Megalodonta beckii

A recent collection in Illinois of Megalodonta beckii (Torr.) Greene

Transactions of the Illinois State Academy of Science, Volume 83, 3 and 4, pp. 126-27

Curtis, Linda 1990.


The water marigold, Megalodonta beckii (Torr.) Green (Bidens beckii Torr.) was last reported in Illinois in Grays Lake, Lake County, in 1966 and previously in 1898. It was collected again on August 25, 1988 in Cedar Lake, Lake Villa, Lake Co. by Linda Curtis.


A rare submersed aquatic plant, Megalodonta beckii (Torr.) Greene (Asteraceae) was last found in Grays Lake, Lake County, Illinois by Benjamin L. Dolbeare, of the Illinois State Museum, on August 4, 1966 (Dolbeare 1967). The plant bed was later covered with sand fill to extend the Grays Lake village beach and the only known population in Illinois was apparently lost.

During the drought of 1988, the author discovered Megalodonta beckii in the south bay of Cedar Lake, 16 km north of Grays Lake. While rare in Illinois, the water marigold is found in Wisconsin lakes, the nearest in Rock Lake, Kenosha County (Swink and Wilhelm, 1979).

The collection reported here had yellow ray and disk flowers in a single head that was above the water surface with a one meter depth. After two years of normal rainfall, Cedar Lake had resumed its former level and the plants flowered 15-25 cm below the surface.  Collection data for the specimen that has been deposited at the Illinois State Museum herbarium are: Cedar Lake, Lake County, Illinois, August 25, 1988, Linda Curtis.

Associates that are on the State Endangered and Threatened Plant Checklist (IESPB 1990) are Potamogeton gramineus L., P. praelongus Wulfen, P. strictifolius Benn. and P. robbinsii Oakes.

Aquatic associates not on the State Checklist are P. zosteriformis Fern., P. richardsonii (Ar.Benn.) Rydb., P. pectinatus L., Vallisneria americana Michx., Myriophyllum exalbescens Fern., and M. spicatum L. Others in Cedar Lake are Chara, Ceratophyllum demersum L., Elodea nutallii (Planch.) St. John, Heteranthera dubia (Jacq.) MacM., Potamogeton amplifolius Tuckerm., P. crispus L., P. illinoensis Morong, P. natans L., P. nodosus Poir., P. pusillus L., Najas flexilis (Willd.) Rostk. & Schmidt, N. guadalupensis (Spreng.) Magnus, N. marina L., Nuphar variegatum Engelm., Nymphaea tuberosa Paine, Pontederia cordata L., Ranunculus longirostris Godr. and Utricularia vulgaris L.

Cedar Lake is a natural glacial lake in the Fox River basin. The Illinois E.P.A. study (IEPA 1979) classified it as a Group 3 lake of good conditions and a low problem potential. Cedar Lake’s maximum depth is 12 meters, the average depth is three meters with a surface of 115 ha.


Dolbeare, B.L. 1967. A recent collection of Bidens beckii in Illinois. Transactions, Illinois State Academy of  Science. Vol. 60. No. 2.

Illinois Endangered Species Protection Board. 1990. Checklist of endangered and threatened animals and plants of Illinois. Lincoln Tower Plaza, 524 S. Second St., Springfield, Il.

Illinois Environmental Protection Agency. 1979. Investigations of Illinois surface waters. Limnology of Cedar Lake, Ill. 22 Churchill Rd., Springfield, Il.

Swink, F. and G. Wilhelm. 1979. Plants of the Chicago Region. The Morton Arboretum. Lisle, Il.


 copyright © 2014 Linda Curtis, botanist

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