Common hoptree (Ptelea trifoliata) COSEWIC assessment and status report: chapter 6

Biology

General

Common hoptree is late to leaf out, with flowers appearing at the end of the new growth in late spring, typically during the first two weeks of June in its Ontario range. Fruit matures late in the summer, is wind dispersed during late fall to winter, and seedlings develop after winter stratification which breaks dormancy.

Seedlings develop in full sun to partial shade. Increasing shade appears to suppress flowering and in areas where a full forest canopy has developed this species rarely persists. It appears to be short lived, perhaps in part to its occurrence mostly on dynamic sites where specimens rarely reach a large size.

Reproduction

Flowers were observed with a large variety of insect visitors, primarily bees, flies and beetles. The species is dioecious with ratios skewed towards males (Ambrose et al., 1985). No evidence of clonal reproduction has been observed. The germination ecology has been examined by McLeod and Murphy (1977).

Survival

Individual plants are likely short-lived, due to their occurrence in dynamic habitats where vegetation is periodically up-rooted by winter storms and ice, or being shaded out in forests with closing canopies. However, seedlings readily establish in the open habitats, replacing lost vegetation.

Dispersal

Seeds are dispersed within the dry winged indehiscent fruit during the fall and winter. Individual fruit typically contain two seeds. Thus an individual dispersal event to a distant site could produce a male and female seedling, allowing for continued reproduction.

Nutrition and Interspecific Interactions

Robust populations occur on sites of beach sand, likely of low nutrient levels, with nutrient inputs likely limited to wind blown debris and lake water. Pollinating insects are important for good seed development (Ambrose et al., 1985). 

A twig-boring beetle (family Scolytidae, determined by Professor Steve Marshall, University of Guelph; awaiting species determination from a specialist in Ottawa) was observed on several of the populations, causing losses of major parts of affected trees, including loss of flowering. The larvae of the Giant Swallowtail butterfly (Papilio cresphontes) feed on this species but do not cause major damage.

Adaptability

Most populations are on beach sand, including the inland population at Thamesville, but some populations also occur on other soils, such as on the Pelee Island alvars and along drainage ditches where soils are heavy lake bottom clays and clay-loams.

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