Starting point: Rosemont Boulevard entrance
We suggest that you start your tour from the northern tip of the Garden. This will bring you to the Arboretum straight away.
Note that there are no marked trails in the Arboretum. You will be walking on the grass and using the map to find your way around. If you are worried about getting lost, check the
Arboretum map or talk to the staff at the Tree House before you set out. They'll be happy to help.
Station 1: Larches
If you see some conifers covered with golden yellow needles across from the Tree House, don't worry. They're not sick. It's the natural colour
of larches (Larix spp.) in fall. In the conifer world, where evergreen foliage is the rule, larches are the exception.
Their needles turn colour in fall and drop off before winter arrives, just like the leaves on deciduous trees.
Yet keeping needles year-round would be a definite advantage in some regions with a short growing season and poor soil —
just the kind of regions larches prefer. It would help extend their growing season and require fewer nutrients
in the spring, since there would be no need for the foliage to grow back each year.
So does it make any sense at all for larches to shed their needles? Or has nature goofed?
No, it's not a mistake. In northern regions, the soil often remains frozen until very late in spring, whereas the air heats up sufficiently to cause water loss through the needles. Since the water in the ground is frozen and not accessible, larches shed their needles as a way of not becoming dehydrated in spring. What about other conifers? They close their stomata completely (stomata are tiny openings on the surface of the needles that allow the tree to breathe and transpire). In addition,
their needles are covered with a cuticle (a waxy layer that reduces water losses) thicker than that on larch needles.
Did you know...
The Arboretum is a very popular place with birds.
Most of the 183 species observed at the Garden visit the Arboretum. A network of birdfeeders has been put out to make
birdwatching easier in winter. |
Station 2: Maples
After walking past the pines and spruces, you'll come to a group of trees casting such dense shade that there isn't any grass under them. The maples (Acer spp.)!
Their delightful colours are due mainly to the gradual reduction in daylight. As winter approaches, deciduous trees form a membrane at the base of their leaf stalks, where the leaves will later drop off. Without their usual supply of minerals,
the leaves are unable to produce chlorophyll, and they lose their green colour.
The yellow and red pigments, masked by the chlorophyll all summer long, then become visible.
Maples' colour varies with the species: yellow for silver maples; orangeish-yellow to red for sugar maples; bright red for red maples, and so on.
Some are indigenous, some exotic, but all maples are excellent ornamental trees because of their stunning colours.
Silver maple (Acer saccharinum) was one of the first trees to be planted along city streets, in the late 19th century. Today, streets bordered by these giants are very popular with homeowners.
Starting in the 1920s,
Norway maples (Acer platanoides), which are highly tolerant of urban conditions, were also widely planted. In fact, they are the most common trees along Montréal streets today.
Finally, there are the infamous Manitoba maples (Acer negundo), those "undesirable" trees that manage to take root in cracks in sidewalks or laneways and grow to a surprising size.
Did you know...
The Arboretum covers a 40-ha area, equivalent to 59 football fields. |
Station 3: Oaks
Continuing south, you'll reach the huge collection of oaks (Quercus spp.). They were planted well apart from one another to give them all the space they need to spread their broad leafy crowns.
Some specimens of English oak (Quercus robur) have massive branches that stretch outward for several metres!
It's easy to understand why oaks are associated with strength, hardiness and longevity. In fact, the Latin name of the genus,
Quercus, comes from the Celtic words quer (fine) and cuez (tree).
In this collection of "fine trees", the red oaks (Quercus rubra) stand out because of their magnificent bronze-red fall foliage.
A bit later in the season, it is the upright , narrow English oaks (Quercus robur 'Fastigiata')
that steal the show, with their marcescent leaves — intriguing, to say the least.
While the great majority of our deciduous trees lose their leaves in late fall, those of this upright English oak remain on the
branches all winter long and don't drop off until the spring. That is what marcescent means.
At one time there were many red, white (Quercus alba) and bur (Quercus macrocarpa) oaks in Southern Quebec.
The popularity of oak for shipbuilding, cabinet-, carriage- and barrel-making and as firewood quickly reduced their numbers,
however. Even today, oak is very popular because it is hard, heavy and strong, with a tight, durable grain.
Station 4: Mountain ashes
After the magnificent oaks come the flamboyant mountain ashes (Sorbus spp.). Their clusters of vivid
orangeish-red fruit make them exceptional ornamental trees, and plentiful sources of food for birds!
Their berries have long been used to make jellies. They are very bitter, but become sweeter after the first cold fall nights, and remain on the tree all winter long.
The collection includes many species and cultivars that produce similar fruit, despite their differences.
Some European species have simple leaves, unlike North American mountain ashes, which have compound leaves.
Although they are quite cold tolerant, mountain ashes are not particularly hardy trees. They are subject to many diseases,
the most common being
bacterial blight, which propagates rapidly and causes the leaves to wilt.
You can probably see evidence of it on a number of specimens. This is why we suggest that you not plant mountain
ashes near your fruit trees, for they can become sources of infestation.
Station 5: Walnuts
When you see squirrels busy gathering what look like greenish-yellow golf balls, you'll know you've reached the walnuts!
These trees grow in rich, well-drained soil, and need plenty of sun. They secrete a toxin called juglone from their roots, which inhibits the growth of many competitors.
In Canada, black walnuts (Juglans nigra) occur naturally only in southern Ontario. However, they are found throughout southern Quebec, where they are planted as ornamentals and in
test plantations for producing noble wood.
English walnuts (Juglans regia), originally from Europe, produce the famous nuts and a lighter wood than black walnuts.
Butternuts (Juglans cinerea), the only walnuts native to Quebec, also have
high-quality wood and nuts, but are less widely used than black and English walnuts. They are hardier, however.
Butternut trees in Canada and the United States are threatened by butternut canker, an infection caused by a fungus (Sirococcus clavigignenti-juglandacearum)
and that can seriously damage and even kill them.
Station 6: Ginkgos
You'll feel as though you've stepped back into ancient China as you stroll through the splendid collection of ginkgos, with their shiny golden foliage.
The Ginkgo biloba is a real living fossil, a tree that co-existed with the dinosaurs 150 million years ago.
It outlived their extinction and the ice ages, sheltered in a natural refuge in the mountains of eastern China. Today it is the only member of the Ginkgoaceae family. A botanist named Kaempfer first
observed it in Japan and introduced it to the West in 1690. It is also known as the maidenhair tree.
Today ginkgos are very popular ornamental trees all around the world. Highly resistant to pollution, insect pests and diseases, Gingko biloba is an ideal tree for city settings. Avoid planting female specimens, though, for their fruit gives off a very unpleasant odour after it drops. You'll see that even the hungriest squirrels avoid the fruit of the only female tree at the Arboretum.
All the other ginkgos in the collection are males, although the sex of three of the trees is as yet unknown.
Final station: The Tree House
Are you still puzzling over some question that occurred to you during your stroll?
One of the Tree House staff members is sure to have the answer. Take the opportunity to
visit our two magnificent exhibitions. At the Heart of the Tree will introduce you to every dimension of trees,
while the temporary exhibition is bound to interest and intrigue you. Enjoy your visit!
This article, by Étienne Laliberté and Guylain Boudreau, originally appeared in Quatre-Temps
(Vol. 27, No. 3, September 2003). At the time they wrote the article, the authors were activity staff members at the Tree House in the Montréal Botanical Garden. |
