in a container for up to 3 years. When it starts to get closer to its full height, however, something else will have to be figured out if it is located in a space that can’t accommodate its height. Once it has outgrown the original container, this evergreen can be moved to a larger, permanent, one, or it can be planted in the ground.

In cold climates, evergreens in containers are especially susceptible to drying out. Their growth slows down a lot, yet they don’t go completely dormant, so it is important to ensure they are getting adequate moisture.

Care for Sky Pencil Holly

A little pruning here, a little fertilizing there, and that’s it. The small amount of care that this evergreen needs is fabulous, especially for those of us (me!) who are too busy and way too forgetful. We all need plants like this in our landscapes. Even if you completely forget about it, the Sky Pencil Holly will just keep doing its thing and grow tall and proud. But if you follow the tips given below, your Sky Pencil Holly will grow faster.

Climate

The Sky Pencil Holly prefers sunny locations. It also does well in partial shade. It all really comes down to where you live. In USDA hardiness zones 8 and higher, it is best to locate the Sky Pencil Holly in partial shade so it doesn’t burn. In zones 6 and 7, it can be located in a place with full sun or a little bit of shade.

There have been reports of folks in Zone 5 growing the Sky Pencil Holly with success by planting it in full sun. The south or west side of the house is best for this since it receives more sun than the north or east sides. A spot sheltered from the wind is also best. Planting them in a pot makes for easy relocation indoors during the harsh winter months to protect the plants from strong winds.

If you are planting this shrub in places where there is snowfall, it will need to be tied up during the winter to prevent the branches from breaking. A length of twine spiraled up from bottom to top and then back down to the bottom again will keep the branches tight to the trunk and protected. This will require a step ladder once the plant reaches its full height. A layer of mulch around the base of the bush will also go a long way toward protecting the roots during frosty weather.

Watering

During the first year, water this plant deeply and consistently so it can establish its vast root system.

Once a Sky Pencil Holly is established, it only needs watering during dry spells. How awesome is that?! It can even tolerate a mild drought without too much wear and tear.

Sun

The Sky Pencil Holly likes full sun in zones 5-7 and partial shade in zones 8–9.

Fertilizing

Every spring, this evergreen will benefit from an application of fertilizer. A 10-6-4 blend or one made specifically for broadleaf evergreens is best. One pound of fertilizer per inch of trunk diameter is recommended. Once the fertilizer has been applied, water the Sky Pencil Holly well so the fertilizer will sink in.

Pruning

The Sky Pencil Holly doesn’t need to be pruned to keep its unique shape. However, it likes to be pruned on a regular basis to keep its shape trim and uniform. This is especially important if you have a row or cluster of them. They will begin to look like slightly shaggy exclamation points if allowed to grow as they please. They tolerate unique and fun pruning as well, and they can be cut and maintained in a variety of shapes.

This evergreen grows up to 10 feet tall and 2 feet wide. It can be trimmed down to 6–8 feet if desired, and the sides can be pruned to be narrower as well. They should always be pruned in the winter when they are dormant.

Potential Problems of Sky Pencil Holly

The other incredible thing about this plant is that it rarely suffers from pests or diseases. There is, of course, some possibility of problems, but armed with some knowledge beforehand, you should be able to counteract them.

Pests

Spider Mites: These tiny little creatures are hard to see individually, but they live in colonies, so when you do see them, you know you have a problem. They are more prevalent in hot, dry, climates. Spider mites drink the sap from leaves and stems, leaving tiny feeding marks on the leaves. Eventually, the leaves will turn yellow, dry up, and drop off. It is not recommended to use an insecticide since that usually kills off the spider mite’s predators as well, and then you have an even bigger problem. Instead, remove infested leaves or plants to prevent their spread. Also, so as not to encourage them to take residence in the first place, take any pruned debris away from the area and throw it away.

Diseases

Black Rot: This awful fungal disease causes leaves to yellow and drops off. The leaves and stems will start to die off, as well. It can stunt the growth of the plant, and if it isn’t discovered in time, it will kill the plant. Young Sky Pencil Hollies and established ones are both susceptible to this disease. If the plant is dropping leaves, it is generally too late to save it, and experts recommend removing and destroying it so the disease doesn’t spread to other specimens. This disease can live in the soil, so avoid planting another holly in the same place as it will likely suffer the same fate.

Leaf Spot: This is another fungal disease, and it looks quite similar to black rot. The difference is that with leaf spot, actual yellow spots appear on the leaves, instead of an overall yellowing, which is what happens with black rot. The spots will grow larger and turn brown, and then leaves will start to fall off and new shoots will die. This disease can be treated with a fungicide application every 10–12 days.

Other Issues

Winter Burn (only an issue in climates with freezing temperatures): Winter burn causes needle discoloration at the tips. As it progresses, the discoloration moves from the tip down further to the leaves at the base of the stem. Winter burn is caused by three overlapping conditions: freezing temperatures, high winds, and low soil moisture. The Sky Pencil Holly in these conditions will not be able to replace any moisture it is losing fast enough because the ground is frozen. To prevent Winter Burn, make sure the evergreen is receiving adequate water, that it is shaded from the wind, and that there is mulch around the base to help retain moisture.

Conclusion

The Sky Pencil Holly makes a bold and dashing addition to any home garden or landscape. It is beautiful in its evergreen color and distinctive shape. The versatility of it for use as a border, presentation, or statement piece is only made better because of its simplicity and undemanding nature.

Resources

University of Arkansas, Division of Agriculture, Cooperative Extension Service, Sky Pencil Holly

https://www.uaex.edu/yard-garden/resource-library/plant-week/holly-skypencil-6-4-10.aspx

Missouri Botanical Garden, Sky Pencil Holly

http://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=v890

University of Florida, IFAS Extension, Hollies

https://edis.ifas.ufl.edu/publication/mg021

Samuel Ade
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