Citrus sinensis, or Sweet Orange, forms compact evergreen trees that often reach 40 feet in height. The leaves are elliptical to oblong-ovate, up to 4 inches (10.2 cm) long, with narrowly-winged petioles. Sweet oranges originally come from China and S.E. Asia where they have been cultivated for centuries. They are the most important citrus fruit in cultivation today. There are many cultivars and they are classified by geographic ancestry (Mediterranean oranges, Spanish oranges, ...) or by fruit characteristics (blood oranges, navel oranges, etc.). We are not sure what cultivar we have. We received this tree when it was 12 inches (30 cm) tall, and the tree has now reached 7 feet tall (~2 meters) in a 5 gallon container. They make excellent container plant because size is easily controlled with container size and selective pruning.
Blooming: In the greenhouse, our plant blooms in late spring to early summer. The white flowers are in a cluster at the tips of the branches.
Culture: Citrus sinensis need full sun to light shade or very high interior lighting with a well drained soil mix. In the greenhouse, we use a soil mix consisting of 2 parts peat moss to 2 parts loam to 2 parts sand or perlite. Even though orange trees are fairly drought tolerant in the landscape, they do better if kept moist. In the hot summer, the trees are watered daily in the greenhouse and fertilized weekly with a balanced fertilizer. Since oranges bloom on new wood, any pruning should be done after the fruit ripens. During the winter, we keep the plants moist and never let the nighttime temperature fall below 55°F (13 C°).
Propagation: Citrus sinensis are propagated by seed and by grafting selected cultivars.
Citrus sinensis was featured as Plant of the Week May 6-13, 2005.
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 the late 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.