Reproductive phenology, reproductive traits and the pre emergent reproductive success (PERS) of Welwitschia
mirabilis were studied in plants growing in the Botanical Garden of Portici. The leaves grow throughout the year and
growth is positively correlated to temperature and day length; at flowering, the growth rate slows down. The plants have a
reproductive cycle lasting 9-10 months; male plants form more branches and strobili than females, female strobili are
larger than male ones. Both male and female plants produce cones that differ in the color of the covering bracts. Plants
produce a lot of seeds, but most of them are empty; therefore the seed/ovule ratio is low. Filled and empty seeds are
morphologically similar; filled seeds have high vitality that is maintained for several years. As probable causes of the low
seed/ovule ratio, both pollination and embryo abortion are taken into account; our observations lead us to believe that the
embryo abortion hypothesis is more accurate. However, since each plant may produce a discrete number of cones and
filled seeds are highly viable, ultimately Welwitschia appears to be a rather efficient plant in terms of pre emergent reproductive
success.