Maine conifers resist deer advances

Cornell horticulture professor Mark Bridgen has a list of 87 plant species that he will guarantee deer will not eat. His list, published in American Nurseryman (Aug. 15, 2008), is based not on scientific research but on 22 years of gardening in Connecticut and New York.

Eleven of the 20 trees and shrubs on the list have prickly leaves or stems, including white spruce, Picea glauca, and common juniper, Juniperus communis, two conifer species native to Maine. Anyone who has tried to shake hands with a white spruce or common juniper will understand the deer’s point of view.

Use of white spruce in the deer-resistant garden is limited by its large size; a mature tree can be 60 feet tall and 20 feet wide. And the use of common juniper is limited by its low sprawling growth habit and tendency to turn brown in the winter. The garden worth of each species, particularly for small gardens, is realized in the numerous slow-growing cultivars that are available.

There are at least 15 cultivars of white spruce, my favorite among Maine’s native spruces for the blue-green needle color of some trees. Among the slow-growing forms is ‘Conica,’ the classic Alberta spruce, the most popular conifer in cultivation. A perfectly conical, small tree with a thick coating of fine, green needles, ‘Conica’ grows only 3 to 6 inches per year, 3 to 5 feet in height over 10 years. I often see this cultivar used as a foundation plant, a matched set of green cones framing the door.

Among the bluest of white spruce cultivars is ‘Cecilia,’ a rounded shrub with stout blue-gray needles. It grows at the same rate and reaches the same height after 10 years as ‘Conica.’ Its rounded habit and rigid form make it perfect for the rock garden or border.

An outstanding weeping selection of white spruce, ‘Pendula,’ has a narrow conical shape with pendulous, stiffly held, drooping branches bearing gray-green foliage. This tree grows a foot or less per year, reaching 8 to 10 feet in 10 years. Distinctive in its formal habit, it makes a dramatic statement in the garden.

Cultivars of common juniper include ‘Sentinel,’ a vertical form of the low sprawling species. It reaches only 7 feet tall in 14 years. The form is very tight, approximately 1 foot wide at the base, rising to a point. ‘Sentinel’ can be grown in a patio container, planted on each side of a door, or in groups of three in the garden.

J. communis ‘Gold Cone’ is similar to ‘Sentinel,’ grows a little faster and offers a year-round bright yellow foliage color that illuminates the winter garden. A third strongly vertical cultivar, ‘Compressa,’ resembles a tapered candle with silver green needles. A true miniature, reaching only 3 to 5 feet in 10 years, ‘Compressa’ makes a strong vertical accent in confined spaces or in containers.

The above descriptions represent a small fraction of the cultivars available for each of the two species. Gardeners interested in all of the possibilities should perform a Google search for images, using “Picea glauca cultivars” (or “Juniperus communis cultivars”) as key words.

Garden centers and nurseries are likely to label these and other slow-growing conifers as “dwarf conifers,” a term that is misleading. Over the long haul, any of these cultivars can become as large as the species. Just not in your lifetime.

Send queries to Gardening Questions, P.O. Box 418, Ellsworth 04605, or to rmanley@ptc-me.net. Include name, address and telephone number.