- Scientific name: Eleocharis microcarpa Torr.
- Species of Greatest Conservation Need (MA State Wildlife Action Plan)
- Endangered (MA Endangered Species Act)
Description
Bulbils expanding in flowering head. Photo by Betsy Gill.
The tiny-fruited spike-sedge (also known as hair spikerush), Eleocharis microcarpa, is a small (up to 3 dm [1 ft] tall), densely clustered, annual herb with slender, threadlike stems. Although the tiny-fruited spike-sedge and other spike-sedges (also called spike-rushes) superficially resemble the group of plants called “rushes,” they do not belong to the rush family, and are members of the sedge family (Cyperaceae). The spike-sedges have a single, tight cluster of inconspicuous flowers (a “spike”) at the apex of each stem. The stems of spike-sedges appear leafless, as these plants do not have leaf blades (the expanded part of the leaf), but only leaf sheaths (the part which surrounds the stem). Some stems of the tiny-fruited spike-sedge are erect while others arch. This species can reproduce vegetatively when flowers on arching stems are replaced by vegetative propagules called “bulbils.” Occasionally these bulbils will mature before touching the ground giving the impression of branching stems. Our species is further defined as Eleocharis microcarpa var. filiculmis.
To positively identify the tiny-fruited spike-sedge and other spike-sedges (genus Eleocharis), a technical manual should be consulted. It is usually necessary to look at the tiny fruits of the plant under magnification to distinguish the species of spike-sedge. Members of this genus possess a type of fruit called an “achene,” which is hard and nut-like and does not split open to release its seed. Achenes in the spike-sedges are topped by a protuberance (called a “tubercle”), which varies in shape, size, and texture among species. The tiny-fruited spike-sedge is named for its minute achene, which is only 0.5-1.0 mm (0.02-0.04 in) long. It is three-sided and pearly white to grayish at maturity in mid-summer. In contrast, most spike-sedge achenes are brown, yellow, or green. The surface of the tiny-fruited spike-sedge’s achene appears smooth under a hand lens or microscope. The tubercle is quite small in comparison to the achene, and resembles a tiny cap.
There are several common spike-sedges that could be confused with the tiny-fruited spike-sedge. The soft-stemmed spike-sedge (Eleocharis obtusa), which sometimes occurs with the tiny-fruited spike-sedge in Massachusetts, is another tufted annual that differs in having a lens-shaped achene (instead of triangular) and in its more robust appearance. Its stems are usually taller and thicker than the delicate, thread-like stems of the tiny-fruited spike-sedge. Another associated species, the tubercled spike-sedge (Eleocharis tuberculosa), has flattened stems and a tubercle that is much larger than that of the tiny-fruited spike-sedge; in fact, in the tubercled spike-sedge, the tubercle is as large as the achene. A common spike-sedge with very slender stems that also forms dense tufts is the needle spike-sedge (Eleocharis acicularis). It is distinguished from the tiny-fruited spike-sedge by its diminutive stature (only up to 1.2 dm tall, at most), and its long, gray, ornamented achene that is roundish in cross-section, rather than strongly triangular. The slender spike-sedge (Eleocharis tenuis) is thin-stemmed, but the stems are usually 4- to 8-angled (instead of round) and are usually scattered or only loosely clustered. In addition, the achenes of the slender spike-sedge are rough or pitted in appearance when observed under a hand-lens.
Life cycle and behavior
This is an annual species. It produces mature seed from mid-summer to early fall. Occasionally this species produces bulbils instead of achenes that can mature while still in the air, producing the appearance of branching stems. Once the stem arches and touches the ground, these root and become new plants, which are genetically the same as the parent plant.
Population status
Photo by Quinn Towery.
The tiny-fruited spike-sedge is listed under the Massachusetts Endangered Species Act as endangered. It is rare throughout New England and reaches the northern extent of its range in Bristol County, Massachusetts. All listed species are protected from killing, collecting, possessing, or sale and from activities that would destroy habitat and thus directly or indirectly cause mortality or disrupt critical behaviors. Only two populations of this species have been observed in Massachusetts, both occur in Bristol County, and have been observed within the last 25 years.
Distribution and abundance
The tiny-fruited spike-sedge is known to occur primarily along the Atlantic coastal plain from Massachusetts south to Florida, and west to Texas, and inland to Arkansas and Tennessee. There are disjunct populations in Indiana and Michigan. It is considered critically imperiled in Massachusetts, Indiana and Michigan and possibly extirpated in Connecticut. It appears to be secure throughout the rest of its range.
Distribution in Massachusetts. 1999-2024. Based on records in the Natural Heritage Database.
Habitat
Tiny-fruited spike-sedge in habitat. Photo by Quinn Towery.
The tiny-fruited spike-sedge can be found growing in open, acidic, often sandy, seasonally wet areas of the coastal plain. It appears to be disturbance-adapted and is found in Massachusetts in abandoned sandpits. Other plants it is known to occur with include tubercled spike-sedge (Eleocharis tuberculosa), soft-stemmed spike-sedge (Eleocharis obtusa), Plymouth gentian (Sabatia kennedyana), pondshore rush (Juncus pelocarpus), slender-leaved goldenrod (Euthamia caroliniana), twig-sedge (Cladium mariscoides) and three-way sedge (Dulichium arundinaceum).
Healthy habitats are vital for supporting native wildlife and plants. Explore habitats and learn about conservation and restoration in Massachusetts.
Threats
It is adapted to thrive in disturbed soil, yet too much disturbance, such as through extensive off-road vehicle use of the habitat, could be detrimental to large numbers of existing plants. Too little disturbance and other species will create too much shade for it to grow.
Conservation
Both Massachusetts populations need to be surveyed regularly, and potential management needs noted. This species should be searched for in additional locations in disturbed wetland areas with sandy soil, such as borrow pits and old cranberry bogs. The best time to survey this species is mid-to-late summer.
Management
As for many rare species, exact needs for management of tiny-fruited spike-sedge are not known. The following comments are based primarily on observations of populations in Massachusetts. Because this spike-sedge is found in human-created habitats, it presents an interesting management challenge. Because of its annual, ruderal nature, it is expected that this species will colonize nearby, newly-created disturbances over time. To maintain the tiny-fruited spike-sedge in existing locations, succession should be halted, the area opened, and the sandy soil exposed to encourage germination of the achenes of this annual species. It is known to respond positively to both soil disturbance and fire.
Research needs
It is not known how long the seed will remain dormant but viable if other vegetation shades the habitat. Will the seeds sprout when a disturbance occurs after several years if appropriate conditions are present? It is not known how closely related the populations in Massachusetts are to populations further south where the species is more common and genetic work is needed to determine that.
References
Fernald, M. L. 1950. Gray’s Manual of Botany, Eighth (Centennial) Edition—Illustrated. American Book Company, New York.
Haines, A. 2011. Flora Novae Angliae – a Manual for the Identification of Native and Naturalized Higher Vascular Plants of New England. New England Wildflower Society, Yale Univ. Press, New Haven, CT.
Hickler, Matthew G. 2003. New England Wild Flower Society. “Eleocharis microcarpa var. filiculmis Torrey Tiny-fruited Spikerush.” Conservation and Research Plan for New England.
NatureServe. 2025. NatureServe Network Biodiversity Location Data accessed through NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available https://explorer.natureserve.org/. Accessed: 10/19/2025.
POWO (2025). Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; https://powo.science.kew.org/ Accessed: 10/19/2025.
Seymour, Frank C. 1969. The Flora of New England, First edition. Charles E. Tuttle Company, Inc. Tokyo, Japan.
Contact
| Date published: | May 7, 2025 |
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| Last updated: | October 28, 2025 |