Mullein seeds can stay in soil without sprouting or spoiling longer than seeds of other plants. This was revealed in an experiment started in 1879 by a botany professor at Michigan University, William James Beal, which is still being conducted today. The professor took the seeds of clover, shepherd’s purse, plantain, mullein, and mallow – in total 21 weeds, placed them in bottles with wet sand and buried them in the university campus. Until the end of his life, he dug out one bottle every five years and placed the preserved seeds in conditions favorable for germination. After his death, the initiative was taken over by his students and colleagues, who extended the check interval, first to 10 and then to 20 years. When checked in 1940 and 1960, only mullein sprouted. In 1980, mallow also grew. In the latest check in 2000, only mullein sprouted. The next check is scheduled for 2020. There are five more bottles left.