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COSEWIC assessment and update status report on the Bluehearts in Canada

Biology

This species is hemiparasitic on the roots of a great variety of trees including Pinus strobus, Fraxinus pensylvanica, Populus deltoides, and Quercus alba (Musselman and Mann 1979; Baird and Riopel 1985; Krause and Weber 1990) and presumably other plants but can mature without parasitic attachment (Voss 1996). Musselman and Mann (1979) found that small trees could be severely damaged if large numbers of haustoria were present, and the effects of parasitism could be heightened during periods of stress such as drought conditions.

Buchnera americana has been described as a perennial plant (Brownell 1985, Ostlie 1990), however there is some question regarding whether it may survive primarily as an annual in Ontario and possibly other northern states. Alf Rider maintains that individual plants do not survive more than one year based on observations of transplants and potted plants. Permanently-marked monitoring quadrats have been established by the Indiana Dunes National Lakeshore and Indiana Division of Nature Preserves and by the Illinois Department of Conservation (Ostlie 1990).

The small seeds of B. americana require light for germination and can remain viable in the soil for 2.5-3 years based on limited testing (Ostlie 1990). Dr. J. Baskin suggests that this is a fairly good indication that the species may form seed banks in nature, although verification of this has not been attempted.

Pennell (1935) suggested that this species is butterfly pollinated, but also noted that self-pollination, based on colour and morphology, may be widespread. It is still not known whether or not this species is an obligate out-crosser, or whether self-fertilization is possible to set seed (Ostlie 1990).