Wild Rice
Wild Rice, on Manoomin in the Ojibwe language, is a wetlands grass found in a wide range in the northwoods. It was a staple in the Native American diet, and has found favor among the general population. It is a popular good item for tourists to take home from the region.
A report prepared by the Minnesota DNR, Natural Wild Rice in Minnesota [see at the Documents Tab, above], provides an excellent description of wild rice, and the following information is quoted or paraphrased from that report:
Native North American wild rice is classified as a grass in the family Poaceae and the genus Zizania. The most common species throughout Minnesota is northern wild rice, or Zizania palustris. A less frequently occurring variety is southern wild rice, or Zizania aquatica. Both of these species are native only to North America.
While the historical range of natural wild rice from New England to the Dakotas, its specific occurrence and abundance is in large part dependent on local environmental conditions. For example, clear to moderately colored (stained) water is preferred, as darkly stained water can limit sunlight and may hinder early plant development. Wild rice grows within a wide range of chemical parameters (i.e. alkalinity, salinity, pH, and iron. However, productivity is highest in water with a pH of 6.0 to 8.0 and alkalinity greater than 40 ppm. While researchers have observed that natural wild rice stands are relatively nutrient rich, excess levels of some nutrients, especially phosphorus, can have significant adverse effects on productivity. Natural wild rice generally requires some moving water, with rivers, flowages, and lakes with inlets and outlets being optimal areas for growth. Seasonal water depth is critical, however. Water levels that are relatively stable or decline gradually during the growing season are preferred. In particular, abrupt increases during the early growing season can uproot plants.
Wild rice grows well at depths of 0.5 to 3 feet of water, although some plants may be found in deeper waters. Shallower sites can allow strong competition from perennial emergent plant species, while deeper sites can stress wild rice plants and limit seed production. Although wild rice may occur in a variety of lake bottoms, the most consistently productive stands are those with soft, organic sediment. Nitrogen and phosphorus are limiting nutrients for wild rice.
As an annual plant, natural wild rice develops each spring from seeds that fell into the water and settled into the sediment during a previous fall. Germination requires a dormancy period of three to four months of cold, nearly freezing water (35° F or colder). Seeds are unlikely to survive prolonged dry conditions.
Seed germination typically occurs when the substrate and surrounding water temperatures reach about 40° F. Depending on water depth, latitude, and the progression of spring weather, wild rice germinates in Minnesota sometime in April, well ahead of most but not all perennial plants. Within three weeks, the seedlings develop roots and submerged leaves. The emergent stage begins with the development of one or two floating leaves and continues with the development of several aerial leaves two to three weeks later. The floating leaves appear in late May to mid June, again dependent on water depth, latitude, and weather. Because of the natural buoyancy of the plant, it is at this stage of growth that wild rice is most susceptible to uprooting by rapidly rising water levels. Plants can be significantly stressed even when they remain rooted. Natural wild rice begins to flower in mid to late July in thenorthwoods. Flowering times are dependent on both day length and temperature. Flowers are produced in a branching panicle. Female flowers (pistillate or seed-producing) occur at the top of the panicle on appressed branches. Male flowers (staminate or pollen-producing) occur on the lower portion of the panicle on nearly horizontal branches. Natural wild rice is primarily pollinated by wind. High temperatures and low humidity can negatively affect fertilization rates.
Cross-pollination is typical in natural wild rice stands because female flowers develop, become receptive, and are pollinated before male flowers on the same plant shed pollen. Crosspollination is further enhanced by plant-to-plant variation in flowering times within stands. This cross-pollination within and among wild rice populations helps to preserve the genetic variability and thus biologic potential for wild rice to adapt to changing conditions such as the highly variable climate of the Great Lakes region.
The genetic variability that exists today in natural wild rice may be a critical determinant of whether stands of wild rice can adapt to long-term changes in regional climate. Studies in northern Wisconsin found sufficient genetic diversity among geographically distinct stands of natural wild rice to identify four regional populations. The degree of diversity within stands varied widely as well, with larger and denser stands having greater diversity. [Ref. in original: Waller, D. M., Y. Lu, and P. David. 2000. Genetic variation among populations of wild rice (Zizania palustris). Pages 122-135 in Proceedings of the Wild Rice Research and Management Conference. Great Lakes Indian Fish and Wildlife Commission, 7-8 July 1999, Carlton, Minnesota, USA.]
Wild rice seeds are visible two weeks after fertilization, and they mature in four to five weeks. Immature seeds have a green outer layer that typically turns purplish black as the seed reaches maturity. Seeds begin ripening at the top of the stem and then ripen over several days on an individual plant. Plants within a stand ripen at different times because of genetic and developmental variation. In general, natural wild rice in rivers ripens earlier than that in lakes, rice in shallow waters earlier than that in deeper waters, and rice in northern Minnesota earlier than that in more southerly stands. This staggered maturation process means that ripe seeds may be available within individual stands for several weeks, and across the entire range of natural wild rice in the northwoods for a month or longer. This extended period of shattering, or dropping of ripened seed, is an important mechanism to ensure that some seeds will survive environmental conditions and perpetuate the natural stand. The entire process, from germination of a new plant to dropping of mature seeds, requires about 110 to 130 days, depending on water and air temperatures and other environmental factors.
Not all wild rice seeds germinate the following year. Seeds may remain dormant in the bottom sediment for many years to several decades if conditions are not suitable for germination. This mechanism allows wild rice populations to survive through years of high water levels or storms that reduce or eliminate productivity. Moreover, natural wild rice can germinate and re-colonize sites after other species have been reduced or eliminated by environmental disturbance.
Even under ideal growing conditions, populations of natural wild rice undergo approximately three to five year cycles in which productivity can vary greatly. Highly productive years are frequently followed by a year of low productivity, that is then followed by a gradual recovery in wild rice yield.
Oscillations in wild rice productivity may be caused in part by the accumulation of old straw from previous growth that inhibits plant growth and seed production. In particular, the amount of wild rice straw, its stage of decay, and its tissue chemistry likely affect nutrient availability, influence wild rice productivity, and thus drive cycling of wild rice populations. Natural Wild Rice in Minnesota, pp. 12-16
The invasive rusty Crayfish may be a threat to wild rice because of its larger consumption of aquatic vegetation than the native crayfish it has replaced. [Link]; Manoomin: Past, Present & Future, p. 28.
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Comprehensive References
Major References
Minor References
Nixon Lake was closed to ricing in 2019 because of the poor condition of the rice beds, per several DNR email announcements.