Evergreens Suitable for Hedging: A Toronto Master Gardeners Guide

White cedar or arborvitae (Thuja occidentalis) makes an excellent, fine-textured evergreen hedge. Photo: Helen Battersby

Hedges are a functional feature in many gardens. They can be small or large, formal or informal. They can also function to break a long garden into smaller units, to define a space or to provide a visual barrier or windbreak. This gardening guide highlights a number of varieties of evergreens that can be used for hedges.  It also suggests common sense, ecologically sound solutions for potential pest and disease problems for each type of hedge.

Planting

Where possible, buy container grown or burlap and balled plants for your hedge that are all of similar size and height. They will have a greater success rate than bare-rooted plants. If you are planting bare rooted specimens, make sure that the root balls are kept wrapped, moist, and in the shade until they are planted.

Dig a trench 40cm wide and the length of the planned hedge. Work in some phosphate or bone meal to encourage root development. Plant the trees branch to branch. Add an inch or two of composted organic matter as top dressing, allowing soil microorganisms to incorporate the organic matter as needed. Cedar hedging can be planted in double rows and staggered for fuller result. For a dwarf formal hedge (under 1 m) plant 3 trees per metre.

For a hedge with an even height, prune the tip of the shortest plant by 1/10 of its height and then prune all others down to this height. Pruning off the tops will encourage the trees to fill out and will result in a thicker hedge. Always prune a hedge slightly narrower on top to allow even light penetration and prevent snowfall damage.

Water thoroughly after planting and until the plants become established in the first year. Continue to water until the ground freezes.

Recommended Varieties

Eastern White Cedar

Thuja occidentalis (Eastern White Cedar) is hardy to Zone 2. Consider field grown specimens, as they are usually more economical and offer single stemmed specimens. These native plants are versatile, will thrive in sun or part shade, require neutral to alkaline moist soil and prefer good drainage.

Cultivars

T. occidentalis ‘Degroot’s Spire’ height 3-4m, spread 1.2m

T. occidentalis ‘Nigra’ height to 5 m, spread to .5m fast growing with dark green foliage

Pruning

Upkeep trimming in June: to keep the hedge straight, tie a string between 2 posts at either end of the hedge to use as a guideline for pruning. Keep the bottom of the pruned hedge slightly wider than top.

Pests/Diseases

Caterpillars, mites, leaf miners and scale are common pests. Needle blights are common diseases.

Integrated Pest Management

To control over-wintering mites, spray in early April with dormant oil or apply insecticidal soap during the growing season. Injury from leaf miners can normally be controlled by pruning off the affected portion. Blight is common on cedars under stress from environmental factors including freezing and sunscald.

Juniper

Juniperus spp. (Juniper) is hardy to Zone 4.

Cultivars

J. chinensis ‘Mountbatten’ height to 6 m, spread to 2m, sun, rapid growth with silver green foliage

J. chinensis ‘Spartan’ height to 4m, spread to 1.25m, sun and part shade

Pests/Diseases

Leaf miners, bark beetles, scale, and caterpillars are potential pests. Rust and blight are also common.

Pruning

Young junipers can be lightly sheared to make them thicken out. Do not trim into the hard wood.

Integrated Pest Management

Cedar-Apple Rust is a fungus that infects and alternates between a juniper and apple trees growing within several hundred metres of each other. Solution is to not plant these trees within these distances. Remove any galls as soon as they appear in late summer. Bark beetles are attracted to trees under stress. Water trees during drought and fertilize if growth is substandard.

Spruce

Picea spp. (Spruce) is hardy to Zone 3. Native

Cultivars

P. glauca ‘Conica’ (Alberta dwarf) height 4m, spread 1.5m Neat cone shape. Makes a good formal hedge.

Pests/Diseases

Sawfly, mites, bagworms and scale are common. Diseases may include rust.

Pruning

Very minimal as growth is slow.

Integrated Pest Managment

Bagworms can be picked off by hand or Bacillus thuringiensis (BT) can be sprayed (may need repeat application). Mites are most common in hot weather especially if tree is close to a surface that reflects heat. Use insecticidal soap spray.

Yew

Taxus spp. (Yew) is hardy to Zone 4. Will tolerate shade or sun.

Cultivars

T. media ‘Hicksii’ height 2.5m, spread 1 m. Upright columnar form, dark green foliage with inedible red berries

T. media ‘Densiformis’ height 2 m. A slow growing compact cultivar ideal for low hedge

T. cuspidata ‘Aurescens’ height/spread to 1.5m. Green needles with bright gold tips, plant in full sun for best color

Pests/Diseases

Black vine weevil and scale are common.

Pruning

Trim in early spring before new shoots emerge.

Integrated Pest Management

Black vine weevil are nocturnal and do damage by feeding on leaves and roots during life cycle. Indicators of this pest include crescent shaped notches found on needles. Handpick at night. Pull back mulch to allow soil to dry out as weevils need moisture to survive. Introduce beneficial nematodes, when soil is at least 10C. Soil must be kept moist for nematodes to survive.

Boxwood

Buxus spp. (Boxwood) is hardy to Zone 4. Boxwood will grow in sun or shade and makes a good small hedge.

Cultivars

B. ‘Green Mountain’ Height 1.5m, spread 1m. Upright with dark green foliage

B.’Green Velvet’ Height 1m, spread 1m. Retains rich green color in winter

B. microphylla koreana ‘Winter Beauty’ Height 1.25m, spread 1m. Rich blue green foliage all year

Pests/Diseases

Boxwood psyllid, leafminer, scale and mites are potential pests.

Pruning

Slow growing, annual pruning to maintain shape

Integrated Pest Management

Root rot may appear if planted in compacted or poorly drained soil. For control of mites, scale and psyllid, use horticultural oil or insecticidal soap sprays in early spring before plants put on new growth. Plants with a heavy infestation of scale may require pruning.

References

Cole, Trevor. The New Ontario Gardener. Toronto/Vancouver: Whitecap Books, 1991.

Date revised: September 6, 2010

For printable version, click:  Evergreens Suitable for Hedging – A Toronto Master Gardeners Guide

Produced by the Toronto Master Gardeners, these Gardening Guides provide introductory information on a variety of gardening topics.

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