The japanese tree lilac
Julietta Sorensen Kass, Halifax Tree Project
2020-07-27
The botanists and foresters among you may know this tree by its Latin name, Syringa reticulata (Blume) H. Hara. It is a member of the olive family. Some refer to it by the shorthand “syringa”, and others by the common name “Japanese tree lilac”. Whatever you call it, if you do at all, Halifax locals are likely to recognize the distinct scent of its flowers. As with the famously scented lavender plant, lilacs produce an aroma that is uniquely their own. For flat-landers like myself, the fragrance is a nostalgic reminder of spring time, as the lilac bush is favoured around the towns and cities of southern Alberta. However, unlike the more common shrubby variants of lilac (e.g. Syringa vulgaris L., or the common lilac), syringa is the only one to grow in the form and size of a tree.
Syringas are relatively small trees, growing to about 9 m in height (see the photo, left, of the large one in the Halifax Public Gardens). In the city you’ll often see them pared down a single trunk, though they can also grow in multi-stemmed clusters. The leaves are oval with long pointed tips, with gentle waves along the margins. I’ve often found myself grinning in the early spring when the street trees of downtown Halifax just begin to leaf out. It seems to me that the leaves of the Japanese tree lilac look a little too big for young trees from whose twiggy branches they sprout. Where I lived, there were several newly planted syringas with shiny slender trunks and floppy leaves which reminded me of puppy-dog ears. The rich green leaves are slightly fuzzy underneath, which adds to the comical comparison. Though their life span is somewhat brief at around 40 to 50 years, they make up for it with moderately fast growth and an impressive degree of resilience and adaptability. Syringas in the streets of Halifax are mostly small young ones planted since the HRM Urban Forest Master Plan came into effect in 2012.
The creamy white clusters of sweet-smelling flowers are how most people recognize the syringa. Less often appreciated, though equally lovely in my mind, is the shimmering bark of young stems and branches. Like many, I found myself pacing tracks around the neighbourhood to keep from going stir crazy during the early stages of Nova Scotia’s Covid-19 shutdown. Not for the first time, I was struck by the metallic sheen of the young papery bark. The texture of the bark changes with age, becoming rougher and losing that shimmer. When it is young though, the delicate bark can be peeled back like a thin film of copper. If, like me, you’ve ever found yourself gleefully inspecting the bark of one such newly befriended tree, then you might have wondered what those spots were. The flattened ovals running horizontally across the tree’s surface are called lenticels, and are seen in other common street trees such as ornamental cherries and various species of birch. You might be surprised to learn that all woody stems and roots have lenticels, though they are usually much less visible. In school you likely learned that plants exchange gases with their surroundings through tiny flexible holes in their leaves called stomata. Lenticels are essentially the stomata equivalent for gas exchange in woody cells.
Another joy of the syringa comes from its ability to support pollinators. In fact, the Japanese tree lilac has been listed as one of the top tree species to plant in support of backyard pollinators (Bowerandbranch.com). While the scented flowers can cause difficulties for humans suffering from allergies, they are valuable resources for species of insects whose ecosystem services form the basis of our food systems. The memorable scent and benefit to pollinators brings up another interesting discussion point. Within urban forest discourse, it is common to view trees in terms of their value in carbon sequestration and shade production. As a small, short-lived tree, the syringa does not fare well in either of these categories. Yet many of us love this tree deeply. Though we may not always be aware of it, we value trees for far more than just what meets the eye or nose. Managing for a wide range of values is important for ensuring that our urban forest meets the needs of all the city’s inhabitants, both human and beyond-human.
As the name suggests, the Japanese tree lilac is native to Japan, but also to northern China, Korea, and southeastern Russia. It was recently pointed out to me that no street tree has ever arrived there by accident, and that even the weeds in the city are there as a result of their relationships with humans. Though it sounds like a statement which should not need saying, it got me thinking. The humans of what is now called Halifax brought with them their customs, values, and – sometimes – trees. To me this means that as I walk down the street and smile thinking about the floppy-eared syringa, I am walking through a socio-ecological tapestry made all the more vibrant by diversity. In a time when our world seems entirely upended, it’s these connections that keep me grounded, and I find myself all the more grateful for our urban forest.