With its southern border against the Gulf of Mexico, Louisiana has a climate that ranges from subtropical, hot, humid areas in its southern part to colder areas that regularly experience below-freezing winter temperatures in its northern section. The state's U.S. Department of Agriculture plant hardiness zones range from 8a to 10a. Sweet orange trees (Citrus sinensis) are hardy in USDA zones 9 through 11, suitable for growing in Louisiana's subtropical areas.
Louisiana Climate Zones
Louisiana features three climate areas, which differ from its USDA zones. Its first climate area, Climate Zone 1, is the southernmost and projects into the Gulf of Mexico. It is the best area for growing oranges and encompasses USDA zone 9b. Climate Zone 2, which extends north to a line drawn about from southern Beauregard Parish to northern Washington Parish, contains USDA zone 9a.
Sweet Orange Overview
Sweet oranges generally reach 20 to 30 feet tall and 15 to 20 feet wide. The evergreen trees have abundant, white, fragrant flowers in spring followed by round, green fruits that ripen through the summer months. Depending on a tree's variety, its fruits are ready to pick in fall and winter, sometimes into spring. Certain orange tree varieties withstand occasional cold better than other varieties. Select varieties grafted onto disease-resistant, cold-hardy rootstocks such as hardy orange (Poncirus trifoliata), which is hardy in USDA zones 5 through 9. Hardy orange is considered invasive in some U.S. locations when grown as a regular tree rather than used as a rootstock.
Probably the most commonly planted sweet orange worldwide, "Valencia" (Citrus sinensis "Valencia") is late-maturing, with fruits ready for harvest in April. The fruits are still maturing when periods of freezing weather are most likely to occur in southern Louisiana during December and January. Orange trees suffer heavy fruit drop when exposed to temperatures below 32 degrees Fahrenheit. "Valencia" grows best in Louisiana in the extreme southern part of Climate Zone 1.
"Washington Navel" (Citrus sinensis "Washington Navel") produces fruits that ripen in November and December, and it grows in Climate Zone 1 and the southern part of Climate Zone 2 in Louisiana. Its seedless fruits have a thin skin, a navel structure at the end, high sugar content and a flavor considered good. Some other navel orange varieties tried in Louisiana include "Dream," "Fisher" and "Carter," which bear more heavily than "Washington Navel." All are Citrus sinensis varieties.
Varieties with Numerous Seeds
The traditional variety of sweet orange in southern Louisiana, "Louisiana Sweet" (Citrus sinensis "Louisiana Sweet") matures in December, producing flavorful, medium to large fruits with numerous seeds on thorny trees. Grow it in Louisiana's Climate Zone 1 and the southern part of Climate Zone 2. Also harvested in December, "Pineapple Sweet" (Citrus sinensis "Pineapple Sweet") has seedy fruits that resemble pineapple in taste. It grows best in Climate Zone 1.
Varieties with Few Seeds
An early variety that matures in December, "Hamlin" (Citrus sinensis "Hamlin") has fruits with a mild, sweet flavor and not many seeds. It grows best in Louisiana's Climate Zone 1. Also for Climate Zone 1, "Plaquemines" has medium-size, seedless fruit that are low in acid. Those fruits mature in January.
Orange trees need full sun and tolerate a variety of well-draining soil types. Because southern Louisiana experiences average rainfall amounts about 64 inches per year, watering needs are less than in drier citrus-growing areas. Pay close attention to newly planted trees, and water their soil frequently if needed. In general, water the young trees thoroughly if two weeks pass in spring or summer without at least 1 inch of rain. If the top 1 to 2 inches of soil of established trees become dry, water the trees thoroughly. Provide each orange tree with an area about 30 to 40 feet in diameter. Space every tree at least 15 to 20 feet on all sides from buildings and other trees.
Fertilizer needs vary with the age of orange trees. Louisiana State University Extension recommends giving each newly planted tree 1/2 pound of 8-8-8 in mid-March, or when it produces new growth. From years 2 to 12, an orange tree should receive 1 to 1 1/2 pounds of 8-8-8 for every year of the tree's age in late January or early February. An older tree should receive no more fertilizer than a 12-year-old tree. Scatter the fertilizer evenly under each tree, keeping it away from the trunk, and gently incorporate it into the top layer of soil, avoiding disturbing the roots. Water the fertilized soil thoroughly.
Be prepared to protect orange trees from temperatures 32 degrees and lower. For mild freezes, cover the trees with frost blankets or sheets. Hold the coverings off the leaves with a frame. Include an electric light bulb under each covering during cold freezes. During severe cold, wrap each tree trunk with tree wrap, protecting the area where the top part of the tree is grafted onto the rootstock. Minimize freeze damage by not pruning or fertilizing the orange trees in late summer or fall because pruning encourages new growth, which can be damaged by cold.
- Louisiana Tech University: Climate of Louisiana
- Louisiana State University Agricultural Center, Research and Extension: Louisiana Home Citrus Production
- U.S. Department of Agriculture: Plant Hardiness Zone Map
- Floridata: Citrus Sinensis
- Regional Integrated Pest Management Centers: Crop Profile for Citrus in Louisiana
- Missouri Botanical Garden: Poncirus Trifoliata
- Four Winds Growers: Problem Solver -- How Often Should I Water?
- Photo Credit richterfoto/iStock/Getty Images
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