A SEED PRODUCTION EXPERIMENT WITH PINUS RADIATA

Abstract

SUMMARY A study of seed production of Pinus radiata D. Don. has been made in two stands in Gippsland, Victoria, after a heavy thinning at nine years. It has shown that seed production per acre increased five-fold in the five years after a thinning to the best 100 trees per acre. At the same time the seed production of the 100 best trees per acre in unthinned adjacent stands decreased slightly. A heavy annual application of NPK fertilizer increased diameter and crown growth but did not increase seed production. The results of this experiment suggest that seed from a “seed production area” would cost about the same as seed of similar genetic quality from trees selected to the same standards of vigour, form and health in routine plantation, but if circumstances permitted clear-felling each year in a seed production area the seed would probably be cheaper. It is recommended that while foresters are waiting a few years for the large quantities of genetically superior seed from “seed orchards” they should establish seed production areas by heavy thinning, and clear-fell small areas for seed after five years. The results of this experiment suggest that the annual yield of a seed production area or a “seed orchard” will probably be more than 20 lb per acre.