Edible oranges are called sweet oranges, and ornamental oranges are called sour oranges. The Citrus Experiment Station at the University of California Riverside maintains and researches over 1,000 kinds of citrus trees. Some ornamental sour orange trees in their collection include bergamot, Bouquet de Fleurs and chinotto. Oil of bergamot is pressed from bergamot orange rinds and gives Earl Grey tea its distinctive flavor. Bouquet de Fleurs bears sweetly scented flowers that are used to make perfume. Chinotto orange, or myrtle-leaf orange, is a dwarf ornamental that shows beautifully in patio pots because its small orange fruits are profuse and long-lasting on the tree.
Ornamental orange trees bear fruit just as edible orange trees do, but they are primarily grown for their foliage, flowers, ornamental fruit color and smaller sizes. They make good patio plants for container culture or good landscape specimen or hedge plants. As common members in the Rue plant family, sharing the genus Citrus, ornamental orange trees are susceptible to the same pests as are edible orange trees, according to Purdue University.
Ornamental Orange Trees
Citrus Leafminer and Peelminer
The citrus leafminer is appropriately named because its larvae mine tunnels through citrus fruit leaves. The adult leafminer is a moth that lays eggs on the undersides of leaves. When larvae hatch, they begin tunneling through tender new-growth foliage and leave telltale trails of frass, or excrement. When larvae are ready to pupate, they emerge from leaf tunnels and roll leaf edges around themselves. Peelminer is also a citrus moth, but its larvae feed on fruit instead of leaves.
Citrus looper larvae are small worms that are the immature form of a moth. Adult female moths lay 100 eggs at a time, several times a year. Worms have legs at the fronts and backs of their bodies, but not in the middle. Their physical structure allows them a looping, or inching, mobility that gives them the common name of inchworm. Young looper larvae feed on tender leaf margins, and mature larvae consume entire leaves, flowers and fruit.
Citrus psyllids are dangerous orange pests because they act as vectors, or agents that transmit disease. Candidatus Liberibacter asiaticus causes yellow shoot disease, which may be “the most devastating citrus disease in the world,” according to the Florida Department of Agriculture and Consumer Services. The disease causes yellow shoots and green fruit that do not attain proper color. Inspecting nearby orange jasmine plants is a good way to scout for citrus psyllids. Orange jasmine is a common host plant for this pest and may harbor extensive populations that migrate to ornamental orange trees.
- Purdue University: Sour Orange
- University of California Riverside: Citrus Variety Collection
- University of California Agriculture and Natural Resources: Citrus Leafminer
- University of California Agriculture and Natural Resources: Citrus Loopers
- University of Florida – Southwest Florida Research and Education Center: Research – Asian Citrus Psyllid
- University of California Riverside: Bergamot Sour Orange Hybrid
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