Birches (Betula spp.) – Landscape Trends

Periodicals and other sources of design information often acclaim new selections that show landscaping promise. Often continuous and realistic testing on these choices is minimal and ultimately selections fail to show original idealistic expectations.

Landscape gardeners need to carefully study individual birch species and cultivars to choose correctly those that will thrive in individual garden landscapes. Another factor to take into account along with publicity is how available selections are in the landscape gardening trade. Good sources of information include catalogs like that from Forest Farm Nursery that include a reasonably complete listing and descriptions of commercially available birches.

Physical factors to consider in selecting birches are:

• Planting Site;
• Plant Hardiness Zone; and
• Pest Susceptibility.

Site Selection

Birches grow quickly, which makes them desirable for new plantings. Birch trees thrive in cool, moist soils but need sun on their leaves most of the day. Unfortunately, poor site selection aligned with quick growth often lead to trees that fail to reach their potential height of 50′ or more. They literally begin to fall apart at an early age.

Heat and Pest Problems

Undesirable characteristics that also lead to short survival times include heat intolerance and pest susceptibility. Horticulturists actively seek birch variations that overcome these two shortcomings.

In the northeastern U.S., most birch species and cultivars grow best at low temperatures – realistically areas north of VA, the Carolinas and GA. Looking at the USDA Plant Hardiness Zones map, this means most birches do not grow well in zones above six or possibly seven.

Birches, as a group, have many fungus and insect problems. These include leaf spots, blisters, rusts and canker along with organisms that contribute to mildew, dieback and wood decay. Insects comprise aphids, birch skeletonizers, leaf miners, bronze birch borers and seed mite galls.

An Excellent Landscape Birch and Its Cultivars

River or Red Birch (Betula nigra): North American origin; Zones 4 – 9, medium to fast growing, 30′ to 40′ over 20 years; autumn color – yellow, not as good as some other birches; bark – gorgeous color, exfoliating gray brown to ivory to copper; usually multistemmed, may be trained with a single leader. Exceptional heat tolerance makes this birch and its cultivars adaptable in both northern and southern garden landscapes. River birch and its cultivars are not, however, drought tolerant and need continuous moisture. Michael A. Dirr in the 5th edition of Manual of Woody Landscape Plants: Their Identification, Ornamental Characteristics, Culture, Propagation and Uses, writes on p. 128 “probably the most trouble-free birch, except in moist years…significant leaf spot.”

• ‘Dura Heat™’ (Heat-tolerant River Birch) is a small-leaved selection from GA with excellent disease and heat resistance that extends growing range. A fast-growing large tree, 40′ tall, 25′ to 30′ wide, that thrives in wet soils and high water table.

• ‘Little King’ (Fox Valley® River Birch) is a compact dwarf that grows 8′ to 10′ in height with an equal or greater spread in ten years. It exhibits cinnamon-red and pale salmon exfoliating bark at an early age. Excellent heat tolerance.

• ‘Heritage®’ (‘Cully’ River Birch, an improved ‘Heritage®’) has earned. according to Dirr on p. 128, of the 5th edition of Manual of Woody Landscape Plants: Their Identification, Ornamental Characteristics, Culture, Propagation and Uses “a place in the birch hall of fame.” This cultivar is hardy to -40¬∞F and is well adapted to the heat of zone 8 and perhaps warmer. It begins with exfoliating white bark and as tree matures, darkens to salmon-white and matures to salmon-brown. Autumn leaf color is variable, but usually develops an attractive yellow. The Society of Municipal Arborists (SMA) chose Betula nigra Heritage (‘Cully’) as its 2002 Urban Tree of the Year.
• ‘Summer Cascade’ PPAF (Weeping River Birch) is a new, weeping form of river birch with a unique, pendulous habit of graceful arching branches. When untrained, the plant forms a mounded shrub or small tree with successive layers of arching branches. A handsome tree with pendulous branches also results from staking and training with a central trunk. Flexible new growth also makes the tree ideal for use in topiary. Extraordinary growth rate yields a 6′ to 8′ tall branched tree one growing season from a rooted cutting. The original plant, grown free-form is now, after 10 years, over 6′ tall and 10′ wide with the potential of reaching 60′. ‘Summer Cascade’ River Birch PPAF is a joint introduction by Shiloh Nursery, North Carolina State University and North Carolina Foundation Seed.
• Tecumseh Compact™’ (Compact River Birch), only about 12′ high x 12′ wide with pendulous branches, is an excellent focal point for a small landscape. It has cinnamon-colored exfoliating bark.