By Nigel Finney, Natural Heritage Ecologist | Conservation Halton
Eastern Flowering Dogwood (Cornus florida) is more than an ornamental plant; it’s an endangered tree, native to the deciduous and mixed forests of Halton and the rest of the Carolinian Zone in Ontario. The bright red fruit it produces are important food sources for over 50 species of birds and small mammals.
These trees, which reach three to ten metres in height, are threatened by the Dogwood anthracnose fungus. The fungus first attacks the leaves and then spreads through the twigs and trunk, causing the tree to die.
Anthracnose fungus was first confirmed in Canada in 1998 (the United States confirmed it in 1978), and while its origins are unknown, it was likely introduced to North America, meaning it is not a native species. The fungus is dispersed by rain, insects, and likely, by birds as well. It kills plants of all sizes and infection causes a high degree of mortality, 25 to 75 percent.
In 2002, the Ontario Ministry of Natural Resources (MNR) first noted concerns about the widespread decline of Eastern Flowering Dogwood in Ontario. The species was federally listed as endangered in 2007 and provincially listed as endangered in 2009. Through the provincial Endangered Species Act, an Ontario Recovery Strategy was finalized in fall of 2010.
In 2010, Conservation Halton, in partnership with the Ministry of Natural Resource, through the MNR Species at Risk Stewardship Fund, conducted field surveys to determine the locations and health of Eastern Flowering Dogwoods in suitable habitats in Halton.
Over 104 trees were documented in Halton with the majority observed along the south-facing slopes below the Niagara Escarpment, within the Cootes to Escarpment study area. In Halton, this species is typically found in Dry White Oak and Red Oak Woodlands as well as Dry-Fresh Oak and Sugar Maple Forests. The average diameter of the trees documented was 4.5 cm, with the largest documented at 12.5 cm.
The population of this species in Halton is unique as it contains the most northerly, naturally occurring, Eastern Flowering Dogwoods throughout its range in Canada. The most northern location of this species is found below the escarpment around the Mount Nemo area.
Updated surveys across Halton showed that Grindstone Creek Valley has the highest number of Eastern Flowering Dogwoods in our watershed. Conservation Halton and the Bruce Trail Conservancy secured this significant site in partnership with Ontario Heritage Trust (who own the land), thus benefitting the species through the longterm land protection.
The surveys took preliminary measures to identify populations and monitor the health and threats as outlined in the recovery strategy. Preliminary results showed that more than 15 per cent of the trees showed symptoms of a high likelihood of infection from the fungus, and almost 50 per cent of them showed reasonable health levels.
Of all the Eastern Flowering Dogwoods in our area, just over a third of them are protected through public land ownership (Conservation Halton, Ontario Parks, Bruce Trail Conservancy and the City of Burlington), the remainder are located in private woodlots.
Conservation Halton ecologists and the MNR are looking forward to the protection and recovery Eastern Flowering Dogwood in Halton. This will be done by conserving existing populations, actively monitoring its rate of decline, assessing habitat health, and where possible, restoring populations through plantings.
About Species at Risk
A “species at risk” is any naturally occurring plant or animal in danger of extinction or of disappearing from the province. To learn more about species at risk in Ontario, visit the Ministry of Natural Resources website – www.mnr.gov.on.ca. For more information on the natural environment in our watershed go to www.conservationhalton.ca. If you know of any Eastern Flowering Dogwoods or other species at risk, let us know.