MONTH OF HARVEST AND YIELD COMPONENTS OF TEA TREE .2. OIL CONCENTRATION, COMPOSITION, AND YIELD

Changes in the concentration, composition, and yield of oil in coppice growth of tea tree (Melaleuca alternifolia) were assessed when plants were harvested in different months. Oil concentrations in leaves were lower when plants were harvested in July-September than in other mont hs, but biomass yields were higher. Consequently, there was no consist ent effect of harvest month on oil yield. Oil yield varied as much bet ween the same month in different years, as between months within a yea r. The oil concentration in one harvest was positively related to the biomass yield at the previous harvest of the same plants, suggesting t hat a carryover of energy reserves contributed to oil production. The oil concentration was also positively related to the mean air temperat ures over the 3 months before harvest. The proportion of the economica lly significant compounds in oil, terpinen-4-ol and 1,8-cineole, was n ot affected by either the month of harvest or regrowth cycle, but othe r compounds did change. There was a significant loss of monoterpene ol efins from oil which was present at high concentrations.