Carex careyana Torr. ex Dewey
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Basis for Listing
Carex careyana (Carey's sedge) is a perennial sedge that is at the northwestern limit of its range in southeastern Minnesota. It has only been documented from a few locations in Houston, Fillmore, Wabasha, and Winona counties (Blufflands Subsection). All of the populations are on cool, shaded slopes and narrow valley bottomlands. While the species’ extreme rarity was known when it was designated a threatened species in 1996, it was hoped that a few more populations might be found with additional surveys. A comprehensive botanical survey of the region has been completed by the Minnesota Biological Survey, and unfortunately only one additional location of C. careyana has been located. It is now clear that this is one of the rarest and most vulnerable sedges in the state. The species’ habitats are fragile and at risk to a variety of incompatible land use practices, including tree canopy removal, livestock grazing, and road and trail construction. Furthermore, the invasion of nonnative species, particularly Alliaria petiolaris (garlic mustard), poses a significant threat to the few remaining populations. For these reasons, in 2013 C. careyana’s designation was elevated to endangered.
Stems cespitose (growing in dense tufts or clumps) to 60 cm (24 in.) tall. Basal leaves to 40 cm (16 in.) long and 1.8 cm (0.7 in.) wide, shorter than the culms; bases tinged or streaked with reddish purple. Cauline leaves 3-9 cm (1.2-3.5 in.) long, 3-6 mm (0.12-0.24 in.) wide; sheaths at least partially reddish purple. Bracts similar to the cauline leaves, only somewhat smaller; sheaths 0.5-4.0 cm (0.2-1.6 in.) long, tending to have little or no reddish purple color. Pistillate spikes, 1-3 per culm, widely spaced, ± erect, 1-2 cm (0.4-0.8 in.) long; peduncles 0-2.5(10) cm (0-1 (4) in.) long, the upper peduncles often included in bract sheaths, the lower peduncles exserted. Pistillate scales shorter than the perigynia, acute to awned. Perigynia ellipsoid to ovoid, 4.5-6.0 mm (0.18-0.24 in.) long, 2-3 mm (0.08-0.12 in.) wide; veins 13-20 per side, tapering to a straight or slightly askew beak, narrowed to a ± stipitate base. Achenes trigonous, broadly ovoid, 3.0-4.5 mm (0.12-0.18 in.) long; style deciduous.
The only other sedge in Minnesota that has such wide leaves with reddish purple bases is C. plantaginea (plantain-leaved sedge), but the similarity ends there. The stems of C. careyana have both leaves and bracts, both of which are green. The stems of C. plantaginea have just bracts, which are reddish purple.
Since C. plantaginea is so rare, it is more likely that C. careyana will be confused with the common C. albursina (white bear sedge). Both species have unusually wide basal leaves and leafy bracts; however, C. careyana has a reddish purple color at the base of the leaves and on the staminate scales; C. albursina is basically green throughout.
In Minnesota, C. careyana prefers the moist lower portions of rich forested north-facing slopes and moist forested bottomlands along small streams (mesic maple-basswood and wet-mesic hardwood forests). Some populations are found in the vicinity of springs. Populations are associated with common tree species such as Acer saccharum (sugar maple), Tilia americana (basswood), and Fraxinus nigra (black ash) and often with a number of rare herbaceous plants. Known populations of C. careyana range from a few scattered individuals to 100 or more.
Biology / Life History
Carex careyana is a perennial graminoid. It is wind-pollinated and spreads only by seed, though the precise dispersal mechanism is unknown. It sends up its fertile culms early in the spring. These culms continue to elongate throughout May and early June and eventually fall over onto the forest floor and disappear by mid-summer. This may be a dispersal mechanism for the perigynia. By late spring, when the culms are elongating, the plant sends up a flush of basal leaves, which grow through the summer and then overwinter at least partially intact. This life cycle is similar to the other wide-leaved and red-based sedge, C. plantaginea, but different from the common C. albursina, a wide-leaved and brown-based plant that sends up its fertile culms with the basal leaves in mid- to late spring.
Conservation / Management
Carex careyana’s preferred habitat on cool, shaded slopes and narrow valley bottomlands is very fragile and extremely vulnerable to a variety of incompatible land use practices. Potential land uses that could be in conflict with the conservation of this species include livestock grazing, off-road vehicle activities, road and trail construction, and any activities that open the forest canopy. In addition to the potential for direct damage to plants and to the soil, canopy openings can increase the amount of solar energy reaching the forest floor. The subsequent drying and warming of the soil can alter the habitat enough to shift the competitive balance among plant species within the forest community. Such habitat changes could be very detrimental to the survival of C. careyana.
Best Time to Search
The best time to search is during May and June, while C. careyana is in fruit. Fertile culms emerge in late April through early May; perigynia are mature by late May through early June. Fertile culms elongate through May and June; evergreen basal leaves emerge in June and are visible throughout the year.
Conservation Efforts in Minnesota
The Minnesota Biological Survey has been completed in southeastern Minnesota, which makes it unlikely that many additional colonies of C. careyana will be found. Several populations of C. careyana are on State Forest or Wildlife Management Area lands and one is in a State Park.
Welby Smith, MN DNR, 2008 and 2018
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