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Sweetflag - Acorus americanus
Other Names:
Acorus calamus [misapplied name]
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State Rank Reason (see State Rank above)
This species occurs at the edge of its range in Montana, where it has been collected from two localities in the vicinity of Flathead Lake. Current status of these populations is largely unknown. The species has likely been negatively impacted by hydrologic alterations and devolopment in the area.
Details on Status Ranking and Review
Population Size
Score 2-3 - Very Small to Small: Population size is imprecisely known but is believed to be <10,000 individuals.
Comment Population size is undocumented but is likely to be very small.
Range Extent
Score 3 - Local Endemic or Very Small Montana Range: Generally restricted to an area <10,000 sq. miles (equivalent to the combined area of Phillips and Valley Counties) or <6 Sub-basins (4th code watersheds) Range-wide OR limited to one Sub-basin in Montana
Area of Occupancy
Score 3 - Very Low: Generally occurring in 3 or fewer Subwatersheds (6th Code HUC’s).
Environmental Specificity
Score 1-2 - Moderate to High.
Trends
Score 1-3 - Declining: Species is likely declining though the magnitude of declines is uncertain. Declines may be based upon range extent and/or occupied area in the recent past (approximately 30 years).
Comment Trend data are lacking. However, it would appear likely that declines in the species' distribution and abundance have occurred.
Threats
Score 2-3 - High to Very High.
Comment Habitat loss from development, hydrologic alterations and invasive species.
Intrinsic Vulnerability
Score 1 - Moderate Vulnerability: Specific biological attributes, unusual life history characteristics or limited reproductive potential makes the species susceptible to extirpation from stochastic events or other adverse impacts to its habitat and slow to recover.
Raw Conservation Status Score
Score
15 to 18 total points scored out of a possible 19.
General Description
Scapose rhizomatous perennial with a pleasant odor. Leaves basal, folded, flattened, linear, erect, sheathing below, 50–100 cm long. Inflorescence 20–60 cm; flowers densely clustered on a narrowly cylindrical spike (spadix), 4–7 cm long, subtented by an erect, linear, leaf-like spathe, 15–70 cm long, that appears to be a continuation of the stem. Flowers perfect, tepals 6, separate, brown, ca. 1 mm long; stamens 6; ovary superior, 1- to 3-celled. Fruit a leathery, oblong, glabrous, several-seeded berry 3–5 mm long embedded in the spadix (
Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX ).
Phenology
Flowering occurs in late July and early August. Montana collections were made in early and mid-August.
Diagnostic Characteristics
Sweetflag bears some resemblance to cattail (Typha spp.), but cattail lacks a spathe that extends beyond the inflorescence, and its inflorescence is usually longer and divided into male and female sections. Hardstem bulrush (Scirpus acutus ) may appear vegetatively similar, but its inflorescence is not a finger-like spadix. Acorus calamus , introduced from Europe, is very similar, but the spadix tends to be longer than 7 cm.
Species Range
Montana Range
Range Descriptions
Native
Range Comments
AK to NL south to WA, MT, CO, IA and NY. Known from Flathead and Lake counties (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX ).
Observations in Montana Natural Heritage Program Database
Number of Observations: 12
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
Relative Density
Recency
(Observations spanning multiple months or years are excluded from time charts)
Habitat
Sweetflag occurs in the shallow water of ponds and marshes at lower elevations. Historical collections of this species in Montana are from marshes along lakes and streams, with cattails (Typha sp. ) and Scirpus acutus . Rangewide, it occurs in shallow waters and wetlands, including ponds, marshes, swamps, and quiet riverbanks or floodplains.
Ecology
Sweetflag occurs in the shallow water of ponds and marshes at lower elevations.
Management
Sweetflag grows in relatively stable wet or shallow-water habitats, and would be vulnerable to hydrologic changes associated with impoundments or drainage. Its response to nutrient pollution is not known.
Stewardship Responsibility
Threats or Limiting Factors
STATE THREAT SCORE REASON Phalaris arundinacea ) and Yellowflag Iris (Iris pseudacorus ) occurs at some populations. Hydrological alteration of Flathead Lake is a concern at one site where manipulation of the lake level has the potential to either dewater or inundate plants.
References
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