HOME FRUIT PRODUCTION-ORANGES
Julian W. Sauls, Ph.D.
Professor & Extension Horticulturist
Texas Cooperative Extension
Sweet oranges, which are native to northeastern India, are the most widely grown species of citrus. They spread rapidly along trade routes between Asia, Europe and Africa, so little is known of their actual introduction to Europe. Columbus reportedly established a planting in Hispaniola on his second voyage in 1493. Spanish explorers introduced oranges throughout the New World, including to Florida when they founded San Augustine in 1565. While Texas is noted for its red grapefruit, orange trees are common throughout areas of the state where citrus can be grown.
Oranges are grown throughout the world in tropical and subtropical areas, but they achieve the best quality under subtropical conditions. For the most part, the warm, humid conditions of south Texas produce a thin-skinned, yellowish orange fruit with yellowish orange flesh that is quite sweet and juicy. By contrast, cooler climates such as California and Arizona produce fruit having brightly colored, thick, peel and orange flesh.
Mature, healthy orange trees that are well-hardened by exposure to previous cool weather can tolerate temperatures in the middle to low 20's without leaf or twig damage, but ice will form in the fruit after 3 to 5 hours at or below 27. Severe freezes, however, do kill orange trees in south Texas, so long-term success will sooner or later require cold protection measures.
SOILS AND SITE SELECTION
Orange trees on sour orange rootstock are well-adapted to deep, well-drained soils. Loamy soils are preferred while heavy clays and poorly-drained soils will result in poor growth and production as well as shorter life.
For maximum cold protection, oranges in the home landscape should be planted on the south or southeast side of the house. Distance from the house or other buildings and driveways or walkways should be at least 12 feet to allow adequate room for the tree to grow to its mature size. While large, overhanging shade trees will provide some cold protection, orange trees grow and produce best in full sun.
Sweet oranges are generally classified as round oranges, navel oranges, pigmented or blood oranges and acidless oranges. Too, they are classified as seedy or seedless (0-9 in Texas) and by season of maturity. Early season oranges mature in September or October. Mid-season oranges mature in late November to early January, and late season oranges mature in February or March.
Most of the world's orange production is the round oranges, all of which are rather difficult to peel. Navel oranges are characterized by the presence of a secondary fruit embedded in the blossom end of the fruit, creating a "navel" opening. The navel can be small and almost inconspicuous to large and protuberant. Navel oranges are fairly easy to peel and are the premier orange for eating out-of-hand.
Blood oranges contain red anthocyanin pigments in the flesh, but the pigmentation requires cool night temperatures to develop. In Texas, few of the blood oranges have more than a few flecks of pigment. The acidless oranges are insipid and of poor quality; no varieties are grown in Texas.
Round orange varieties in Texas comprise about 7,000 acres in commercial production. 'Parson Brown' originated as a chance seedling at the home of Reverend N.L. Brown near Webster, FL, in 1865. Its fruit are round, medium large, has a thick, pebbly peel and contains 10-20 seeds. It usually matures in early September in the Valley. Both peel and juice color are poor, as is juice quality.
'Hamlin' originated as a chance seedling in an orchard planted in 1879 near Deland, FL. Its fruit are round, small to medium, commercially seedless (0-6 seeds) and has a smooth, thin peel. Both peel and juice color are poor. It matures in late September in the Valley.
'Marrs' arose as a limb sport of 'Washington' navel in 1927 in Donna, TX. The tree is small by comparison to other oranges. Its fruit are medium large, round to slightly oblate, with a thin, smooth, moderately thick peel that is easily bruised during harvest. It can contain as many as nine seeds. The peel is yellowish, as is the juice, but quality is not particularly good because of low acidity, although the flavor is sweet. It matures in late September.
'Pineapple' orange originated from seedlings planted about 1860 near Citra, FL. Its fruit are medium large, somewhat flattened on both ends, with a moderately thick, smooth peel that develops good orange color under cool night conditions. Juice color and quality are very good. It usually contains 15-25 seeds. 'Pineapple' matures about Thanksgiving in the Valley. Unfortunately, the name 'Pineapple' has been used in Texas to designate seedy oranges, which includes both 'Parson Brown' and true 'Pineapple' orange. Basically, if the orange in question matures well before Thanksgiving, it isn't 'Pineapple'.
'Jaffa' was introduced to Florida in 1883 from Palestine, but it does not appear to be quite the same as the original variety. Its fruit are small to medium, commercially seedless, with a thin, smooth peel. Peel color is yellow as is juice color. The flesh is melting in texture and of very high quality, producing a thick, nectar-like juice. 'Jaffa' usually achieves maturity in the Valley about Christmas. By some accounts, 'Jaffa' in Texas may be better described as Palestine Jaffa Blood Orange, as flecks of pigment often occur in the fruit during cooler winter conditions in the Valley.
'Valencia' orange is the most widely planted orange variety in the world. It originated in either Spain or Portugal, but no one knows which. It was introduced to Florida in 1870. 'Valencia' fruit are medium large, commercially seedless, with a moderately thick peel. It is usually slightly oblong in shape. Peel color, juice color and eating or juice quality are excellent, setting the standards to which other round oranges are compared. It matures in early February and holds well on-tree into the summer. Fruit will regreen at the time of the spring growth flush.
Navel oranges supposedly originated in the Mediterranean area from which they were taken to Brazil. They were introduced by the U.S.D.A. to the United States from Brazil in 1873. A number of varieties have been tested in the Valley, but there has been little advantage of one over another. 'Washington' is a large, oblong fruit with a protuberant navel that is considered parent to most other navel oranges. 'Thompson' is similar to 'Washington', as are 'Atwood', 'Fisher', 'Summerfield', 'Texas' and a number of others which originated from 'Washington'.
The two most widely planted navel orange varieties in Texas are 'Everhard' and 'N33E'. 'Everhard' is similar to the 'Baianinha Piracicaba' of Brazil, having rather smaller fruit that are oval to round. The navel is very small and closed, commonly being inconspicuous or absent altogether. The fruit is thin skinned, of very good flavor, and it reaches maturity in late September.
'N33E' is a local selection which was discovered as a limb sport of 'Marrs' orange in the late 1960's near Edinburg, TX. While the fruit is similar to 'Washington' navel, the trees are more productive and more consistent than 'Washington'. In some years, 'N33E' suffers extensive fruit splitting in August-September, yet production still remains high.
The blood oranges are similar to round oranges in their growth and appearance, the exceptions being in internal flesh characteristics. The flavor of blood oranges is rich and sprightly. There are a few blood oranges in Texas, including both highly colored types and those with only flecked coloration in the flesh. Even the highly colored types in Texas do not develop the dark red coloration for which the blood oranges are noted. 'Moro' and 'Sanguinelli' are usually seedless and develop the most intense color, while 'Ruby' is lightly flecked at best, with 10-15 seeds. 'Ruby' and 'Moro' are considered mid-season, while 'Sanguinelli' is late season.
Other citrus varieties, that are called "oranges", such as 'Temple' and 'Ambersweet', are actually hybrids and are discussed in Home Fruit Production--Mandarins.
Either T-budding or inverted T-budding onto sour orange seedling rootstocks is the primary means used to propagate oranges in Texas. Because of the high degree of nucellar embryony (seeds come true-to-type) in most orange varieties, they can be grown from seed. However, seedage has two major drawbacks: 1) the seedling-grown trees will be short-lived because of their susceptibility to Phytophthora disease (both foot rot and root rot) and 2) fruit production will usually be delayed for up to 15 years until the seedling trees grow through juvenility and become capable of bearing.
PLANTING AND ESTABLISHMENT
Most orange trees propagated in the Lower Rio Grande Valley are grown in field nurseries. Such trees are then dug as if they will be balled-and-burlapped, but instead of wrapping the root ball with burlap, nurserymen commonly use a strip of burlap under the tree to lift it into a two-gallon container. Since the root ball is intact and includes the soil in which it was growing, such trees can be transplanted directly from the container.
Some orange trees, however, are container-grown entirely in an artificial, soilless medium--which requires special treatment at transplanting. After the planting hole is ready, remove the tree from the container and use a gentle stream of water from the garden hose to wash an inch or so of the medium from all around the root ball, thereby exposing the peripheral roots. Thus, the outer roots are placed in contact with the soil of the planting site and growth commences almost immediately.
Under no circumstances should soil around the proposed planting site be removed to form a shallow basin for watering--to do so almost guarantees that the young tree will contract foot rot and die before its fifth year. The soil in the planting site should be at least as high as the surrounding yard, if not higher. In addition, the tree should be set slightly higher than it was in the nursery container to assure that the budunion will remain well above the soil.
Mixing topsoil, compost, peat or other materials with the backfill soil is neither necessary nor desirable in good soils. Set the tree in the hole, backfill about halfway, then water sufficiently to settle the backfill around the lower roots. Finish backfilling the hole and then cover the root ball with about in inch of soil to seal the growing medium from direct contact with the air and thereby prevent rapid drying of the root ball.
To facilitate watering, bring soil from the garden or elsewhere to construct a watering ring atop the ground around the newly planted tree. The ring should be about two feet across and several inches high and thick. To water, just fill the water ring immediately after planting. After the water soaks in, it may be necessary to add a little soil to any holes formed as the soil settled around the roots.
The watering interval should be every few days for the first couple of weeks, then gradually increased to 7 to 10 days over the next couple of months. The watering ring will gradually melt into the surrounding soil, at which time the young orange tree can be considered to be established.
All weeds and lawngrass should be completely eliminated inside the watering ring, as the developing tree cannot compete well. A systemic, contact herbicide will work very well, so long as it is not allowed to contact the young tree leaves or green bark.
The best way to protect the young trunk from herbicide damage and, at the same time, to prevent sprouts along the trunk is to crimp an 8-inch by 18-inch piece of heavy duty aluminum foil around the trunk from the ground to the scaffold limbs. Fold the foil lengthwise, bring the long edges past the trunk on both sides, crimp the two edges together and lightly squeeze the foil around the trunk.
While mulching of citrus trees is commonly practiced in southeast Texas where there is an abundance of materials to use, mulching is not recommended for oranges because it increases the possibility of the tree contracting foot rot, for which there is no cure for home gardens. If you insist on mulching, keep the mulch at least a foot away from the trunk.
Fertilizer should be withheld until after growth commences. During the first year, a single cupful of ammonium sulfate (21-0-0) split into three or four applications is adequate. Use two cups in the second year and three in the third. Just scatter the fertilizer on the ground around the tree and water thoroughly. In areas other than the Valley, use whatever fertilizer analysis that is in general use in the area for trees and shrubs--simply adjust the rate based upon nitrogen content.
Cold protection measures for orange trees will be required sooner or later. Soil banks are very effective for young trees; the soil should be put up about Thanksgiving and left in place until early March. Exercise care when taking down the soil bank, as the bark underneath will be extremely tender.
Blankets, tarps or similar covers are also very effective and have the advantage of being quickly draped over the young tree. The corners should be stretched outward and tied down. More elaborate protection can be provided by erecting a frame structure of wood or PVC pipe over the plant to facilitate the use of plastic or large tarps during particularly severe cold weather. Supplemental heat can also be provided under the covers; incandescent bulbs and heat lamps are useful.
MATURE TREE CARE
Watering should be slow and thorough; probably every couple of weeks would suffice in any but the very sandy soils. Nutrition should continue at about one cup of ammonium sulfate per year of tree age annually in split applications in February, May and September, i.e. a 6-year-old tree should receive about six cups of 21-0-0 for the year. Adjust the rate for other fertilizers based upon the relative nitrogen content.
Lawngrass should be kept back about a foot from the canopy of the tree. Other than cold damage, no pruning should be necessary, as the orange tree will develop its natural shape without pruning. While mulching is not recommended for citrus trees, if you must mulch, keep the mulch at least one foot away from the tree trunk.
PRODUCTION, MATURITY AND USE
Budded orange trees, if properly planted and grown, will bear harvestable fruit in the third season after transplanting. Any fruit that might set in the first and second seasons should probably be removed so that all of the young tree's energy is directed into growth.
Production of navel oranges could approach 10-15 pounds in the third season, increasing to around 100-150 pounds at full maturity in the tenth season. Early and midseason oranges could start at about 20-25 pounds in the third season and increase to around 200-250 pounds per tree by the tenth season. 'Valencia' orange production will be a little less than that of early oranges.
Oranges do not "ripen" in the general sense of the word as it is applied to other fruits; instead, they mature to good eating quality. Too, peel color is no indicator of maturity, as the peel undergoes natural degreening in November and December, and peel color of 'Valencia' oranges often regreens after the spring growth flush occurs.
Oranges are classified by their season of maturity, i.e., early, midseason and late oranges. Early oranges include 'Parson Brown', 'Marrs', navels and 'Hamlin', in order of maturity from early September through early October. Midseason oranges include true 'Pineapple' and 'Jaffa', with 'Pineapple' usually maturing about Thanksgiving and 'Jaffa' about Christmas. The only late orange in Texas is 'Valencia' which matures about early February.
Most oranges do not hold well on-tree; as they become overmature, they soften and drop. Overmature navel oranges also begin to dry out on the stem end, especially the larger, more oblong fruit. 'Marrs' and navels may hold into early February, especially in seasons having fairly cool weather in December and January. Midseason oranges typically hold through late February to March. 'Valencia' oranges hold much better than other oranges, often into June or July. Within limits, the longer the fruit stays on the tree, the sweeter it becomes.
Navel oranges are typically peeled and eaten out-of-hand, the others are more commonly sliced or sectioned for fresh consumption or juiced for drinking. Seedy varieties are often referred to as "juice oranges" since juicing is about the easiest means to remove the seeds. Navel oranges can be juiced for immediate consumption, but navel orange juice becomes bitter after a few hours. With the exception of navel, the other oranges can be sectioned for freezing and the juice can also be frozen for later use.
The pest and diseases which affect oranges in Texas are detailed in Home Fruit Production-Citrus, Table 2. In addition, the Asian citrus leafminer attacks the new flushes of growth when the developing leaves are only about an inch long, leaving serpentine trails from their feeding and causing stunting and distortion of the leaf. Occasionally, trails or mines occur on fruit as well. Each growth flush is susceptible to attack and there will be four growth flushes annually. The spring flush is least damaged, since the leafminer does not overwinter well, but the later flushes can be devastated.
There are no chemical controls available for home use, although citrus spray oils do deter infestation if the application is timed to the development of a new flush of growth. Otherwise, it is best to try to ignore the damage; leafminer will not kill the tree and indiscriminate spraying kills a lot of the natural predators and parasites that help to keep leafminer populations down.
There are very few orange tree problems that are life-threatening--and the home gardener cannot do anything about those anyway. Many of the rest of the insects and diseases that afflict oranges can generally be ignored in the home garden, as blemishes to the peel affect only the appearance and, in some cases, size of the fruit.
If one must spray, first identify the problem, then select the appropriate material and apply it properly and at the appropriate time to control the pest while minimizing damage to the complex of beneficial organisms that exist in citrus.
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This page revised July 26, 2005