Citrus sinensis, or sweet orange, is the most widely grown citrus fruit. Varieties include navel, valencia, and blood oranges. It is an attractive, evergreen tree that does best in subtropical climates, producing fragrant white flowers in spring with the fruit maturing in the fall or winter. It will usually attain a height between 20 and 30 feet.
Choose a sunny location on the south or southeastern side of your home at least 12 feet from the building and driveway for the best fruit production. This will give the tree some protection from wind and freezing temperatures. Citrus sinensis can be planted in partial shade but will produce less fruit. The soil must be well draining, because citrus will not tolerate wet feet.
Plant the young tree at the same level, or slightly higher, than it was planted in its container. Citrus sinensis is grafted onto sour orange root stock and the bud union must remain above the soil line. The bud union can be recognized by a bulge or a diagonal scar on the lower trunk. The planting hole should be twice the size of the root ball. Work some organic material, such as manure, or compost into the planting hole, but do not add fertilizer. In heavy soils adding sand will improve drainage.
Apply a nitrogen-rich fertilizer when new growth appears. Oranges are heavy feeders and should be fed three times a year. Applications should coincide with the first flush of green growth, again when the flowers bud, and once in early summer. If you regularly apply nitrogen fertilizer to your lawn, there may be no need for additional fertilizer applications. Orange leaves should be bright green and shiny. If they look a little pale, your plant needs to be fed.
Water your tree deeply once a week until established. Then water deeply once every 10 days, more frequently during prolonged dry weather. Orange trees are drought tolerant but the fruit will be smaller in size and not as juicy. Mulching is not recommended due to the trees' susceptibility to foot rot. If you do mulch, keep the material at least 1 foot away from the trunk.
Remove any dead or damaged branches, and any shoots that emerge below the bud union. An occasional pruning to promote good air circulation will help suppress fungus diseases.
Identify pests before applying pesticides. Orange trees are quite hardy and can withstand some damage. Prevention is a better solution. Remove plant debris from under the tree and promote good air circulation.
Water your tree thoroughly when freezing temperatures are expected. Small trees can be covered with blankets. Orange trees can survive temperatures as low as 25 degrees Fahrenheit if there have been several days of cool weather before freezing temperatures arrive. Damage to blossoms will result in a smaller crop and can occur when temperatures fall below 35 degrees Fahrenheit.