Sky Pencil holly

Sun

Full sun to partial shade; light afternoon shade helps in hot climates.

Water

Keep the root zone evenly moist but not waterlogged. Water during dry spells, especially while establishing and when growing in containers.

Soil

Moist, well-drained, acidic soil enriched with organic matter. Alkaline soil can cause yellow leaves, and poorly drained clay encourages root rot.

Height

6-10 ft (1.8-3 m)

Spread

2-3 ft (0.6-0.9 m)

Flowers

Small, inconspicuous white flowers in late spring to early summer.

Foliage

Evergreen. Small, glossy, dark green leaves with finely scalloped edges; held on strongly upright branches.

Growth

Slow to moderate.

Care needed

Low

• Pollinators
• Wildlife
• Low allergen

Northern hemisphere months. In Australia, shift them by six.

Difficulty

Moderate

Toughness

Fairly tough

Pick your zone, country, light and whether you have pets.

1. Planting day

   1.6 ft (0.5 m)

2. After 1 year

   2.6 ft (0.79 m)

3. After 2 years

   4 ft (1.1 m)

4. After 3 years

   5 ft (1.4 m)

5. After 5 years

   6 ft (2 m)

About 7 years to full size.

From a typical nursery size, at an average rate for this kind of plant. A rule of thumb, not a forecast.

Cats and dogs

Toxic

Invasive in

the US

Growth rate

Slow

• Water deeply through the first two growing seasons whenever the root zone begins to dry.
• Apply 2-3 in (5-8 cm) of organic mulch, keeping it clear of the stems.
• Feed lightly in spring with a fertilizer for acid-loving shrubs if growth is weak; avoid heavy feeding.
• Choose a sheltered position in colder areas. Although Japanese holly reaches zone 5, 'Sky Pencil' is less dependable there than in zones 6-8.
• Use a large container with drainage holes and protect container roots from severe winter cold.
• Brush off loose snow gently; where heavy snow is common, loosely bind the branches before winter to reduce splaying.

Pruning. Prune in late winter or early spring, removing dead wood and shortening branches that spoil the narrow outline. Avoid routine shearing or cutting the main upright shoots unless you need to limit height.

Late winter

Remove broken or dead branches and make any light shaping cuts before new growth begins.

Spring

Plant while conditions are mild, refresh mulch and feed lightly if needed.

Late spring

Check new growth for scale insects and inspect yellowing leaves for drainage or soil-pH problems.

Summer

Water deeply during dry periods; check container plants frequently.

Autumn

Water before the ground freezes if rainfall is low, and check that winter drainage is clear.

Winter

Protect exposed container plants and gently remove loose snow before branches spread apart.

• Plant a matching pair beside an entrance for a narrow evergreen frame.
• Repeat individual plants along a path or wall to create a regular vertical rhythm.
• Use as a slim backdrop to rounded shrubs and low perennials in a small border.
• Grow in large containers on a sheltered terrace, with low planting around the base.
• Plant a row for a narrow evergreen screen where the mature height is sufficient.

Garden styles it suits: Architectural minimal, Contemporary minimal, Formal, Japanese, Small-space and Winter interest.

Plant it with: Japanese skimmia, Pieris, Azaleas, Hostas, Japanese forest grass and Coral bells.

Wildlife: The small flowers attract bees and other insects. This is a female cultivar; a compatible male Japanese holly nearby is normally needed for black berries, which birds may eat. Its dense foliage provides cover.

• Root rot: plants wilt or die back in saturated soil. Improve drainage before planting and replace badly affected plants rather than repeatedly watering them.
• Yellow leaves from alkaline soil: test the soil pH and correct the growing conditions; use an acidic container compost where the garden soil is unsuitable.
• Scale insects: inspect stems and leaf undersides, remove small infestations by hand and use a locally approved horticultural oil when appropriate.
• Winter scorch or branches splaying under snow: provide shelter from drying winds, maintain autumn moisture and loosely bind branches before heavy snowfall.

Treat the berries and leaves as toxic to people, cats, dogs and horses. Eating them can cause vomiting, diarrhoea and abdominal pain; berries are the main ingestion risk. Seek medical or veterinary advice after significant ingestion.

Where it spreads. Japanese holly is listed as invasive in Virginia, United States. 'Sky Pencil' is a female cultivar and can produce bird-dispersed seed when a compatible male grows nearby; choose a different shrub where Japanese holly is locally discouraged.

• Fastigiate Japanese holly (Ilex crenata 'Fastigiata')

  Usually develops a broader, more substantial upright outline than 'Sky Pencil'; check the cultivar label because young plants can look very similar.

• Graham Blandy boxwood (Buxus sempervirens 'Graham Blandy')

  Also forms a narrow evergreen column, but its leaves grow in opposite pairs; Japanese holly leaves alternate along the stems.

• Irish yew (Taxus baccata 'Fastigiata')

  Has narrow, needle-like leaves rather than the small, broad, scallop-edged leaves of Japanese holly.

Ilex is the Latin name applied to holly, crenata refers to the scalloped leaf edges, and 'Sky Pencil' describes the cultivar's slim, upright shape.

Propagation. Take semi-ripe cuttings in late summer and root them in a free-draining medium under humid conditions. Seed does not reliably reproduce the cultivar's narrow shape.

Accepted botanical name

Ilex crenata

In the US and Canada

Introduced in the lower 48 states.

Native range

Assam, China North-Central, China South-Central, China Southeast, East Himalaya, Hainan, Japan, Korea, Kuril Is., Myanmar, Nepal and Sakhalin.

Measured

Soil pH 4.5 to 5.5. Average height 305 cm.

Sources: GBIF (CC BY 4.0), USDA PLANTS and Trefle (CC BY 4.0). The care and design notes are LandscapeGPT's own.