Eucalyptus citriodora, or Lemon Scented Gum, is a stately evergreen tree native to Queensland, Australia. The trees have 2 forms of leaves, the juvenile leaves being lanceolate up to 6 inches (15 cm) long with a rough sandpapery feel (visible on the right side of the image), whereas the adult leaves are light green, glossy, and lanceolate, up to 6 inches (15 cm) long (visible on the left). The adult leaves are known as phyllodes and are more highly drought adapted. In fact, phyllodes do not have a traditional leaf lamina--instead the green leaf blade, in a developmental sense, is an outgrowth of the petiole. Both sets of leaves have a strong lemony scent when crushed. Leaves yield lemon-scented oil, Citonellal used in perfumery. The trunks and branches of this species are powdery white to pinkish and the trunks are usually very straight. In nature the trees will reach from 75-100 ft (20-30 m) tall. They are a very popular tree in California and Arizona. While this species get very big in nature, its size is easily control with selective pruning and container size when grown in the greenhouse setting. The trees are hardy in USDA zones 9-11.
Blooming: Trees bloom in winter in nature, in the greenhouse they bloom in late winter to early spring. The white blooms are not very distinctive. The blooms are followed by woody urn-shaped capsules about 3/8 of an inch (5 mm) wide.
Culture: Eucalyptus citriodora need full sun with a well-drained soil mix for container growing. We use a soil mix consisting of 1 part peat moss to 1 part loam to 2 parts coarse sand. Trees are well watered and allowed to dry slightly before watering again. Most gum trees grow in very nutrient poor soils and fertilizer is not needed; however we fertilize trees in container once during the spring. To control the size of the trees in containers, we do all pruning and repotting in late to early spring after flowering. During the winter months, the temperatures are never allowed to drop below 50°F (10°C) at night. In the landscape, trees are very susceptible to frost.
Propagation: Eucalyptus citriodora are propagated by seed in the spring. The very small seed is surface sown on coarse sand and peat mixture and kept moist. Seeds germinate in 30-45 days at 70°F (22°C).
Eucalyptus citriodora was featured as Plant of the Week December 15-21, 2006.
Guide to Past Plants-of-the-Week:
Cal's Plant of the Week was provided as a service by the University of Oklahoma Department of Microbiology & Plant Biology and specifically Cal Lemke, who used to be OU's botany greenhouse grower and an avid gardener at home as well. If the above links don't work, then try the overview site. You may also like to look at the thumbnail index. ©1998-2012 All rights reserved.