|Dacrydium cupressinum Rimu|
Dacrydium cupressinum Rimu
Along with the other New Zealand podocarps rimu is dioecious. The most striking feature of the reproductive cycle of rimu is the periodicity of seed fall. There is a pronounced year to year periodicity in the volume and viability of rimu seed. Every 3 or 4 years a bulk setting of seed occurs (called mast years). This could be due to some environmental factor such as cool temperatures 2 years previous to seed fall when the seed is being set plus warm temperatures in the summer of seed fall. The reproductive effeciencies of scale assosciated with synchronizing male and female reproductive effort may favour masting in this dioecious species.Seedfall is from mid-March to the end of April. There is often a high rate of empty or undeveloped seed. The seed is adapted well to bird dispersal which occurs from April to June. The base of the seed is joined to a sweet tasting fleshy receptacle which is swallowed along with the seed and passes through the gut, being excreted hopefully some distance from the parent tree. Birds which have been observed eating Rimu berries include: Tui, Bellbird, Whiteheads, Kereru, blackbirds, starlings and thrushes.
Rimu seeds are normally dormant for at least 30 days and sometimes much longer prior to germination.When the seeds are sown in a glasshouse in may germination usually occurs the following spring.The seeds are considered to remain viable for no more than 12 months after sowing.