island of trees: Hackberry: the tree that migrates

Illustrations coming

You know this tree from its nobbly pale park, which looks possibly diseased, perhaps with a tree’s form of leprosy. It’s simple, alternate leaves are a bright, pale green in spring. At this time of year, the leaves are paling, some arriving at a pale creamy yellow. In the forest of Île Ste- Hélène, the biggest hackberry grove I know, they are resplendent in contrast with the oranges of the sugar maples and the bright, shiny yellows of the red ash.

Until discovering this grove I knew hackberry only as a street and park tree. Tough to salt and compacted soil, the tree does well in the city as is clear by the row growing against the massive St-Louis –de-France church on Berry Street, as one approaches Roy Street. I did wonder, however, about the 1.5 metre  in diametre giant in the Mount Royal Cemetery. Until this tree lost a major bit of its girth to the 1998 Ice Storm, is was considered the biggest hackberry in Quebec. (You’ll find it named and numbered in the Cemetery’s self-guided tree walk). Most likely, therefore, it is older than the cemetery, which opened in 1852 and is a vestige of the original forest, composed of red oak, white pine, sugar maple, black cherry, beech, elm and white ash.

The island of Montreal is the most northerly extreme for this Carolinian tree that flourishes in the Pelee Islands on the southwest end of Lake Erie and at other points south. Some believe, in fact that the tree has only been in the Windsor area since the turn of the 20^th century and has been migrating northeast along the Great Lakes-St Lawrence Valley ever since.

That doesn’t however, explain the old tree at the Cemetery, unless it indicates another migration route for waterfowl and wild turkeys, two of the trees greatest fans. You see, the hackberrry, whose original name was the hagberry, an old English name for the sweet European cherry tree, Prunus avium, produces a sweet, dark blue berry every fall and migrating birds regale in the fleshy fruit, then fly off and deposit the seed at their next island or shoreline stop. This is why we find such concentrations of the tree on Île Ste-Hélène, Île aux hérons and Île Dorval. And I wonder if on Mount Royal, when Beaver Lake was a true pond and Le ruisseau de la montagne flowed freely, if the mountain too was not a favourite spot for both migratory birds and hackberry trees.

I should make clear that the hackberry is not a cherry tree, but stands in a family of its own, the Celtis family. Celtis occidentalis is the name of our native species while there are at least two other more southerly North American species and several Eurasian ones. Until recently, the tree was considered a member of the elm family, mostly due to the asymmetry and toothiness of the leaf, and the tree’s overall shape. The flower and fruit, however, bear no similarity to the elm, which produces its flower and samara type (winged) seed early in spring, often before the leaves emerge. The hackberry, on the other hand, produces both its male (pollen) and female (seed-producing) flowers at the same time as the leaves are emerging in mid-May. The fruit ripens only in the fall. If you look up, there’s a good chance you’ll see some of the dark blue berries still hanging from their single stems.

While the tree many not be an elm, it has been widely planted to replace the great old trees, due to its resistance to salt, drought and compacted soil, as well as its lovely shape and colour.

From my point of view, the bark is the most alluring characteristic of this unusual tree. Always a pale greenish grey, sometimes bumpy, sometimes showing the lines of a mysterious contour map, sometimes –though rarely –smooth, the bark stands out amidst its darker-barked accomplices. The bark is also a handy shelter for migrating monarch butterflies while they collect at Point Pelee, waiting for the perfect updrafts to moment to cross Lake Erie. After a month of so of flying and coasting, our royal insect settles in its winter throne in the Oyamel Pine tree, high in the Mexican mountains.