Carolinian Forest Garden
In Canada, the diverse eastern North American deciduous hardwood forest that extends from the Gulf Coast of the United States into southern Ontario is known as the Carolinian Forest, after the region where the considerable biodiversity of this rich assemblage reaches its peak. Despite the distance and differences in climate, the vast majority of species from throughout this region can be grown in the Vancouver area. A large number of eastern North American plants have their closest relatives in east Asia, while others have family links in both Asia and western North America. The study of such related, but geographically separated organisms is called biogeography and because all of these regions are represented in the Botanical Garden, biogeography is a common theme in education, conservation and biodiversity research in the garden.
The Carolinian Forest Garden is a new feature in the Botanical Garden, consisting of twelve individual groves, each named for an early North American plant explorer. The groves are planted with hundreds of different tree and shrub species and pathways are easily accessible to all visitors. The Carolinian Forest region is also noted for the diversity of its herbaceous flora, and eventually, as the arboretum grows and the tree canopy closes, herbaceous plants will be added. Currently, the groves are mulched heavily to reduce maintenance.
One of the most distinctive features of the plants of Carolinian Forest is autumn leaf colour. Maples, oaks, sumacs, tupelos, sweetgums and sourwoods are all noted for their spectacular effect. Colourful fruits, too, are a common feature in the arboretum. Roses, mountain ash and elderberries not only contribute colour, but considerable birdlife, as well.
Some of the better-known examples of East Asian-Eastern North American biogeographic disjunctions are illustrated by collections in the Carolinian Forest Garden and David C. Lam Asian Garden. There are examples of magnolia, Acer (maple), rhododendron, Calycanthus (sweet shrub), Sorbus (mountain ash), Nyssa (tupelo), Cornus (dogwood) and many others here. One of the best studied species pairs is Liriodendron tulipifera (American tulip poplar) and Liriodendron chinense (Chinese tulip poplar). Molecular analysis and carbon dating of fossils shows these two species are extremely closely related—virtually identical, genetically—despite being separated for the last 60 million years.
The late Gerald Straley (1945-1997), former curator of collections and research scientist at the Botanical Garden, and a native of Virginia, had always advocated for a collection of eastern North American hardwoods in the Garden. He argued that there were few examples of this rich and biologically important floristic assemblage displayed locally. In 2006, planting was begun on the vacant land in the southwest corner of the North Garden. Plants were acquired from a variety of sources; the majority of accessions are of known provenance and derived from collectors, botanical gardens and government sources in eastern North America. Echoing the plant exploration theme of trail names in the Asian Garden, plantings in the Carolinian Forest reflect the historical significance of early plant collecting in eastern North America. Individual groves are named for plant explorers, each with signature species that illustrate that history. For example, Franklinia alatamaha, which is extinct in the wild, is one of the featured species in the Bartram Grove. William Bartram (1739-1823) collected seed of this outstanding ornamental in the wild, but was probably the last to do so, as it was never found again.
In winter, the blue-green, chalky white-striped stems of the moosewood or striped maple (Acer pensylvanicum) stands out. A strikingly beautiful species, its closest relative is the nearly identical Mandshurian maple (Acer tegmentosum) from eastern China, which can be seen in the Asian Garden.