Soil Seedbank Longevity of a Terrestrial Orchid

Seeds of terrestrial orchid species are small and essentially without food reserves, but data on the longevity in the wild of seed of most orchid species is lacking.

Bill Brumback (New England Wildflower Society) and Jay O’Neil (Smithsonian Experimental Research Center)

Seeds of terrestrial orchid species are small and essentially without food reserves, but data on the longevity in the wild of seed of most orchid species is lacking. In October 2003, packets containing seeds of the Federally Threatened orchid, Isotria medeoloides, small whorled pogonia, were buried within a population of this species in New Hampshire. Seeds packets were removed from the soil for testing in 2007 and again in 2017. Seeds were examined for viable embryos and also tested with Triphenyltetrazolium chloride (TTC) for viability. Results showed that in 2007 over 50% of the seeds remained viable, and by 2017, more than 13 years after burial, the number had only dropped to 42%. There was no evidence of germination or mycorrhizal association in the buried seeds. These results indicate the potential for a persistent soil seedbank for this orchid species, despite its minute seeds. Protocols for ex situ seed banking of many terrestrial orchids have yet to be developed, but in situ soil seedbank experiments with orchid seeds can give clues to the survival potential of a population in the wild.