Common Winterberry, Black Alder (Ilex verticillata)

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Plant Details

Category: Nursery
Light: Sun to Part Shade
Bloom Season: Spring
Height: 6-15’ / 
1.8-4.5m
Space: 6-12' / 
1.8-3.6m
Zones: 3, 4, 5, 6, 7, 8, 9
Lowest Temp: -40° to -30°F / 
-40° to -34°C
Colors: White

Basic Care

Plant in any sunny location in the garden. Best in fertile, humus-rich, well-drained soil. Prune in late winter or early spring before flower buds appear.

Water

Keep evenly moist; tolerates wet soil and periodic flooding.

Soil

Moist, acidic, organic-rich soil. Adapts to clay and poorly drained soils.

Feed

Apply compost in spring.

attracts pollinators

Attracts Pollinators

attracts birds

Attracts Birds

attracts butterflies

Attracts Butterflies

deer resistant

Deer Resistant

Native Plant

water loving plants

Water Loving

Looks Great in Winter

border plants

Borders

Features

Common winterberry is a deciduous holly native to eastern North America where it grows in swamps, damp thickets, low woods, bogs, and along ponds and stream banks. Unlike evergreen hollies, it drops its leaves in autumn, leaving the bright red berries highly visible on bare stems through winter. Plants form an upright to rounded, multi-stemmed shrub with toothed green leaves and small, inconspicuous greenish-white flowers from late spring to early summer.

Winterberry is highly valued for its heavy crop of colorful fruit and its usefulness in wildlife gardens. The berries provide an important food source for birds and small mammals in late fall and winter, and the flowers support pollinators. Plants are dioecious, meaning male and female flowers occur on separate plants, so at least one compatible male plant is needed nearby to pollinate female plants and produce berries.

The common name “winterberry” refers to the showy red berries that persist on the shrub into winter after the leaves have fallen. Note that the berries are mildly poisonous to humans and some domestic animals and should not be consumed by people or pets.

Uses

Excellent for native plantings, wildlife gardens, bird gardens, rain gardens, pond or stream edges, moist shrub borders, hedges, screens, foundation plantings, and winter-interest gardens. Great naturalized along the border of moist woodlands.

Common Winterberry, Black Alder (Ilex verticillata) Care Guide

Plant in spring or early fall to give plants the best start.

Choose a location that will allow roots to spread and branches to grow freely. Space plants far enough from building foundations, walls, and decks so that the growing foliage won’t crowd the structure. Consider whether tall trees or shrubs will block windows or interfere with the roof or power lines.

To prepare the planting area dig a hole as deep as the root ball and three times as wide. After removing the soil, mix it with some compost or peat moss. This enriches the soil and loosens the existing dirt so that new roots can spread easily.

To remove the plant from the container, gently brace the base of the plant, tip it sideways and tap the outside of the pot to loosen. Rotate the container and continue to tap, loosening the soil until the plant pulls smoothly from the pot. The container can also be removed by carefully cutting it down the side.

Set the plant in the hole. If the root ball is wrapped in burlap fabric this must now be removed along with any string or wire securing the burlap. If roots are tightly packed gently rake them apart with your fingers.

Return the soil to the planting area packing it firmly around the root ball. Fill the hole until the soil line is just at the base of the plant, where the roots begin to flare out from the main stem.

Water the plant well then add a 2” (5cm) layer of mulch, such as shredded bark, around the planting area. Keep the mulch at least 4” (10cm) away from the trunk of the plant as this can keep the bark too moist and cause it to decay.

Depending on rainfall, new plants need to be watered weekly through the first growing season. A slow, one-hour trickle of water should do the job. During hot spells thoroughly soaking the ground up to 8” (20 cm) every few days is better than watering a little bit daily. Deep watering encourages roots to grow further into the ground resulting in a sturdier plant with more drought tolerance.

To check for soil moisture use your finger or a hand trowel to dig a small hole and examine the soil. If the first 2-4” (5-10cm) of soil is dry, it is time to water.

Monitor new plants through the first two years to make sure they are getting the moisture they need. After that they should be sturdy enough to survive on their own.

Pruning may be needed to remove dead branches, encourage bushier growth, promote more flowers, or maintain a specific size or shape.

Dead branches should be removed close to the trunk, flush with the bark. When pruning to control a plant’s size or shape, cuts should be made just above a leaf bud and at a slight angle. This bud will be where the new growth sprouts.

Many shrubs can be regularly sheared to keep them shaped as a hedge, edging or formal foundation planting.

Always use sharp, clean tools when pruning. There are many tools available depending on the job. Hand shears, pruners, and loppers are ideal for most shrubs. Pole pruners and tree saws are better for large, mature shrubs or trees. If a tree is so large that it can’t be safely pruned with a pole pruner, it is best to call in a professional tree service.

Established trees should be fertilized every 2-3 years. Feed in early spring when plants start growing.

Fertilizers are available in many forms: granulated, slow-release, liquid feeds, organic or synthetic. Determine which application method is best for the situation and select a product designed for trees and shrubs, or go with a nutritionally balanced, general-purpose formula such as 10-10-10.

Always follow the fertilizer package directions for application rates and scheduling. Over-fertilizing plants or applying at the wrong time during the growing season can result in plant injury.

Common Winterberry, Black Alder Companion/Combination Plants

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