THE little-leaf linden
Julietta Sorensen, Text-A-Tree Project Lead
2020-06-08
With spring well underway in what is now called Halifax, many of us find ourselves reacquainting with neighbourhood trees. As trees leaf out, we are met with a kaleidoscope of green-shades seemingly forgotten over the long winter. Amidst this cacophony, you may have noticed one tree along the streets of Halifax with the peculiar habit of sprouting little shoots around its base. This is the little-leaf linden (Tilia cordata Mill.), also known as the European linden (though this name can also apply to the naturally occurring hybrid Tilia x europaea). The shoots you see are referred to as basal or epicormic sprouting.
Street trees must be “trained” by pruners, meaning that through skillful removal of branches over several years, a tree will take on a shape where the trunk remains relatively bare and the branches and foliage are concentrated near the top. This is to provide visibility for both vehicles and pedestrians, and is one reason why trees of the same species may appear so different to us in urban areas as compared to rural. Despite this training, little-leafs have something of a reputation for relentlessly producing basal sprouts which require additional pruning (see photo). Basal sprouting is often a stress response shared by many tree species where the tree attempts to increase its energy capacity by putting out as many new leaves as possible. For lindens, however, this growth appears to be the norm rather than the exception and can serve as a useful indicator for fledgling tree-identifiers.
One benefit of little-leaf’s basal sprouting for the avid tree-admirer is that it grants you an opportunity to observe the buds up close. Over the winter these plump orange-red buds with their playful asymmetry are a welcome burst of colour. As a genus, lindens are most generally identified by their lopsided-heart shaped leaves, fragrant yellow flowers, and round nut-like fruits. These fruits were what caught my eye the first time I noticed a linden tree. They looked to me like a Dr. Seuss rendition of berries with the tiny twin globes. Even more bizarre, to me at least, was that the nuts joined an elongated stem that seemed pinned onto the bottom of an equally strange leaf. I later learned that this modified leaf structure is called a “bract”, and that this form is characteristic of lindens.
There is some debate as to how this common name originated. Some point to the German word “linde” meaning rope, and the way in which earlier peoples used the tree’s inner bark to weave strong cords. It may also refer to the Swedish scientist Linnaeus, who famously created the binomial nomenclature still used by scientists today. The source of the little-leafs name is much clearer. As the name suggests, little-leaf lindens tend to produce smaller leaves than other species in the genus Tilia. For example, while the basswood (Tilia americana L.) boasts 12-15 cm long leaves, those of the little-leaf are often half the size at around 8 cm.
Little-leaf lindens and their prolific planting contributed to Halifax’s fame as the city of trees, with many stately centurions gracing the HRM treescape. Little-leafs are now one of the dominant species throughout the Halifax peninsula with most of them already having reached maturity. While on average these trees grow to be about 15 to 20 m in height, they can reach as much as 35 m. Despite the abundance of little-leafs, it is unlikely that you will find a young tree, as the city has worked to provided greater balance to the urban forest by planting a wider variety of species. Instead, you may find 5 to 10-year-old American lindens (or basswoods).
Much of the zealous planting of European Linden is owed to its hardy nature and ability to withstand the stresses of urban life. Trees in urban areas undergo greater stresses than their cousins in rural regions, such as increased air pollution, temperature, soil compaction, and mechanical damage from weed whippers and snow ploughs. Lindens are long-lived and can easily reach 200 years of age. This, combined with their resilient nature and appealing symmetrical shape, make them excellent street trees. Beyond this, lindens produce bundles of fragrant flowers in mid-summer, providing an important resource for bees and other pollinators. While the sweet sticky sap is a hit in the insect world, it is not often appreciated by humans whose cars sit below!
Linden flowers have also played a role in European culture. Several species of linden exist across Europe (as well as in Asia and North America) and produce the aromatic clusters of yellow flowers. When steeped, these flowers produce a soothing tea, much like chamomile, which remains a popular folk remedy. While enjoying the tea, you might add a dollop of linden honey, produced by bees whose keepers have intentionally set their hives among these favoured trees. The leaves are also edible, with the fresh blades being collected for salads. I’ve tasted some local leaves myself, and while I wouldn’t say it was something to write home about, I do wonder if the growing movement of urban food security should not consider linden trees (and others) as possible sources of sustainable food.
With all this, its no wonder the little-leaf linden was so heavily favoured in the early days of planting Halifax’s streets. I’m thrilled that our city is now moving towards species diversification and especially the planting of species native to Eastern Canada. That said, I think the little-leaf has earned itself a special place in the heart of Halifax. It sure has in mine.
Few little-leaf lindens stand out as monumental trees in our streets, like elms, red oaks, and European beeches do. One on College St. near Carleton is an exception (see photo above). However, the Halifax peninsula boasts several iconic rows of little-leaf lindens – three of these are: (a) in the Holy Cross cemetery along South Park St. (pictured on the right); (b) along Sackville St. across from the Public Gardens (pictured in winter below); and (c) on the property of the main post office building on Almon St. (also pictured below).
