Ginseng does not spread clonally, and therefore populations expand only through production, dispersal and germination of seeds. Ginseng flowers are not showy, but rather small and whitish-green, bunched together in an umbel. Ginseng flowers mature centripetally; flowers on the outside of the umbel blooming before the flowers located in the center of the umbel. Ginseng has a mixed mating system, meaning that seeds may be produced autogamously or through out-crossing events. Autogamous reproduction means that the plant reproduces via self-fertilization, and outcrossing refers to an ovum being fertilized by an external pollen source. There are two known pollinators of ginseng: syrphid flies and halictid bees. Both of these insects are generalist pollinators, meaning that they visit multiple species of plants when gathering pollen and nectar.
Ginseng berries are bright red when mature, and contain between one or two (occasionally three) seeds. Ginseng seeds are thought to be dispersed primarily by gravity, but in actuality little is known about ginseng dispersal. We set up game cameras to see what animals were visiting ginseng plants while seeds were ripe. Check out what we found below. Of these animals, which one do you think is the most effective disperser of ginseng seeds?
If you said the bird at the upper left, you would be correct! That is a wood thrush, one of the common birds of the deciduous forest understory whose range corresponds very closely to that of ginseng. Thrushes have been caught on camera near maturing ginseng seeds many times, and in fact some of these times, berries were seen in the beak of wood thrushes. But this does not prove thrushes disperse seeds – after all – deer eat ginseng seeds too, but they are destroyed in the gut of a deer. Recently, however, members of our lab performed feeding trials with thrushes using captive birds at the Chattanooga Aquarium. And the answer isâ€¦after seeds are ingested, several minutes later, seeds are regurgitated by the birds in good shape, and they are still viable. Thus we have found our ginseng seed disperser! This has important implications for migration of ginseng across the landscape.
Hruska et al. (submitted).