Tom Jordan, Extension Weed Science Specialist
This is the fruiting structure of a spurred anoda (Anoda cristata), a weed that is not common in Indiana, but is more likely to be seen in the southeastern part of the state near the river bottoms. This plant is in the mallow family and therefore is related to velvetleaf and prickly sida (tea weed).
Five green outer flower parts (calyx) extend beyond the flattened ring of eight to 20 carpels (seed-bearing structures). Each carpel has a spur at the end; hence the name spurred anoda.
This plant has a low growing, spreading habit and the stems can spread four to five feet from the taproot. The leaves are alternate, 1 1/2 to 3 inches long, and are usually triangular or arrowhead-shaped.
Although this weed has begun to appear more in soybean and corn in recent years in the southeastern part of the state, it is not likely to become a predominant weed problem anytime soon. It is probably more resistant to herbicides that are typically used to control velvetleaf and prickly sida. It is more likely to become established in soybean, particularly where post-emergent herbicides without residual activity are used. It germinates later than velvetleaf, and thus germinates after post-emergence herbicide applications have been applied. You might also want to check the following webpage for more photos of spurred anoda: http://www.rce.rutgers.edu/weeddocuments/anoda.htm.
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