February in the Garden 2023

Calocedrus decurrens

Following the last couple of months’ blogs on Southern Hemisphere conifers, the February instalment is an introduction to western North American conifers in the cypress family (Cupressaceae). Many of these trees and shrubs are familiar to Vancouver residents, as a number are southern BC natives—yellow cedar and western red cedar, the common and horizontal junipers, and Rocky Mountain junipers, for example. But further to the south—especially beyond where the Pleistocene glaciers of the last Ice Age terminated—the diversity of this family becomes considerable. It is worth considering that while there are six cypress family members native to BC, there are twenty-one in California. This southern diversity is reflected to some extent in the plantings of the Pacific Slope Garden as well as in the North American section of the E.H. Lohbrunner Alpine Garden. Botanical Garden staff have collected seeds extensively in the Siskiyous Mountains for these areas. The Siskiyous are a highly biodiverse range on the border of California and Oregon where a good deal of the cypress family diversity can be found.  

Many of BC’s native conifers, including most of the cypress relatives, can be found in the BC Rainforest Garden. A moderate-sized western red cedar, Thuja plicata, greets visitors beside the education pod (the “Cedar Pod”) near the entrance. As the interpretive signage indicates, western red cedar is known as the cornerstone of northwest coast First Nations culture. First Nations peoples used the wood, limbs, roots and bark to make innumerable products, from masks, boxes, clothing, utensils and cradles to totem poles, houses, hats and ocean-going canoes. Thuja plicata is a valuable timber tree because of its beautiful straight-grained, weatherproof wood. The similar-looking yellow cedar, Callitropsis nootkatensis, is probably second only to the red cedar in BC Coastal First Nations culture. The easily-carved wood is still especially prized for masks, poles and paddles. The two species are readily differentiated by their aromas: western red cedar by the sweet, pineapple-like smell of its handled foliage, and yellow cedar by the strong oregano- and sagebrush-tinged pong of both its wood and leaves. There are several specimens of yellow cedar in the Rainforest Garden. The most prominent is a lovely weeping selection (C. nootkatensis Pendula Group) just inside the entrance.  

Although not native to BC, Chamaecyparis lawsoniana (Lawson cypress), looks like it might be. This conifer, which has elegantly drooping branchlets of a finer texture than either western red or yellow cedar, is native to the mountains of northern California and southern Oregon. There are a few small specimens near the middle of the Pacific Slope Garden. This species is unfortunately highly susceptible to a root rotting disease both in cultivation and in the wild. Covering some of the same geographies, but extending further south is the California incense cedar, Calocedrus decurrens, an intensely aromatic species that was once harvested on a large scale for the manufacture of pencils. Our largest specimen, which exhibits the classic, narrow-upright habit of this snow-adapted species, sits above the Garry Oak Meadow Garden. Sequoia sempervirens, the coast redwood, needs no introduction for those lucky enough to have seen this lofty conifer in its habitat. For anyone else, my advice is to make plans to do that. Coast redwood is one of the natural wonders of the world—the tallest living organism, and definitely among the most awe-inspiring. Ours is about 10 years old, planted close to the fence in the middle of the Pacific Slope Garden. A mere pipsqueak at 3 m tall.   

Junipers are unusual in the cypress family in having separate male and female plants. They are also mostly notably aromatic and notoriously ill-adapted to Vancouver’s climate. Long-time Vancouver residents have seen junipers come and go as landscape shrubs, but the common juniper, Juniperus communis and its varieties are essentially bullet-proof shrubs. Juniperus communis var. communis is unfortunately also practically untouchable, with its sprawling habit and needle-sharp leaves. The cones on this plant (this specimen is a female) are copiously produced. If you are brave enough to handle them, you might detect the smell of gin, as juniper “berries” are commonly used to flavour that liquor. Across the path is the dwarf juniper, J. communis var. depressa (a male selection). Both are collections from southwestern BC made in the 1970s by the then curator of the BC Native Garden, Al Rose. Two European junipers, J. communis var. saxatilis (mountain juniper) and a horticultural selection, J. communis var. communis ‘Sentinel’ (a small, rocket-shaped shrub), are both located in the European section of the Alpine Garden. Rocky Mountain juniper, Juniperus scopulorum is well-known both for its bedraggled appearance (particularly when cultivated at the coast) and its strong off-putting odour. This is a species from BC’s Interior, but its range also extends across the Rockies and south to northern Mexico. Our largest plant is in the bed across the Service Road from the BC Rainforest Garden. In the North American section of the Alpine Garden close to the service road are two selections of Juniperus horizontalis, a prostrate-growing species that normally only thrives away from the coast. Their good health depends on full exposure to the sun and wind and superlative drainage. Similarly, two drought-adapted junipers from the southwestern states, Juniperus deppeana (alligator juniper—named for the scaly bark) and Juniperus occidentalis (western juniper) are recent additions to the Alpine Garden. Both are large, picturesque, long-lived trees where they are native.   

Wrapping up the Garden’s western North American cypresses are species in the genus Hesperocyparis. This relatively recently erected genus comprises North American plants that were traditionally included in Cupressus, which now includes only European, North African and Asian cypresses. We grow five species of Hesperocyparis, four of which (listed below) are native to California. The other, Hesperocyparis arizonica (Arizona cypress) is primarily native to Mexico, with small outliers in southern Arizona and New Mexico. We have a smallish plant (grown from wild-collected seed) in the Alpine Garden, and a much older, 7-m-tall tree, the cultivar ‘Silver Smoke’, near the Roseline Sturdy Amphitheatre. Our newest North American cypress addition is a trio of Hesperocyparis abramsiana (Santa Cruz cypress). These small plants join young Hesperocyparis macnabiana (Shasta cypress) and Hesperocyparis sargentii (Sargent cypress) seedlings in the Pacific Slope Garden. Both the Santa Cruz and Sargent cypresses are eventually good-sized trees, similar in scale with Arizona cypress. In contrast, Shasta cypress remains shrubby, but is known to be among the most resinous and aromatic of all cypresses. Hesperocyparis bakeri (Siskiyou cypress) are also planted in the Pacific Slope Garden in a range of sizes, though our largest—a 20-year-old specimen—is located in the Alpine Garden. Note also that the large hedge that surrounds the Service Yard is made from the exceptionally versatile ´x Hesperotropsis leylandii (Leyland cypress), which is a hybrid of two western North American cypresses: Hesperocyparis macrocarpa (Monterey cypress) and Callitropsis nootkatensis (yellow cedar). 

Submitted by: Douglas Justice, Associate Director, Horticulture and Collections