Shamrock inkberry

Sun

Full sun to partial shade; growth is usually densest with at least 4-6 hours of direct sun.

Water

Keep the root zone evenly moist, especially during establishment. Established plants tolerate brief dry spells but perform poorly in prolonged drought.

Soil

Acidic, humus-rich soil, ideally around pH 4.5-6.0. Tolerates clay and periodically wet ground, but avoid permanently stagnant conditions and chalky or alkaline soil.

Height

3-4 ft (0.9-1.2 m), occasionally taller with age

Spread

3-4 ft (0.9-1.2 m), widening further if suckers are retained

Flowers

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

Foliage

Evergreen. Small, glossy, dark green leaves with smooth lower margins and a few shallow teeth near the tips; no sharp holly spines.

Growth

Slow to moderate

Care needed

Low

• Pollinators
• Deer resistant
• Cold hardy
• Heat tolerant
• Wildlife
• Low allergen

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

Difficulty

Easy

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

   1.9 ft (0.58 m)

3. After 2 years

   2.2 ft (0.67 m)

4. After 3 years

   2.5 ft (0.75 m)

5. After 5 years

   3 ft (0.92 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

Native to

the US and Canada

In the garden

Spreads vigorously: plan to contain it.

Growth rate

Slow

• Water deeply during dry spells for the first two growing seasons; do not let the root ball dry out.
• Apply 2-3 in (5-8 cm) of organic mulch, keeping it clear of the stems.
• Test soil pH before planting; choose another shrub if your soil is strongly alkaline.
• Feed lightly in spring with a fertilizer for acid-loving shrubs only if growth is weak or a soil test indicates a need.
• Remove unwanted root suckers to keep the clump within its allotted space.

Pruning. Prune in late winter or early spring, removing dead wood and selectively shortening long shoots rather than repeatedly shearing the surface. Older, bare plants can be cut back hard before growth starts, but recovery takes time and flowering will be reduced.

Late winter

Remove dead or damaged branches and selectively thin crowded growth before new shoots emerge.

Spring

Plant when the ground is workable, water thoroughly, and renew mulch without covering the stem bases.

Late spring

Check flowering overlap with a nearby male inkberry if you want berries.

Summer

Water during prolonged dry weather and check yellowing plants for dry roots or unsuitable soil pH.

Autumn

Remove unwanted suckers and water well before winter if the soil is dry.

Winter

In cold, exposed gardens, protect young plants from drying winds and avoid de-icing salt near their roots.

• Plant as a low, informal evergreen hedge along paths or property boundaries.
• Use in foundation beds with room for its natural rounded shape rather than tight clipping.
• Group with azaleas and ferns at a moist woodland edge for year-round structure.
• Mass on the upper margins of a rain garden, where soil is periodically wet but not permanently submerged.

Garden styles it suits: Traditional, Woodland, Wildlife garden, Low-maintenance, Green on green and Winter interest.

Plant it with: Summersweet, Virginia sweetspire, Azaleas, Mountain laurel, Cinnamon fern and Foamflower.

Wildlife: Flowers attract bees and other small pollinators. Black berries on pollinated female plants provide food for birds, and dense foliage offers shelter. A male Ilex glabra is needed for reliable fruiting; another female 'Shamrock' will not supply pollen.

• Yellow leaves with green veins often indicate iron chlorosis in alkaline soil; test pH and move the plant to suitable acidic ground rather than relying on repeated iron treatments.
• Sparse lower branches develop with age, shade or repeated surface shearing; improve light and selectively rejuvenate older stems in early spring.
• Root rot can occur in stagnant, poorly aerated soil; improve drainage and replace severely affected plants.
• Spider mites may cause stippled or bronzed foliage during hot, dry weather; maintain soil moisture and rinse leaf undersides with water.

Not edible. Holly berries and foliage contain compounds that can cause poisoning in people, cats, dogs and horses, usually involving vomiting, diarrhoea or abdominal discomfort. Berries are the main ingestion risk; seek medical or veterinary advice after a significant ingestion.

• Japanese holly (Ilex crenata)

  Its leaves usually have fine, rounded teeth along most of the margin; inkberry leaves are mostly smooth-edged, with teeth concentrated near the tips.

• Boxwood (Buxus sempervirens)

  Boxwood leaves grow in opposite pairs, while inkberry leaves alternate along the stems.

• Dwarf yaupon holly (Ilex vomitoria)

  Yaupon has rounded teeth along much of each leaf edge and red fruit on female plants; inkberry has mostly smooth lower leaf margins and black fruit.

The species name glabra means smooth or hairless, while inkberry refers to the plant's ink-black fruit.

Propagation. Root semi-ripe cuttings in summer to retain the cultivar's characteristics, or lift well-rooted suckers during the dormant season. Seedlings will not reliably resemble 'Shamrock'.

Accepted botanical name

Ilex glabra

In the US and Canada

Native in Canada and the lower 48 states.

Native range

Alabama, Arkansas, Connecticut, Delaware, Florida, Georgia, Louisiana, Maine, Maryland, Masachusettes, Mississippi and New Hampshire.

Measured

Soil pH 4.5 to 7. Average height 220 cm.

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