Monthly Garden Spotlight – December 2024

By RSBG Horticulturist and Assistant Curator Will Clausen

While December might be dark, often damp, and sometimes chilly, these characteristics make it perhaps the most atmospheric time of year in the garden. At its best, December is truly dramatic. Wisps of fog wending through the conifers, or entirely enveloping the garden creates an eerie scene with spiderwebs cloaking the rhododendrons revealed by the dew. The low angle of the sun can send beams of light shooting like spotlights through the branches to illuminate some unexpected delight deep in the garden.

The occasional snow blankets everything in white, coating the upper surface of the rhododendron leaves and highlighting the remarkable indumentum found on the lower surface of many of these plants. Torrential downpours of rain can sometime drown out the noise of the highway and remind us that this is in fact a happy place for rain-loving rhododendron. And even though it might be viewed as the month least likely to impress, December still offers up some botanical rewards to visitors.

Conservatory
As always, there is something blooming in the conservatory. And even if there wasn’t, it’s still a good spot to be when it’s cold and rainy. Near the bridge, Rhododendron macgregoriae is covered with medium-sized orange to yellow flowers. This species is relatively easy to grow and gives a reliable and superb floral show. Along the south wall near the back door, the long arching white flower so R. goodenoughii are more than its name suggests, while R. championae, though not in flower, still catches the eye with its dark magenta vegetative buds.

ADA Pathway
Exit the back door and follow the ADA path. Listen and look for birds that frequent the bigleaf maple. This is a great time of year to see kinglets, bushtits, wrens, chickadees and many others flitting together through the plants looking for spiders and other things to eat. On clear morning, low light illuminates the innumerable panicles of fruit hanging from the branches of Pterostyrax psilophyllus f. leveillei. Tucked back in a bed, Hydrangea macrophylla ‘Kardinal’ maintains its blue-purple bracts as the leaves yellow and fall away. Farther down, the R. degronianum ssp. yakushimanum flanking both sides of the trail near the Gazebo are all set with their flower buds for next May.

Alpine Rock Garden
Without the distraction of flowers to overwhelm the senses, December is a great time to take in the general form of plants. Coming down into the Alpine Rock Garden, take note of some fine, low mounds of several different rhododendron species from subsection Lapponica, like R. impeditum and R. fastigiatum. These plants have adapted well to life high on a mountain, huddled low and tight to limit damage from wind, cold, snow, and sun. Above them rise several interesting conifers. A mini grove of Serbian spruce (Picea omorika), a rare species with a really small range in the wild, showcases its lovely upswept branches. Just downhill, find a solitary weeping form of our native mountain hemlock (Tsuga mertensiana), a beautiful tree that is somewhat lost in the summer but stands out this time of year as the deciduous trees in the distance that serve as its backdrop have dropped their leaves.

Stumpery
The Stumpery is almost best in the winter as fronds wither away and the structure of the place is uncovered once again. Take a long look at the moss growing on some of the logs and stumps and you won’t regret having done it. Check for mushrooms still popping up here and there, slowly breaking down the wood. On the south end of the Stumpery, the bright yellow bark of Acer palmatum ‘Bihou’ glows among the dark foliage of the surrounding ferns and rhododendrons. R. griersonianum has set its long, tapered buds, while across the trail R. mallotum has set a number of its own round, felty flower buds ready for next spring.

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