Flowering and Fruiting
Bluegum eucalyptus in California flowers from November to April, the wet season (15). In Hawaii, some trees flower throughout the year, but flowering is heaviest in February to March. The flower buds have a warty cap or operculum about 2.5 cm (1 in) in diameter, which falls off, allowing the very numerous stamen filaments to extend in shaving-brush fashion above the cup-shaped base (hypanthium). The yellowish white flowers are pollinated by insects, hummingbirds, and other pollen and nectar feeders. As in almost all eucalyptus, pollen is usually viable before the stigma becomes receptive (8). The fruit, a distinctive top-shaped woody capsule 15 mm (0.6 in) long and 2 cm (1 in) in diameter, ripens in October to March in California, about 11 months after flowering (15). In Hawaii the fruit ripens throughout the year.
Burns, Russell M., and Barbara H. Honkala, technical coordinators. 1990. Silvics of North America: 1. Conifers; 2. Hardwoods. Agriculture Handbook 654 (Supersedes Agriculture Handbook 271,Silvics of Forest Trees of the United States, 1965). U.S. Department of Agriculture, Forest Service, Washington, DC. vol.2, 877 pp.