Rare Species Guide

  Synonyms

Nymphaea tetragona ssp. leibergii, Nymphaea tetragona var. leibergii

  Basis for Listing

Nymphaea leibergii (small white waterlily) has a rather wide geographic range, occurring in several northern states and adjacent Canadian provinces. However, it appears to be rare wherever it occurs. This aquatic species was first discovered in Minnesota at Bald Eagle Lake, Lake County (Border Lakes Subsection) in 1914. It has subsequently been found at approximately 30 additional locations in northern Minnesota (Laurentian Mixed Forest Province), but not without many years of dedicated searching. During the search process, the common N. odorata (American white water lily) was found at over 1,100 locations, providing some indication of the relative rarity of N. leibergii. Most of the discoveries were made in a 1,000 km2 (386 sq. mi.) area within the Glacial Lake Agassiz basin (Agassiz Lowlands Subsection), which includes the western branches of the Rapid River, which drains the Red Lake Peatland. Nymphaea leibergii has been listed as a threatened species in Minnesota since 1984.

  Description

Nymphaea leibergii is one of two species of white-flowered water-lily that occur in Minnesota. The other species is N. odorata, which has larger flowers than N. leibergii. The flowers of N. odorata are 6-19 cm (2-7 in.) wide and have 17-43 petals. The flowers of N. leibergii are 3-7.5 cm (1-3 in.) wide and have 8-17 petals. The floating leaves of N. leibergii are only 2-15 cm (0.8-6 in.) wide, while those of N. odorata are 5-50 cm (2-20 in.) wide. There is significant overlap between large leaves of N. leibergii and small leaves of N. odorata, which makes identification of sterile specimens tentative. Another possible problem to specimen identification is hybridization. Although hybridization has not been documented in Minnesota, it has been reported from New England (Hellquist and Barre 2003).

There is a closely related species in Canada named N. tetragona, which has not yet been documented from Minnesota. It was previously thought they were the same species but determined to be distinct in 1988 (Wiersema 1996, 1997). Nymphaea tetragona differs most obviously in having a reddish-purple stigmatic disc, whereas N. leibergii has a yellow disc.

  Habitat

The documented occurrences of N. leibergii in Minnesota are in shallow, protected bays in lakes and in slow-moving streams, especially streams impounded by beaver dams. One site is in a narrow outlet of a small pond surrounded by a graminoid poor fen. The plants are usually rooted in soft sediments beneath 1-2 m (3.3-6.6 ft.) of water, though the water is sometimes deeper. They prefer the outer margin of emergent vegetation, which typically consists of Zizania palustris (northern wild rice), Sagittaria spp. (arrowhead), Schoenoplectus spp. (bulrush) and Typha spp. (cattail). The species frequently occurs with N. odorata and Nuphar spp. (yellow pond-lily).

  Biology / Life History

The flowers of N. leibergii are borne above the water surface. They are open for only a few hours in the afternoon of each day, and they are pollinated by a variety of flying insects, mostly beetles, small flies, and small bees. After pollination, the peduncle twists into a spiral and pulls the developing fruit below the surface. The fruit matures in 3 to 4 weeks. Upon ripening, the fruit ruptures and the seeds eventually fall to the substrate and germinate the following spring (Hellquist and Barre 2003). Although seeds normally fall near the parent plant, dispersal of some seeds a greater distance via water currents would seem likely. It also seems likely that, on occasion, a rhizome may become uprooted and float downstream, taking root wherever suitable habitat is found (Wiersema 1988). It is unknown how stable populations of N. leibergii are. They may fluctuate with local beaver (Castor canadensis) populations, which appear to provide habitat by building dams.

  Conservation / Management

Exotic plant species such as Lythrum salicaria (purple loosestrife) have been known to choke out N. leibergii (United States Forest Service 2000), though this is not known to have occurred in Minnesota. Other exotic species such as Myriophyllum spicatum (Eurasian watermilfoil), Potamogeton crispus (curly-leaf pondweed), and Butomus umbellatus (flowering rush) must also be considered threats to the habitat of N. leibergii.

Although populations of N. leibergii have been found in ponds that formed upstream of permanent dams, it would be a mistake to assume that building a dam downstream of an existing population would be beneficial for the species. There are too many variables involved in stream dynamics to predict a long-term positive outcome. Human and terrestrial disturbances such as boat wakes, herbicide application, water warming, wild rice management, oxygen depletion, and siltation are also potential problems for this species.

  Best Time to Search

The best time to search for Nymphaea leibergii is when it is in flower, from July to mid-August.

  Authors/Revisions

Welby R. Smith (MNDNR), 2021

(Note: all content ©MNDNR)

  References and Additional Information

Hallquist, C. B. 2003. Nymphaea leibergii Morong (Pygmy Water-lily): conservation and research plan for New England. New England Wild Flower Society, Framingham, Massachusetts. 20pp.

U.S. Forest Service. 2000. Population viability assessment in forest plan revision. Questions for plant population viability assessment panel: Nymphaea leibergii. U.S. Forest Service, Region 9, Superior National Forest, Duluth, Minnesota.

Wiersema, J. H. 1988. Reproductive biology of Nymphaea (Nymphaeaceae) Annals of the Missouri Botanical Garden 75:795-804.

Wiersema, J. H. 1996. Nymphaea tetragona and Nymphaea leibergii (Nymphaeaceae): two species of diminutive water-lilies in North America. Brittonia 48(4):520-531.

Wiersema, J. H. 1997. Nymphaea. Pages 71-77 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 3. Oxford University Press, New York, New York.