Rare Species Guide

  Synonyms

Sagittaria calycina

  Basis for Listing

Perhaps the major reason native plant species become rare in Minnesota is loss of habitat. In some cases, the loss of habitat can become so acute it threatens the continued existence of the species within the state. This is certainly the case with Sagittaria montevidensis ssp. calycina (hooded arrowhead). The habitat under consideration is prairie wetlands, in all forms, including small and large-size lakes, ponds, and marshes as well as prairie streams and rivers. All of these habitats can, to one extent or another, provide habitat for S. montevidensis ssp. calycina, and all have suffered severe losses because of human activities (Minnesota's Remaining Native Prairie).

At this time, S. montevidensis ssp.calycina is known to occur at only a few scattered sites in Minnesota (Eastern Broadleaf Forest and Prairie Parkland provinces). All the sites are high-quality habitats that have survived the activities of humans, with little disturbance thus far.; hence, in 2013, S. montevidensis ssp.calycina was listed as a threatened species in Minnesota.

  Description

There are six species of Sagittaria in Minnesota. They all have the word “arrowhead” in their common names, even though they do not all have arrowhead-shaped leaves. They do all have white flowers, with 3 petals and 3 sepals, and relatively large basal leaves that emerge from shallow water or wetlands.

Sagittaria montevidensis ssp. calycina is an annual; it lacks rhizomes and tubers. The leaves are arrowhead-shaped or occasionally narrowly elliptic or linear, 5-24 cm (2.0-9.4 in.) long, (1)4-22 cm ([0.4]1.6-8.7 in.) wide. The basal lobes (when present) are about equaling or slightly longer than the apical lobe; the apex of the blade is acutely or obtusely pointed or infrequently rounded. The petioles are 10-75 cm (4-30 in.) long, circular in cross-section, soft and spongy. The scape (stalk of the inflorescence) is initially ascending or spreading, ultimately reclining, 10-70 cm (4-28 in.) long, with 2-6 (commonly 2) whorls of flowers; the pedicels (stalks of the individual flowers) are recurved, especially in fruit, 2-7 cm (0.8-2.8 in.) long, 1.5-10 mm (0.06-0.4 in.) thick. The flowers are bisexual, 1-2 cm (0.4-0.8 in.) across; the sepals are not reflexed, and anthesis is from early July to late September. The achenes (seeds) are 2.2-2.8 mm (0.09-0.11 in.) long, in ± spherical heads, 1-2 cm (0.4-0.8 in.) across at maturity, and tightly enclosed by the sepals; the beak of the achene is 0.5-1.0 mm (0.02-0.04 in.) long, inserted laterally at the upper corner of achene, and is perpendicular to the axis of the achene; the tip of the beak is straight; the achenes mature from early August to mid-October (Haynes and Hellquist 2000).

Of the six species of Sagittaria in Minnesota, this one is the most distinctive. In particular, notice the thick downward curving pedicels, the small cupped flowers, and the sepals that enclose the seed head. Also, the leaf blades are held horizontal to the ground, not vertical like the other species, and the leaves have soft round petioles.

  Habitat

Habitats are found in association with lake shores, river banks, ponds, and marshes, primarily in the prairie region of the state (Eastern Broadleaf Forest and Prairie Parkland Provinces), where water pH is non-acidic. Habitats that produce large exposed mud flats in May and June are excellent habitat. Soft mud (silt), or loose and wet sand are suitable substrates; it does not grow well on firm substrates. These habitats can be short-lived or ephemeral in the sense they may not appear every year. They are dependent on rainfall patterns.

  Biology / Life History

Of the six species of Sagittaria in Minnesota, only S. montevidensis ssp.calycina is an annual; the other species are perennial. It reproduces only by seeds, which are produced by insect-pollinated flowers. The seeds float for some period of time and are dispersed on water currents and by waterfowl. Seeds germinate throughout the growing season, if conditions are favorable (Kaul 1985).

Because S. montevidensis ssp. calycina is an annual, all individuals of a population flower each year, and nearly all flowers are fertile. Under favorable conditions, each individual plant produces flowering scapes throughout the season, until the plant is killed by frost in the autumn. The result is an immense quantity of seeds. One report determined a single plant can produce 414,000 seeds per year (Kaul 1985). The pedicels curve downward as the achenes mature and push the seed head into contact with the water or mud, sometimes burying the seeds. Germination of the seeds is reported to be 100 percent the year they were produced and remains relatively high for at least seven years. This indicates populations may maintain a viable seed bank in the substrate (Kaul 1985). Seeds germinate on exposed mud, silt, and moist sand; and they can also germinate while submerged in 50 cm (20 in.) of water (Kaul 1991).

  Conservation / Management

Healthy and full-functioning habitats of S. montevidensis ssp. calycina are typically inhabited by annual species of plants, rather than perennials. The unstable substrate, rapid siltation, and the extreme seasonal fluctuations in water levels are simply beyond the capacity of most perennials to persist; however, S. montevidensis ssp. calycina thrives under such conditions.

If these conditions are altered by dams, levies, diversions, ditches, or drain tiles (to name just a few examples), habitat conditions may change enough to favor perennial species, especially aggressive species such as Typha spp.(cattails) and the non-native Phalaris arundinacea (reed-canary grass). Unfortunately, S. montevidensis ssp. calycina cannot compete successfully with aggressive perennials.

  Best Time to Search

This species is distinctive enough to allow positive identification anytime during the growing season, depending on local conditions. However, in most years, the prime search period is early July through 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.

Wooten, J. W. 1973. Taxonomy of seven species of Sagittaria from eastern North America. Brittonia 25(1):64-74