The P50 values for seeds from 10 other Rhododendrons
growing in the grounds ofWakehurst Place ranged from 13.7 d
(R. niveum) to 37.6 d (R. arboreum subset arborea) (Table 1). In
the model fitting, these differences are attributable to
differences in both the theoretical initial viability or ‘potential
longevity’, Ki, of the various seed-lots and the rate at which
viability (in NEDs) is lost, s. If the seed-lots had all started with
the same theoretical initial viability, R. niveum with the highest
estimate for s would have been the longest-lived and R.
argyrophyllum subsp. hypoglaucum and R. fortunei subsp.
discolor the shortest.