Rare Species Guide

  Basis for Listing

Sagittaria brevirostra (short-beaked arrowhead) is endemic to the central United States, and it reaches Minnesota at the northern extreme of its range. Although it is reported to be common in portions of its range (Beal et al. 1982), it is very rare in Minnesota. Its primary habitat is prairie wetlands, which have experienced a dramatic decline in the past century (Minnesota's Remaining Native Prairie). While it is unknown if S. brevirostra was ever common in Minnesota, it is now clearly very rare in the state. It exists here as small and isolated populations in sensitive wetland habitats (Eastern Broadleaf Forest and Prairie Parkland Provinces).

In Minnesota, there are six species of Sagittaria and all serve as indicators of healthy wetland habitats. They do not thrive in what the Minnesota Pollution Control Agency has called “impaired waters”.  Of all the species of Sagittaria that occur in the state, S. brevirostra is the rarest and the most vulnerable to pollution and habitat degradation.

Given the species’ unique habitat requirements and the vulnerability of the few known populations to degradation or destruction, S. brevirostra was listed as an endangered species in 2013.

  Description

Sagittaria brevirostra is a perennial member of the arrowhead genus. Like many species of this genus, S. brevirostra has conspicuous white flowers and large basal leaves, with the classic “arrowhead” shape, The leaf blades can grow to be 12-40 cm (5-16 in.) long and 12-25 cm (5-10 in.) wide; basal lobes of the leaf are consistently 20-80% longer than the apical lobe; the apex is pointed or somewhat rounded. The petioles are 25-110 cm (10-43 in.) long and are many-angled in cross-section. The scape (stalk of the inflorescence) is erect, 40-120 cm (16-47 in.) long, with 4-14 whorls of flowers. The pedicels (stalks of the individual flowers) are 1-2 cm (0.4-0.8 in.) long and 0.5-1.5 mm (0.2-0.6 in.) thick. The bracts at the base of each whorl are lanceolate, flat, 15-30 (70) mm (0.6-1.2 [2.8] in.) long, and 3-7 mm (0.1-0.3 in.) wide at base; the apex is narrowly pointed. The flowers are unisexual, the male are above the female on the scape, they are 1.5-3.0 cm (0.6-1.2 in.) across; the sepals are ± reflexed, anthesis is from early July to mid-September. The achenes (seeds) are 2.3-3.4 mm (0.09-0.13 in.) long and arranged in spherical heads, 10-20 mm (0.4-0.8 in.) across at maturity; the beak of the achene is 0.8-1.2 mm (0.03-0.05 in.) long and is inserted laterally at the upper corner of the achene and grows upwards at an angle of about 45 degrees, then the tip curves upward; achenes mature from late July to mid-October (Bogin 1955; Haynes and Hellquist 2000.)

Sagittaria brevirostra is superficially similar to S. latifolia (broadleaf arrowhead) and the terrestrial form of S. cuneate (arumleaf arrowhead), and it is not impossible to find all three species growing together. One distinctive feature of S. brevirostra is the basal lobes of the leaves are 20-80% longer than the apical lobe. This is a feature that can be seen in the field.

  Habitat

In general terms, S. brevirostra is a species of the prairie biome (Beal et al. 1982), though it is not strictly a prairie species. The three recent records of S. brevirostra are from three somewhat dissimilar habitats. One is a small spring-fed stream on the bottomlands of the lower Minnesota River; one is the backwaters of the Mississippi River near St. Paul; one is in a small flowage between prairie marshes in the southwest corner of the state. All three of the habitats are in shallow and slow-flowing non-acidic water over a substrate of silt and occur in full sun or partial shade. The habitats are not greatly dissimilar to those where S. latifolia or S. cuneata occur in southern Minnesota. Indeed, all three species of these Sagittaria species could be found in the same habitat, even growing side-by-side.

  Biology / Life History

Sagittaria brevirostra is a perennial species of shallow wetlands. It reproduces by seeds that are produced in insect-pollinated flowers and by subterranean tubers that are produced by the rhizomes. The rhizomes themselves and the roots are annual structures that die at the end of each season, only the seeds and tubers survive the winter.

Sagittaria brevirostra has been reported to produce as many as 56 flowers per plant and 1,240 seeds per flower, for a total of almost 70,000 seeds per plant. Germination rate has been reported to be near 100 percent during the year following seed production but falls very quickly after one year, indicating this species probably does not retain a bank of viable seeds in the soil. Although progeny from tubers probably produce flowers their first year, seedlings probably do not (Kaul 1985).

Bogin (1955) claims evidence of hybridization between many Sagittaria species that occur in Minnesota, but hybridization in S. brevisrostra is not apparent in Minnesota populations or in herbarium specimens collected in Minnesota.

Populations of S. brevirostra are reported to remain relatively stable from year to year, when compared to annual species of the genus (Kaul 1991). It has also been reported that S. brevirostra can retain relatively stable populations despite fluctuations in water levels (Kaul 1991). This is interpreted to refer to normal seasonal fluctuations of water levels that are characteristic of prairie wetlands.

Although submerged plant species apparently do not compete with S. brevirostra, Typha spp. (cattails) and the non-native Phalaris arundinacea (reed-canary grass) can outcompete S. brevirostra (Kaul 1991).

  Conservation / Management

Maintaining excellent water quality and natural hydrological regimes is absolutely essential for the survival of S. brevirostra populations in Minnesota. Any degradation or alteration of conditions would almost certainly tip the competitive balance in favor of invasive species, particularly Typha spp. (cattails) and the non-native Phalaris arundinacea (reed-canary grass). There are countless examples of prairie wetlands that originally supported a diverse assemblage of native species that now support nothing except cattails and reed-canary grass. Reversing the process to eradicate the invaders and bring back the natives has been tried many times but is virtually impossible, which makes saving the few remaining healthy wetlands a high priority.

  Best Time to Search

It can be difficult to identify the various species of Sagittaria with just the flowers and leaves, so the best time to search for S. brevirostra is when the seed heads are mature, from late July to mid-October.

  Authors/Revisions

Welby Smith (MNDNR), 2018

(Note: all content ©MNDNR)

  References and Additional Information

Beal, E. O., J. W. Wooten, and R. B. Kaul. 1982. Review of the Sagittaria engelmanniana complex (Alismataceae) with environmental correlations. Systematic Botany 7(4):417-432.

Bogin, C. 1955. Revision of the genus Sagittaria (Alismataceae). Memoirs of the New York Botanical Garden 9:179-233.

Haynes, R. R., and C. B. Hellquist. 2000. Sagittaria. Pages 11-23 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 22. Oxford University Press, New York, New York.

Kaul, R. B. 1985. Reproductive phenology and biology in annual and perennial Allismataceae. Aquatic Botany 22(2):153-164.

Kaul, R. B. 1991. Foliar and reproductive responses of Sagittaria calycina and Sagittari brevirostra (Alismataceae) to varying natural conditions. Aquatic Botany 40(1):47-59.

Minnesota Department of Natural Resources. 2005. Field guide to the native plant communities of Minnesota: the eastern broadleaf forest province. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 394 pp.

Minnesota Department of Natural Resources. 2005. Field guide to the native plant communities of Minnesota: the prairie parkland and tallgrass aspen parklands provinces. Ecological Land Classification Program, Minnesota County Biological Survey, and Natural Heritage and Nongame Research Program. Minnesota Department of Natural Resources, St. Paul, Minnesota. 362 pp.

NatureServe. 2009. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia.