Bashful bulrush (Trichophorum planifolium) COSEWIC status report: chapter 2

Description

Bashful Bulrush (Trichophorum planifolium = Scirpus verecundus) is a member of the sedge family. It forms small clumps of short, erect, grass-like leaves. In the spring, each clump produces from several to several dozen delicate flowering stalks (culms) that are triangular in cross-section and generally only 10-20 cm high. A small solitary spike develops at the end of each culm. The spike consists of several petal-less flowers, each of which is partly enclosed by an awn-tipped bract. Bashful Bulrush generally occurs as loosely-associated patches of from a few to several hundred clumps. Later in the season, the leaves and culms tend to fall over and become matted on the forest floor.

Distribution

The species has a rather limited range in northeastern North America. It occurs in the United States from southern Maine south to northern Virginia and west to Indiana and eastern Missouri. Its only Canadian occurrence is in southern Ontario in the eastern region of Metropolitan Toronto and at the Hamilton Botanical Gardens.

Habitat

In Canada, Bashful Bulrush is found in open-canopied forest with little shrub cover and excellent drainage. It is found on semi-open south- or west-facing slopes in deciduous and mixed woods.

General Biology

It is a perennial species and, like other members of the sedge family, is wind-pollinated. Its Ontario sites are confined to the western Lake Ontario shoreline that has one of the warmest climates and longest growing seasons in the province.

Population Sizes and Trends

In 1986, this species was known from two areas: the Rouge River valley in Toronto (two populations) and the Royal Botanical Gardens in Hamilton (five sub-populations). Most populations in 1986 consisted of from several hundred culms to several hundred clumps.

Three of the seven populations and sub-populations could not be found in 1999 despite searches by several people. Three other populations were relocated in the present study but they have declined by at least 50%. A seventh population has not been searched for since 1986. Bashful Bulrush has been specifically searched for in a number of other areas by several experienced field botanists, however, no new sites have been found since 1986.

Limiting Factors and Threats

The main limiting factor for Bashful Bulrush appears to be the lack of suitable habitat. The Ontario range of the plant coincides with one of the most highly urbanized parts of the province. The Toronto sites are vulnerable to the digging of coyote or fox dens. Trampling by hikers and shading by canopy closure and shrub growth, such as from the alien honeysuckles (Lonicera tatarica and L. morrowii) at some sites, are ongoing threats.

Existing Protection

No formal protection exists.