Far From Home: Species in Danger|
BY NATURE CANADA SPRING 1993IN CANADA, THE WHITE PRAIRIE GENTIAN IS FOUND ON A SINGLE ISLAND IN SOUTHERN ONTARIO...one might expect a species named the white prairie gentian to be found in the wide open spaces of Canada's Prairie provinces. Instead, this plant's only known home in Canada is on Walpole Island in the delta of the St. Clair River near Sarnia.
The white prairie gentian is considered a relic in our country. Its presence is left over from a period about 3000 years ago when a warmer, drier climate permitted prairie conditions to extend into southern Ontario. Today, the main range of the species is centered in the plains of the Midwestern states.
In the 1800's the white prairie gentian was discovered at two Ontario sites hundreds of kilometers apart. Both have long since been lost to development and, for many years, the species was thought to have been extirpated from Canada. Then, in 1984, it was discovered on Walpole Island.
The white prairie gentian is found in association with limestone or on soils otherwise rich in calcium. It requires a well-drained site and is intolerant of shade. On Walpole Island most of the 20 or so presently known plants grow on a low sandy ridge under an open canopy of widely spaced oaks and hickories. This sub-climax community is maintained by a regime of fire management, a traditional practice of the Walpole Island First Nation.
Belonging to the closed gentian group, the white prairie gentian produces flowers which open only slightly. Plants are sturdy, with a number of stems emerging from a perennial rootstock. They may reach heights of up to 90 centimeters, yet are notoriously hard to spot growing in the wild. Torpedo-shaped clusters form compact cluster, usually at the top of stems. The pleated petals vary in color from greenish-white to yellowish-white. They appear from mid-August to late September.
Pollination is carried out by bumble bees, insects with enough strength to open the flowers. Seed capsules mature in October, splitting in two to release hundreds of tiny winged seeds which are dispersed by the wind.
The white prairie gentian is closely related to the more common closed gentian. Although the former flowers earlier and prefers higher sites, hybrids have been found where the two species grow in close proximity on Walpole Island.
The unique habitats and plant communities of Walpole Island support a lengthy list of rare plant species, many of them of prairie affinity. The local First Nation Council is aware of this valuable natural heritage and hopes to preserve and appropriately manage sensitive areas of the island.
Unfortunately, in recent years, an increasing amount of higher ground on the island is being used for other purposes: home construction, light industry, sand quarrying, and agriculture. With more development, pressure is growing for fire control measures in order to protect private property.
Periodic burning, however, is critical to maintaining the open conditions that keep the white prairie gentian and other prairie-related species from being shaded out. Fires must also be precisely timed; if burns occur too late in spring the gentians will be destroyed.
Ongoing management practices in the island's marshes are of consequence as well. Raising the water level in adjacent wetlands would favor the closed gentian and increase the possibly of competition and hybridization.
In 1991, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assigned endangered status to the white prairie gentian. The designation recognized the species 'very low numbers; its history of extirpation at various sites; and the complexity of the management and protection strategies necessary to ensure its survival in this country.'