A giant among dwarf conifers

by Jon Hetman, Director of External Relations & Communications

January 31, 2018

Dwarf Alberta spruce

A giant among dwarf conifers

Dwarf Alberta spruce

Picea glauca var. albertiana f. conica (dwarf Alberta spruce) in the Leventritt Shrub and Vine Garden.

The discovery and introduction of Picea glauca var. albertiana f. conica is a remarkable example of horticultural discovery as happenstance. In 1904, staff members Alfred Rehder and John G. Jack took a stroll while waiting at a train station near Lake Laggan, Alberta, and noticed some unusual dwarf spruces growing nearby. They speculated that a spruce with a witch’s broom had dropped seeds and produced small, compact plants with tight foliage. As agents for the Arboretum, they couldn’t resist collecting their extraordinary find for further study, and so the plant made the cross-continental journey to the Arboretum with them.

Thus begins the horticultural tale of one of the most familiar and conspicuous plants in cultivation—the dwarf, slow-growing evergreen known popularly as dwarf Alberta spruce. Taxonomic studies conducted by Rehder established the plant as a naturally-occurring mutant of white spruce (P. glauca), a noble and highly adaptable conifer with distinctive blue-green foliage that exudes a musky scent when crushed. Unlike the species, which can attain a height of more than 100 feet in the wild, this form generally remains under 10 feet in height, growing slowly and rather uniformly in a cone shape. Its foliage is softer and denser than typical white spruce, with needles less than ½-inch in length and light green in color.

As a specimen plant, dwarf Alberta spruce has few disadvantages, rarely producing cones and amenable to creating topiary forms when grown in containers. Although the source plant has long since perished, its genetic advantages carry on in our living collections through two 85-year-old plants growing on Conifer Path and a much younger individual growing in the Leventritt Shrub and Vine Garden (pictured). Today a giant in the contemporary nursery trade, this diminutive gem is a living tribute to the lifelong work and legacy of Arboretum plantsmen like Rehder and Jack. It also provides a great example of opportunistic collecting when the right people are in the right place at the right time.

Learn more about conifers and the Arboretum’s collection of gymnosperms at our next Collections Up Close event in the Conifer Collection on Sunday, February 4 from 1:00-3:00pm.

Jon Hetman (published previously in Silva, Fall/Winter 2013-14)

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