World of Trees
About 100 million years ago as flowering plants were establishing, North America was still connected to Europe and Asia, and there was no polar ice cap. Tropical vegetation covered the present-day grounds of The Arboretum, and a single great forest stretched, uninterrupted across the continent. Continent drift, evolution, and time has resulted in the variation you see today.
The World of Trees Collection is a place where you can discover some of the amazing similarities and differences associated with temperate woody plants of the northern hemisphere. Some families such as the maple family are relatively similar in general appearance, while others such as the rose family are very diverse. More that 400 species of trees and shrubs representing 158 genera and 67 different plant families are established on this 5-hectare site. They are arranged in family groups situated along the 0.7km (0.5 mile) World of Trees trail. Many of Ontario's native woody plants (including several rare species) are represented here along with their relatives from Europe or Asia. Each plant's name and its family name can be found on a black metal label at the base of the plant.
One of the major concerns of global conservation today is the increasing loss of species (and thus biodiversity), those vital components in our support biosphere that keep the system running smoothly. The World of Trees Collection offers a sampling of diversity found in the world's temperate regions. Some representatives of very ancient floras still persist, for example, the Ginkgo tree's ancestors predate the dinosaurs! Among it's "naked-seeded" (gymnosperm) relatives are several conifers that also occur far back in the fossil record; the shrubby Ephedra is an odd member of this group. Flowering plants which have seeds enclosed in ovaries (angiosperm) are more modern, and dominant in most floras. They are divided into 2 groups; those with two seed leaves (dicot; e.g. willows and maples) and those with one (monocot; e.g. grasses and palms). In the temperate region, most of our woody plants are the former dicot group as there are only a few woody monocots in colder climates such as greenbriers and a few hardy bamboos.
Plants have developed a very wide array of reproductive systems and strategies. Many mechanisms function to avoid or reduce inbreeding. These range from having distinct male and female individuals (e.g. willows and bittersweet) to completely circumventing normal reproductive means and producing seeds without pollination, and thus identical to their mother (e.g. several trees in the rose family). Other adaptations enhance effective pollination and seed dispersal.
Think about the perils of being a tree! With a massive trunk held high in the air, trees are vulnerable to attack and upset. Despite this, they are one of the dominant growth forms in most regions, and therefore the first to intercept the sun's energy. By examining how different trees grow, one gains a beginning of an understanding of the evolutionary struggle to reach great heights. Many trees have distinctly different terminal and side branches, in others there is essentially no difference. Some trees have no "terminal" branches at all, but nevertheless manage to be forest canopy trees (e.g. elms and hemlocks). Consider how these different growth forms suit different trees in nature.
Woody plants have provided humans with numerous resources throughout history. While wood and fibre for building, transportation, tools, and fuel come first to mind, there are a number of other products as well. Many woody plants produce nuts and fruit, or nectar for honey. The vast storehouse of biochemical compounds found in different species has been used for medicines by cultures worldwide. The cultivation of plants for created landscapes can be traced back to early recorded history. Garden design has functioned to moderate severe environments from extremes of temperature, wind, noise, and glare, as well as to create visual beauty.
How have woody plants been incorporated into your own garden and neighbourhood?