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COSEWIC Assessment and Status Report on the Eastern Flowering Dogwood in Canada

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COSEWIC
Executive Summary

Eastern Flowering Dogwood
Cornus Florida

Species Information

Eastern flowering dogwood (Cornus florida) is a small tree of the forest understory or edge. It has branches in whorls from the main trunk, giving a tiered appearance. Leaves are simple, opposite and deciduous. Flowers are in terminal clusters with four conspicuous white floral bracts. Fruit occurs in tight clusters; scarlet, shiny, one-seeded, ovoid and fleshy. It is similar to Cornus alternifolia, but the latter has alternate leaves and branching, lacks the floral bracts and fruit are dark green to blue in an open cluster.

 

Distribution

It is a species of eastern North America, ranging in the north from southern Michigan, southern Ontario and southern Maine, south to eastern Texas to northern Florida; two disjunct populations occur in the mountains of eastern Mexico. Only a small percentage of its range is in Canada.

 

Habitat

Cornus florida typically occurs as an understory or edge tree of open dry to slightly moist deciduous or mixed forests, on sand to sandy loam or occasionally on clay loam soils, typically in mid-age to mature forests.

 

Biology

This species is a long-lived, slow growing woody perennial. Flowers are perfect (having both male and female parts) and occur in mid-spring as the leaves are beginning to open. Individuals are pollinated by insects; cross-pollination produces better seed set. The mature red fruits are dispersed by numerous birds and a few mammals. Germination and seedling establishment occur in forest shade but intermediate light levels promote growth.

 

Population Sizes and Trends

Populations range from individual trees, to many that have one to a few dozen trees, to one with over 100. Since the arrival of dogwood anthracnose (a leaf disease causing mortality) in the mid-1990s many populations are in a steep decline, an average of 7-8% per year.

 

Limiting Factors and Threats

The greatest threat is the dogwood anthracnose disease that has decimated many populations and only a few seem to have so far avoided its impact. In addition to high mortality, the remaining individuals have reduced flowering and fruiting.

 

Special Significance of the Species

Cornus florida is a conspicuous understory tree in southern Ontario forests, providing nutrition for pollinating insects in the spring and frugivorous (fruit-eating) forest birds in late summer. It is also an important small, ornamental landscape tree. First Nations made use of Cornus florida for various medicinal treatments. This species, plus its western counterpart Cornus nuttallii, are threatened by dogwood anthracnose throughout their ranges. 

 

Existing Protection

Several jurisdictions are reviewing the status of this species due to its drastic decline after the arrival of dogwood anthracnose. Three states have it listed as S1 (critically imperiled); Ontario currently lists it as S2 (imperiled).