Apios americana
Author: Medik.

American groundnut

Fabaceae (Pea Family)

Close up of Apios americana by David G. Anderson. See also Google Images.
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Close up of Apios americana by David G. Anderson.
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Taxonomic Comments

Only representative of this genus in Colorado.

Ranks and Status

Global rank: G5
State rank: S1
Federal protection status: None
State protection status: None

[+] Description and Phenology

Illustration of Apios americana from USDA-NRCS PLANTS Database, Britton and Brown 1913. 
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General description: Apios americana is a perennial twining or trailing herbaceous vine, 1 to 5 meters long, with tuberous roots. Its alternate leaves have small stipules and 5 to 7 leaflets. The leaflets are ovate, acute, and 2 to 10 cm long. Plants can be glabrous to pubescent. The flowers are pedicellate and born in axillary racemes. The calyx is green or red tinted. Flowers are 8 to 10 millimeters long with five petals and a papillionaceous corolla. The banner is reflexed, whitish-pink dorsally and reddish-maroon ventrally with brown and green markings in the throat. The wings are pinkish-red and white around the distal edge. Five sepals are united, bilabiate, the upper four lobes very short or absent, the lower lobes longer. Fruits are straight or slightly curved, 5-10 mm long x 6-12 mm wide, usually with 1 seed (Anderson and Spackman 2001, Culver and Lemly 2013, Ackerfield 2015). 

Look Alikes: No other legume in Colorado has the combination of pinnate leaves, creeping habit and purple-brown flowers (Weber and Wittmann 2012, Culver and Lemly 2013).

Phenology: Flowers July-September (Ackerfield 2015).

[+] Herbarium Photos

Images of Apios americana housed at the Colorado State University Herbarium.

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[+] Habitat

Habitat of Apios americana by David G. Anderson.
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Habitat of Apios americana by David G. Anderson.
Click image to enlarge.

Habitat of Apios americana by David G. Anderson.
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In Colorado, one of the known occurrences is located on a river bank, three are adjacent to irrigation ditches, and one is on a shaded, south-facing sandstone cliff on a seep (Anderson and Spackman 2001, Colorado Natural Heritage Program 2016). Moist, shady thickets and along streams (Ackerfield 2015, Culver and Lemly 2013).

Elevation Range: 5,095 - 5,377 feet (1,553 - 1,639 meters)

[+] Distribution

Distribution of Apios americana in Colorado according to mapped land ownership/management boundaries (CNHP 2017, COMaP).
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Distribution of Apios americana in Colorado.
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Colorado endemic: No
Global range: Known from the central and eastern half of the United States, and north into Canada (USDA NRCS 2017).
State range: Five extant occurrences are known in Boulder County. Three are on the banks of irrigation ditches, and two are in natural settings (along South Boulder Creek and on a seep in the White Rocks Natural Area). The species was collected in the Denver area by Alice Eastwood in 1890, and this occurrence is presumed to be extirpated. Dr. William Weber mentioned that it had been documented by unknown botanists in the 1870's in the vicinity or Wray, Colorado.


[+] Threats and Management Issues

Threats to the Colorado populations include ditch cleaning, bank erosion, invasion of exotic species, disturbed stream banks, mowing, haying, and grazing.  Colorado climate scenarios for 2050 suggest temperature will increase by 3-7 F and precipitation may decrease or increase. The impact to any given rare plant habitat is likely to vary. Long-term monitoring that includes weather and soil moisture data is critical to understanding climate impacts.

[+] References

    • Ackerfield, J. 2015. Flora of Colorado. Brit Press, Botanical Research Institute of Texas, Fort Worth, TX. 818 pp.
    • Anderson, D.G. and S.C. Spackman. 2001. Inventory and Status Report of American Ground Nut (Apios americana Medicus) in Colorado. Unpublished report prepared for City of Boulder Open Space by the Colorado Natural Heritage Program, Fort Collins.
    • Britton, N. L. and A. Brown. 1913. An Illustrated Flora of the Northern United States and Canada. 3 vol. Dover Publications, Inc., N. Y. 2052 pp.
    • Colorado Natural Heritage Program and the Geospatial Centroid. 2017. The Colorado Ownership and Protection Map (COMaP). Colorado State University, Ft. Collins, CO.
    • Culver, D.R. and J.M. Lemly. 2013. Field Guide to Colorado's Wetland Plants; Identification, Ecology and Conservation. Colorado Natural Heritage Program, Colorado State University, Fort Collins, 694 pp.
    • Great Plains Flora Association. 1986. Flora of the Great Plains. University Press of Kansas, Lawrence, KS. 1402 pp.
    • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
    • USDA, Natural Resources Conservation Service, PLANTS Database [USDA PLANTS]. http://plants.usda.gov/. Accessed 2017.
    • Weber, W. A. and R. C. Wittmann. 2012. Colorado Flora, Eastern Slope, A Field Guide to the Vascular Plants, Fourth Edition. Boulder, Colorado. 555 pp.

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