December 2023 in the Garden

Rhododendron ‘Rosevallon’

Following on from our plunge into evergreen viburnums in November, I thought it appropriate to continue delving into UBC Botanical Garden’s vast collection of broad-leaved evergreens. The rhododendron family, Ericaceae, is a good place to start for December. Rhododendron is a veritable treasure-trove of assets in the Garden, and when not flowering, provides a verdant backdrop for other plants in the David C. Lam Asian Garden. A number are worth noting for their foliage alone. Rhododendron rex (on Delavay Trail, just south of the Moon Gate), for example, stands out for its large leaves and general magnificence (rex = the king). It is a shrub that clearly has a future as a tree.

Smaller foliage can be impressive, too. The dull, dusty-blue-green, aromatic leaves of Rhododendron cinnabarinum subsp. xanthocodon Concatenans Group (on Kingdon Ward Way) are also compelling (and even more striking with their hanging bells of Dijon mustard-coloured flowers in May). Of similar stature, Rhododendron wiltonii, like the aforementioned R. rex, has a thin woolly indumentum on the lower surface of its leaves. Above is a glossy surface impressed with reticulated veins (a single specimen on Siebold Trail north of Rock Trail). Subtle, but very handsome. Nearby is Rhododendron ‘Rosevallon’ which would be barely worth a mention at this time of year, except for its startling iridescent purple leaf backs.

There are plenty other rhododendrons (about 450 more) to see in the Garden, but there are also huge numbers of rhododendron relatives. Ericaceous plants are well adapted to our well-drained, acidic soils and moderate maritime climate. Arguably our finest native ericad is salal, Gaultheria shallon, a tough evergreen shrub that ranges from Alaska south to California. There are good colonies throughout the Asian Garden, including along Upper Asian Way between the Service Road and Maries Trail (still in flower in November), and the BC Rainforest Garden. The considerably more diminutive Gaultheria procumbens (wintergreen), a low (ground-level) evergreen perennial that hails from eastern North America, is equally attractive. A sizeable mat is located in the Carolinian Forest Garden at the east end of the Fraser Bed. Technically classified as a sub-shrub—the non-woody above-ground stems arise from a permanent network of woody underground stems—the plant is most famous for the smell of wintergreen (methyl salicylate) that emanates from its leaves and fruits. Another attractive and even smaller rhizomatous gaultheria, Ito’s wintergreen, Gaultheria borneensis, has tiny leaves and prolific clusters of tiny, pure white berries. There is an ever-widening patch under the uppermost Pinus parviflora Glauca Group in the Asian section of the Alpine Garden. Some berries will still be visible in December, poking out through the mat of pine needles.

The manzanitas are also ericads, though more closely related to blueberries than to rhododendrons, and shade intolerant in Vancouver’s dull climate. When well-sited, however, they are very early to flower in the spring, and their flower buds are an ornamental feature throughout the winter. Visitors are greeted by a couple of handsome specimens of our native Arctostaphylos columbiana (hairy manzanita), near the tunnel entrance in the Garry Oak Meadow, then again along the path at the top of the hill. To be accurate, hairy manzanita is only native to steep, rocky, south-facing slopes on southern Vancouver Island, the southern Gulf Islands and the Sunshine Coast (and south to California), and not to anywhere near Vancouver. The common manzanita, Arctostaphylos manzanita (west side of the Trough Courtyard) is a native of northwestern California and arguably one of the most beautiful species in this genus of exceptionally attractive shrubs. It is also one of the easiest manzanitas to cultivate locally (definitely more adaptable than Arctostaphylos columbiana). Best seen with early morning or late afternoon sun on its papery, peeling mahogany-brown stems, the species is worth seeing even when atmospheric conditions are less agreeable. An older specimen, now long dead, once graced the east end of the North American section of the E. H. Lohbrunner Alpine Garden. Before it died, it spawned two seedlings—hybrids, we presume, with a nearby Arctostaphylos uva-ursi (kinnikinnick), now also gone—and these are still present where they first arose. We call them Arctostaphylos Hybrid A and Arctostaphylos Hybrid B (stirringly beautiful names, I know). The two are intermediate in foliage and form between the presumed parents. Both are spreading; one (Hybrid B) has smaller leaves and is less strongly upright than the other.

Vaccinium is another important ericaceous genus. Unlike Arctostaphylos and Gaultheria, a good number are deciduous (the common highbush blueberry and red huckleberry, for instance). The evergreen vacciniums are invariably handsome shrubs. Two in particular deserve mention. Vaccinium moupinense is a low mounding shrub with small, oblong, convex leaves. A high-mountain species from central and southwestern China, it generally adopts an epiphytic lifestyle (i.e., it favours growing in the duff built up on tree branches, logs, stumps, etc.). Despite its usual modus operandi, our best plant grows in the ground, directly below the superb Acer griseum (paperbark maple) in the upper Asian section of the Alpine Garden. The other notable species is our native Vaccinium ovatum, which is known as the evergreen huckleberry or evergreen blueberry, a shrub native along BC’s outer coast, south to California. Our largest are specimens of the cultivar ‘Thunderbird’, a UBC Botanical Garden selection that originated from a plant found outside of Tofino on Vancouver Island. They are located a few steps inside the entrance to the BC Rainforest Garden. Besides its bright coppery orange to shrimp-pink new growth and red-burnished winter colour, ‘Thunderbird’ boasts self-fertile flowers (i.e., it produces plenty of fruit without cross pollination) and delicious blue-bloomed berries.

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