Print PageHyoscyamus niger (black henbane) is a solanaceous forb native to Eurasia and introduced into North America. Although this state-listed noxious weed is toxic to both livestock and humans, there is surprisingly little information on its ecology in North America. I address three main topics in this talk. First, I evaluate if introduced populations follow an annual or biennial life cycle. Both life-history strategies are found in the native range, but it is unknown which is present in the U.S. The life-history of introduced plants may contribute to or even drive population dynamics in the introduced range. Second, I examine whether samples of introduced henbane are obligate outcrossers, and evaluate whether seed set depends on sire identity. Early literature reports self incompatibility of European henbane, but information regarding reproductive strategy is not available from the introduced range. Third, I track population sizes in Colorado, Wyoming and Montana, and evaluate trends in population growth to determine whether henbane populations in these western states are growing or declining.
Results/Conclusions
I find that North American populations of black henbane are biennial, but that the requirement for vernalization appears to vary among populations. The pollination experiment reveals that henbane can, in fact, reproduce by selfing, and that there may not be a direct advantage to genetic admixture between populations. Surveys of population characteristics and size reveal that henbane is found exclusively in highly disturbed sites, and that most populations are relatively small (<60 individuals). There is not a pattern of consistent population growth, rather over the course of two growing seasons, sites I tracked increased in size by up to 40 fold or decreased in size by up to 100 fold. Results suggest that black henbane may not pose long term threats to healthy rangeland and native flora.
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