Sky Pencil Holly, Ilex crenata, is a stunning, broadleaved holly variety with gorgeous dark green foliage and a curious columnar growing habit.
With dozens of landscaping uses and a compact vertical growth habit, it might just function as the exclamation point you need in your garden or patio space.
Easy to care for, easy to grow, here is everything that you need to know about sky pencil holly.
What is Sky Pencil Holly?
Pencil holly is an evergreen plant that originates from Japan, hence the more commonly known name of sky pencil, Japanese holly.
Prized for its foliage, pencil holly made its first appearance in the U.S. in the 1980s and since has become a favored landscaping plant.
Sky Pencil holly is ideal for decks, patios, screening, hedging, and framing entryways.
Japanese Holly Varieties
There are fantastic varieties of Japanese holly that are great to consider. These include:
- llex Crenata “Halleri”. A smaller, dwarf variety great for indoors. This cultivar only grows 2-4 feet tall.
- Ilex Crenata “Dwarf Pagoda”. This is also a very small cultivar with dense, compact growth.
- Ilex Crenata “Convexa”. This variety is known best for its plump, black fruit. It’s tall growing and a great choice for gardens.
- Ilex Crenata “Lemon Gem”. This variety has distinct yellow foliage, which turns into a lime green during the summertime.
How to Grow Sky Pencil Holly
The sky pencil holly tree can grow fairly well both in pots and in the ground. This is what makes it so practical for smaller gardens and patio spaces.
Best suited for USDA zones 6 to 9, sky pencil holly can be kept outdoors during the wintertime but will need a little protection from frost.
Sky pencils need a good amount of sunlight throughout the day. However, it will need some protection from the harsh afternoon sun. Partial shade spots that receive morning sunlight are ideal.
In cooler areas, your sky pencil will need at least 6 hours of sunlight per day. The sky pencil holly tree grows best in loose, well-draining soil that has a slight acidity.
If you have sandy or clay soil, it is recommended to treat it with compost before planting. It is important to note that this variety of Japanese holly is an all-female cultivar, which is unimportant unless you want yours to bear fruit.
In order to have fruit-bearing trees, you will need to have a male variety in the vicinity.
Propagating Sky Pencil Holly
Most gardeners prefer buying smaller sky pencil trees from their local garden store. However, it can be propagated by means of a cutting.
- Remove a stem cutting approximately 2-3 inches in length.
- Dip the cut end into a rooting hormone and plant in a container with a mixed potting mix.
- Keep the container in a warm and sunny spot to root.
Sky pencil Japanese holly is incredibly slow-growing, so you can keep your cutting in the container for as long as 3 to 4 years.
Planting Sky Pencil Holly
Planting should be done during the spring, so your sapling has enough time to establish itself before the dormant season. Simply:
- Dig a hole that is 2 or 3 times larger than the root ball.
- Place the root ball inside and backfill.
- Using your hands or feet, press down onto the soil to remove any air pockets.
- Air pockets will inhibit the roots’ ability to draw in nutrients.
If you are planning on planting more than one tree in your garden, be sure to plant them at least 2 to 3 feet apart.
Sky Holly Pencil Care
Once your tree is established, it will require very little care. In the first year, you will need to water very regularly to help the roots establish themselves. After that, you can cut back to occasional watering.
It is a drought-tolerant plant, so you should forget from time to time, you won’t need to worry too much. Regular pruning can be done to maintain the shape of the tree if you want. This should be done during the dormant season in winter.
A 10-6-4 or organic fertilizer can be added during the spring from time to time.
If you’re keeping your sky pencil holly tree outdoors in the winter, you will need to protect it slightly from the frost. By tying up the branches in the winter, you can prevent frost burn and breakage.
Using a twine, wrap the tree from top to bottom to keep the branches tight against the tree.
Sky Pencil Holly Problems
It’s quite rare to have sky pencil holly problems unless the tree is growing in un-ideal conditions. The only issues you may come across include:
Thankfully, there is an easier name to say for this disease, only called die-back. The Botryosphaeria bacteria makes its way into the system of the holly through a broken branch of cut somewhere on a stem.
Once it is in the Sky Pencil’s system, the bacteria gets to work, infecting the bark and tissue. Soon, those areas collapse and turn black.
The fungus creates canker sore spots on the shrub that reduce the movement of water and movement through the stem and entire plant. Soon, the leaves turn yellow and fall off of the plant.
Once Botryosphaeria enters your shrub, your job is to prevent its spread from destroying your entire plant. Locate the infected stems and cut at least one inch below the canker. If you do this throughout the whole plant, you will stop the spread of the bacteria.
Gardeners should focus on trying to stop it from happening altogether by not overwatering the shrub and removing damaged branches. To help you with this task, check out our review on the best tree pruners for 2023.
Another sky pencil holly problem is web blight, officially called Rhizoctonia aerial blight. This disease happens when your plant is exposed to a lot of rainfall, high humidity and warm temperatures take place all at one time.
It is a fungal disease which loves moist, humid, warm environments to grow and spread. Web blight is a particularly frustrating problem because it spreads quickly.
Due to the excessive rainfall, you may not notice the spread until it’s taken a strong hold on your plant. Typically, the fungus starts growing on the plant’s lower leaves first.
Soon, you will notice the leaves on your plant turning brown and eventually black. The stem will have brown cankers near the soil.
How do you prevent web blight from taking over your Sky Pencil Holly?
It is important to plant your shrub in an area with a lot of drainages and air circulation. Each year, you should thin out its leaves, so it gets plenty of ventilation throughout the plant.
You should always water the bush in the morning, so it has plenty of time to dry before nighttime. Luckily, you can treat web blight with a simple fungicide every seven to 14 days until it's gone!
If you don’t protect the branches in the winter, you risk winter burn. You will notice the burn by a discoloration at the tips. This generally only happens in freezing temperatures.
Another problem faced by Sky Pencil Holly growers is a fungus referred to as leaf spot. You might notice oddly shaped, yellow spots on the leaves.
Gradually, these spots turn to a purple and black color. It is important to treat leaf spot quickly because the leaves will die and fall off of the shrub. When left on its own, leaf spot will remove all of the leaves on the bush.
Homeowners should only purchase these holly bushes from trustworthy sources for plants. Otherwise, you risk bringing home fungal spores that could spread across your entire garden beds!
Remove all debris from the ground surrounding your Sky pencil because it is a breeding area for fungus. Debris tends to hold onto moisture. Treating leaf spot isn’t that difficult.
You can purchase a fungicide and spray it on the infected area. Check the instructions on the treatment, but typically one tablespoon is recommended for one gallon of water.
You should treat the plant every ten to 14 days until it’s fully gone.
Root rot isn’t exclusive to just holly bushes. It happens when the soil is too wet, and it retains moisture. Oxygen is unable to penetration, leading to root rot. It is a fungal disease, causing the roots to turn brown or black.
Over time, they become mush and die off. Unfortunately, it will cause leaves to fall off and eventually, the entire plant can die! Preventing root rot is relatively easy. Planting these shrubs in the correct soil is important.
They require fast-draining soil that allows oxygen to move throughout. It is also important to never overwater these plants. Don’t water until the top one to two inches of soil is dry.
Sky Pencil Holly problems are typically easy to handle once you understand what is wrong. There is a treatment for everything! It is best to plant your Sky Pencil in the proper location with air circulation and correct soil to avoid the possibility of diseases.
Remember to keep the area surrounding the bush clear of debris to stop the spread of fungus!
These little pests are problematic because they come in colonies and spread incredibly quickly. These pests gather on the underside of leaves, sucking out the sap and turning the leaves yellow.
To treat, remove the infested leaves, spray your tree with a strong gust of water and then spray with a vinegar solution.
Sky Pencil Holly Companion Plants
Looking for some companion plants? Here are some of our favourite picks for plants that compliment sky pencil holly:
- False Holly
Wrapping Up Our Sky Pencil Holly Growing Guide
So, there you have it. Everything you need to know about the sky pencil holly tree: while it will need a little extra attention in the first year and during winter, it will grow beautifully and carefree throughout the rest of the year.