I found the same Australian link for research on the allelopathic effects of Chromolaena that Greene gave earlier in the thread, which says:
"Weed seed germination was inhibited by siam weed extract more than crop seed germination. Maize seed germination was not hindered by siam weed extract while on cowpea and soybean, 14 and 8 percent reduction in seed germination, respectively was recorded when compared with the untreated control. Percent reduction in germination in siam weed treated with the extract was 87 %, when compared with the untreated control . Siam weed extract had some inhibitory effect on soybean growth at the later stage of crop growth, while the growth of maize, cowpea, tridax and siam weed itself was stimulated by siam weed extract."
Allelopathic Effect of Siam Weed (Chromolaena odorata) on Seed Germination and Seedling Performance of Selected Crop and Weed Species
This confirms that not all seeds are affected by it, since corn (maize) was not.
