2020 Volume 71 Issue 1 Pages 23-32
Phenological responses in species of Cardamine are often accompanied by morphological changes that result in disagreement among researchers about the taxonomic rank and status of a particular taxon. The gross morphology of two closely related eastern Asian species, Cardamine fallax (O. E. Schulz) Nakai and C. occulta Hornem., was compared by growing plants under controlled photoperiod and vernalization conditions. Response to photoperiod and vernalization in C. fallax and C. occulta explained differences in phenology between the two species under natural conditions. The gross morphology was distinctive between the two species grown under the same conditions, but overlapped when C. fallax was grown in the spring photoperiod-temperature regime and C. occulta grown in the autumn environmental regime. Cardamine fallax is distinct from C. occulta in gross morphology when seasonality in flowering time is taken into account. The findings support the distinction between C. fallax and C. occulta. A survey of herbarium specimens revealed the upper cauline leaves of C. fallax to be moderately or densely hairy, while those of C. occulta were glabrous or sparsely hairy.