Citizen science opportunity: have you seen falcata alfalfa?

By Jonathan O.C. Kubesch, University of Tennessee—Knoxville

Falcata alfalfa (Medicago sativa ssp falcata) is a stunning subspecies of the purple-flowered alfalfa commonly seen in the eastern United States (Figure 1; USDA-NRCS Plant Materials Program, 2015). Falcata alfalfa was introduced to South Dakota from Siberia by an eager professor in the early 19^th century, however, the subspecies has appeared in the Kentucky flora in the time since (Shaw et al., 2020; Smith 1997). Falcata alfalfa improves the quantity and quality of forages for rangeland with tradeoffs for native species richness in South Dakota (Xu et al., 2004). The Kentucky collections may have come in seed bagged from elsewhere, especially as seed production shifted from the region to the Willamette Valley of Oregon (Figure 2).

Falcata alfalfa’s use in rangelands presents a question: why alfalfa has not naturalized into the South? Given it has historically been found in cultivated and disturbed environments, has the species formed any stable populations outside of agricultural use? And given falcata’s success in the High Plains, why hasn’t the species been used in the South?

Falcata is promising given its performance in low fertility conditions (USDA-NRCS Plant Materials Program, 2015). A research project at the University of Tennessee is investigating the horticultural performance of falcata alfalfa in the Southeast. Seed from the United States Department of Agriculture—by way of Canada and originally from eastern Italy—is being grown to study the plant in the eastern United States (Figure 3; USDA PI 631577). Concerns about introducing new plant species into the Southeastern flora prompted this present article. A fair number of plants introduced to the eastern United States have gradually moved outside of agricultural fields, such as tall fescue (Schedonorus arundinaceus), but the subspecies of alfalfa have not escaped and persisted for extended periods in the wild. 

The Tennessee-Kentucky Plant Atlas is a helpful tool for this sort of research (Shaw et al., 2020). Documenting the localities and conditions that falcata alfalfa has been found in the native flora should expound on these questions and theories regarding the species and subspecies persistence in the Southeast. Through the Atlas we can tell that escaped alfalfa does not necessarily take over native habitat in Kentucky and Tennessee in the same way that alfalfa has persisted in the High Plains of South Dakota. However, the Atlas is limited to collections made before 2002 (Shaw et al., 2020). With that in mind, citizen scientists are critical to documenting falcata alfalfa in Kentucky in 2020. The species should be seen where the purple flowered alfalfa occurs, such as disturbed areas and pastures.

Have you seen falcata alfalfa?

To help with this citizen science project, please follow these instructions:

1. Falcata alfalfa is quite similar to the standard alfalfa (USDA-NRCS Plant Materials Program, 2015).
   1. Look for the yellow flowers above ground and a webbed network of roots below ground (Figure 1; USDA-NRCS Plant Materials Program, 2015).
   2. Leaves are trifoliate, and a central crown supports multiple stems, like the standard alfalfa, so flowers are critical for identification.
2. Grassland Oregon (Salem, Oregon) has a wonderful video on the falcata alfalfa they are developing. https://www.youtube.com/watch?v=zUFt_JBdyDc
3. Document the occurrence with photos or iNaturalist:
   1. For iNaturalist, use these instructions from KNPS (2020) https://www.knps.org/2020/02/19/kentucky-botanists-big-year-2020-inaturalist-project/.
   2. Photos should include the flowers, a profile of the whole plant, and the individual stem from above.
4. Contact Jonathan Kubesch at jakubesch@gmail.com with the location and date of the falcata alfalfa sighting.
5. Celebrate spotting a rare, potentially naturalized plant. If found there may be a need to see if the falcata alfalfa persists at a location.

Tracking introduced species in Kentucky’s flora helps to anticipate potential threats to native biodiversity as well as monitor changes in the state’s ecology. European settlement brought a number of species deliberately and unintentionally to Kentucky. The native grasses of the New World were insufficient to meet livestock needs under pioneer management (Cronon, 2003).  The exchange of horticultural and agricultural species continues, as evidenced by the recent scare from Chinese seed mailings, as well as the even greater volume of legitimate sales occurring daily.

Introduced species can sometimes become invasive,  penetrating into natural communities. Invasive species gradually expand beyond areas of introduction and can severely alter the ecosystem dynamics. In Kentucky, Amur honeysuckle (Lonicera maackii) comes to mind as a threat to the native flora. Some introduced species, such as naked ladies, do not move far from their planting space. The pink flowers on bare stalks maintain unnaturally square corners around the foundations of old house sites and old, lightly-used cemeteries. Similarly, white clover may have moved into Kentucky with Daniel Boone and the original settlers.

Alfalfa (Medicago sativa ssp sativa [purple flower] and Medicago sativa ssp falcata [yellow flower]) is the queen of the forage species introduced to the American Southeast (Ball et al., 2015). However, in recent years, alfalfa has proven challenging to establish and maintain without a fair deal of agronomic management. Alfalfa research in agriculture suggests that it is hard to maintain as a farm crop for more than 3-5 years of production (Quinby et al., 2020; White and Lemus, 2015). The explanation of this relatively short lifespan of a perennial grassland plant is a combination of edaphic conditions, pests, and competition.

Alfalfa needs fertile, alkaline soil, and that is one reason that the species has trouble establishing and persisting. In disturbed areas, concrete and gravel might adjust the local soil in favor of alfalfa over other plant species (Figure 4a). The alkaline soils of the High Plains are favorable to alfalfa plants. Because alfalfa maintains a symbiotic relationship with nitrogen-fixing bacteria, phosphorus and potassium often limit the growth possible to these plants (Figure 4b; Quinby et al., 2020). The high demand for these elements often restricts the plant growth.

Alfalfa is susceptible to potato leafhopper and the alfalfa weevil. The alfalfa weevil discouraged the majority of farmers from growing alfalfa in the Southeast in the 20^th century (Gary Bates, personal communication). Herbarium specimens from the wild have shown evidence of the alfalfa weevil.    

Competition between crop species in a mixture is a growing area of research (Nave and Corbin, 2018; Quinby et al., 2020; Kubesch et al., 2020). Light and nutrient resources are the primary focus of competition. Alfalfa appears to function well in grass-legume mixtures, though the budding research literature suggests that alfalfa needs to be planted simultaneously with grasses in order to effectively compete with the grass (Quinby et al., 2020; Tracy et al., 2016). This observed establishment period competition could explain the limited persistence in the wild.

Falcata alfalfa adds a new perspective on an agronomic and ecological challenge in the southeastern United States: what do naturalized populations tell us about introduced species? Often, agronomy is the applied ecology of making genetics and environments compatible for a crop. For farmers and wildflower enthusiasts in Kentucky, Tennessee, and beyond, falcata alfalfa might meet some of the challenges of the Southeast.

Acknowledgements

Thanks to Sarah Grace Holland, Grace Christian Academy, for prompting me to propagate this species for horticultural purposes. Thanks to Grassland Oregon’s team Risa DeMasi and Don Baune for a July tour of their research farm in Salem, Oregon. Thanks to Mason Brock of Austin Peay State University for reviewing this article and helping shape its final form. Special thanks to Adam Zimmerman, University of Tennessee Institute of Agriculture Department of Biosystems Engineering & Soil Science, for providing a scale reference with his boots in Figure 4b.

References

Ball, D. M., Hoveland, C. S., & Lacefield, G. D. (2015). Southern Forages (5th Ed.). Peachtree Corners, GA: International Plant Nutrition Institute (IPNI).

Cronon, W. (2003). Changes in the land: Indians, colonists, and the ecology of New England. New York, New York: Hill and Wang.

Grassland Oregon. (2018). Falcata alfalfa. Salem, OR. https://www.youtube.com/watch?v=zUFt_JBdyDc accessed August 19, 2020.

Kentucky Native Plant Society [KNPS]. (2020). Kentucky Botanists Big Year 2020 iNaturalist Project.  https://www.knps.org/2020/02/19/kentucky-botanists-big-year-2020-inaturalist-project/ accessed August 19, 2020.

Kubesch, J. O. C., Nave, R. L. G., Cui, S., Griffith, A., Bates, G. E., & Butler, D. M. (2020). Optimal forage species selection for southeastern transitional or low-input production. Proceedings of the American Forage and Grassland Council Annual Conference. Greeneville, SC.

Nave, R. L. G., & Corbin, M. D. (2018). Forage Warm-Season Legumes and Grasses Intercropped with Corn as an Alternative for Corn Silage Production. Agronomy 8(199): 1-9. doi:10.3390/agronomy8100199

Quinby, M. P., Nave, R. L. G., Bates, G. E., & McIntosh, D. (2020). Harvest interval effects on the persistence and productivity of alfalfa grown as a monoculture or in mixtures in the southeastern United States. Crop Forage & Turfgrass Mgmt.6:e20018. https://doi.org/10.1002/cft2.20018

Shaw, J., Estes, D., Ruhfel, B., Morris, A. B., & Littlefield, T. R. (2020). Tennessee-Kentucky Plant Atlas. [S.M. Landry and K.N. Campbell (original application development), USF Water Institute. University of South Florida]. University of Tennessee at Chattanooga, Austin Peay State University, University of Michigan, Furman University, and Kentucky State Nature Preserves Commission.

Smith, N. G. (1997). Yellow-blossomed alfalfa on rangeland in South Dakota. Rangelands 19(4): 24-25.

Tracy, B. F., Albrecht, K., Flores, J., Hall, M., Islam, A., Jones, G., Lamp, W., MacAdam, J. W., Skinner, H., & Teutsch, C. (2016). Evaluation of alfalfa-tall fescue mixtures across multiple environments. Crop Sci. 56:2026-2034. 

USDA-NRCS Plant Materials Program. (2015). Plant guide for yellow-flowered alfalfa [Medicago sativa subsp. falcata (L.) Arcang.].

White, J. A., & Lemus, R. (2015). Alfalfa Establishment, Performance, and Persistence in Mississippi When Planted into a Bermudagrass Sward. American Journal of Plant Sciences 6:2220-2226. http://dx.doi.org/10.4236/ajps.2015.613224

Xu, L., Boe, A., Johnson, P., & Kephart, K. (2004). Effects of Naturalized Population of Yellow-flowered Alfalfa on Species Richness and Biomass Production of Native Rangeland. South Dakota Beef Report 2004(19): 99-105.

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Jonathan Omar Cole Kubesch is a graduate student pursuing a master’s degree in crop science at the University of Tennessee. He studied evolution and ecology—as well as agronomy—at the Ohio State University. He works on forages, grasslands, and prairies with a particular passion for native clovers.