Overview
The Minnesota dwarf trout lily (Erythronium propullans) is a forest wildflower found in Goodhue, Rice and Steele counties, Minnesota. Because it is known only from this small area, the dwarf trout lily is considered a Minnesota endemic, meaning a species that grows in Minnesota and nowhere else on earth.
The Minnesota dwarf trout lily is an endangered species, meaning that it is in danger of becoming extinct. Identifying, protecting and restoring endangered and threatened species is the primary objective of the U.S. Fish and Wildlife Service, through the endangered species program.
Stressors
The dwarf trout lily was listed as a federally endangered species in 1986 (51 FR10521), and is still jeopardized with the possibility of extinction. This plant has probably always been rare, but is presently known to occur in only three counties in Minnesota. Such a narrow range allows little leeway for a wild species to adapt to new threats or changing environmental conditions. Today, housing and agricultural developments, increased pressure for recreational land use and large-scale precipitation and flooding, due to climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change all mount increased pressure on this species. Expanding populations of non-native invasive plants, like garlic mustard, also increase the chances that the few remaining populations could be destroyed. In addition to direct destruction of plants by human activities, the increased conversion of floodplains to cropland also reduces the probability that plants that are dislodged by upstream floodwaters will find suitable downstream habitat. Disturbance of uphill areas can cause erosion and siltation in areas where the lilies occur. New threats, which were not addressed in the 1987 recovery plan include non-native plant species, including honeysuckle (Lonicera spp.), buckthorn (Rhamnus cathartica) and dame’s rocket (Hesperis matronalis). The 5-year review in 2021 noted additional threats from developmental anomalies, increased flooding and perhaps, the offsite application of herbicides for things like lawn treatments.
Climate change, and associated large-scale precipitation events throughout the season, is a new and emerging threat that greatly alters floodplain habitats by scouring away the finer textured soils where dwarf trout lily grows, as documented by Derek S. Anderson in 2019. Such intense flood events deposit sand and other sediments, as much as 12 inches, on top of known populations, create new channels that pass through previously documented populations and erode slopes where populations occur, Anderson noted further.
Genetic uniqueness
Like all native species, the Minnesota dwarf trout lily has its own specific niche in the ecosystem and relationships to other plants and animals with which it lives. As such, it is a part of the whole, a part whose unknown utility is best expressed in the words of Wisconsin conservationist Aldo Leopold in his collection of journals in the book Round River, "To keep every cog and wheel is the first precaution of intelligent tinkering.” The Minnesota dwarf trout lily possesses a genetic and chemical makeup unlike that of any other plant. It is known to be most genetically similar to the closely related white trout lily from which it is believed to have evolved no more than 9,000 years ago.
Conservation Measures
The recovery plan for the Minnesota dwarf trout lily was finalized in 1987. Recovery activities include surveys for additional populations, monitoring existing populations, conducting research on the species biology and protecting existing populations. The Minnesota dwarf trout lily's woodland habitat is a mature, self-perpetuating forest ecosystem that requires little or no manipulation of the vegetation. For this reason, most management activities are directed toward protecting dwarf trout lily colonies from erosion which is caused by upstream activities or from direct damage caused by human traffic. For example, a retaining wall was constructed to stabilize the bank of Prairie Creek at Nerstrand Woods State Park, where spring flood waters were undermining dwarf trout lily colonies. A boardwalk was also constructed at Nerstrand Woods Sate Park for visitors to observe and photograph the Minnesota dwarf trout lily without disturbing colonies of this endangered plant. Additionally, some sites are closed to motorized traffic to prevent soil compaction or disturbance. More details on monitoring, trends and status of the dwarf trout lily are provided in the 2011 and 2021 5-year reviews for the species.
Scientific Name
Identification Numbers
Characteristics
Physical Characteristics
The blooming plant is readily identified by the very small size of its flowers. Flowers of the dwarf trout lily are about the size of a dime or less (8 to 14 mm long) and are pale pink, with a variable number of petals. Most members of the lily family have six petals, but dwarf trout lilies may have four, five or six. Typically, dwarf trout lily stems are about the width of a pencil line. Dwarf trout lily buds are about the size of a grain of rice. The elliptic to lanceolate leaves are slightly mottled and paired in flowering plants, but single in vegetative plans and range from 1 to 3 centimeters in width, as described in the 1987 recover plan. Dwarf trout lily buds are about the size of a grain of rice.
Dwarf trout lily flowers are typically pale pink color, but the color ranges from pinkish to pale violet to white or gray white, as described in the 1987 recovery plan. The fruit often has two carpels and remains in a nodding position. Dwarf trout lily have tapering green leaves lightly mottled with a greyish-white pattern. The elliptic to lanceolate leaves are slightly mottled and paired in flowering plants, but single in vegetative plans.
Life Cycle
The Minnesota trout lily is a spring ephemeral plant which flowers from late April to mid-May, as described in the 1987 recovery plan. Below ground, the bulbs are perennial and renewed by the parent bulb. The flowers are pollinated by small bees, including the Carlinville miner bee, Andrena carlini, as documented by J.A. Banks in 1980.
Like spring beauties and Dutchman's breeches, trout lilies are spring ephemerals, meaning that they are adapted to flower and grow before the deciduous trees develop their leaves. When summer shade darkens the forest floor, these plants have already bloomed, generated their food reserves for the coming year and lost their leaves. The aboveground parts of the plant typically wither when the tree canopy leafs out by mid-May or June.
Published research reveals that the Minnesota dwarf trout lily rarely, if ever, produces seeds, as documented by J.A. Banks in 1980 and later by T. Morley in 1982. It appears that this species reproduces largely, if not entirely, by asexual means through the production of offshoots. Attempts to artificially propagate dwarf trout lily generally have been unsuccessful, as noted in the 5-year review in 2021.
J.A. Banks observed in 1980 that dwarf trout lily flowers are pollinated by small bees, including the Carlinville miner bee, Andrena carlini. Until recently, it was assumed that dwarf trout lily reproduces almost exclusively by forming a single runner from a bulb and that bulbs of non-blooming plants do not produce runners, as documented by T. Morley in 1982. Data from introduced populations of dwarf trout lily at Minnesota Landscape Arboretum in Chaska, Minnesota are challenging those assumptions because of a higher growth rate than what could be expected through production of single runners from blooming plants, as documented by N. Sather in 2009.
Habitat
The dwarf trout lily occurs on fewer than 600 acres of woodland habitat, that is characterized by rich slopes, which are dominated by maple and basswood, as well as adjoining floodplains that are dominated by elm and cottonwood.
The species’ distribution is related to the distribution of Decorah shale as the underlying bedrock layer. This is probably because of the finer texture soils derived from Cannon River, Little Cannon River, Straight River, Zumbro River and Prairie Creek, as documented by N. Sather in 2009. The species’ preferred habitat appears to be maple-basswood forests on slopes and ravines or floodplain forests, as noted in the 5-year review in 2011. It has been found that 42% of known populations occur in floodplains that may be prone to flooding at least in some years. Sather noted that another 37% of colonies occur on easily eroded slopes.
Land covered by evergreen trees in cool, northern latitudes. Also called taiga.
Similar Species
There are three species of trout lily in Minnesota: the Minnesota dwarf trout lily, the white trout lily (Erythronium albidum) and the yellow trout lily (Erythronium americanum). All are spring ephemerals. All have tapering green leaves lightly mottled with a greyish-white pattern. Huge patches of leaves with very few flowers are characteristic of trout lilies and are common in all three species.
The leaves of white trout lilies and dwarf trout lilies are very similar and often overlap in size. Therefore, it is difficult, if not impossible, to distinguish between species in large masses of leaves without flowers. However, flowering dwarf trout lilies are distinguished by the very small size of their flowers.
Flowers of the dwarf trout lily are about the size of a dime or less (8 to 14 mm long), pale pink, with a variable number of petals. Most members of the lily family have six petals, but dwarf trout lilies may have four, five or six. Typically, dwarf trout lily stems are about the width of a pencil line, whereas those of white trout lilies are approximately 1 millimeter wide, or closer to the diameter of string or a rubber band.
Geography
The Minnesota dwarf trout lily is a forest wildflower found in Goodhue, Rice and Steele counties, Minnesota. Recorded populations of Minnesota dwarf trout lily occur along the Cannon River, Little Cannon River, Zumbro River, North Fork Zumbro River and Prairie Creek watersheds, as noted in the 5-year review in 2011. N. Sather noted in 2009 that undiscovered populations of E. propullans may exist along “Portions of the Straight River and its tributaries upstream of the Steele County line,” where landowner permission to conduct searches of suitable habitat has yet to be secured “in this highly developable corridor."
Because it is known only from this small area, the dwarf trout lily is considered a Minnesota endemic, meaning a species that grows in Minnesota and nowhere else on earth.
Approximately half of the known dwarf trout lily sites are included in state Scientific and Natural Areas, state or county parks or private preserves such as those of The Nature Conservancy. A large number of dwarf trout lily populations occur on private land where farmers or other landowners have maintained the species by protecting its woodland habitat. Many of these families have entered into a voluntary private registry program that acknowledges their role in preserving the state's rarest plant species.
Timeline
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