HOME FRUIT PRODUCTION-GRAPEFRUIT
Julian W. Sauls
Professor & Extension Horticulturist
Grapefruit apparently originated as a natural mutation of the shaddock or pummelo somewhere in the West Indies. It was first described in 1750 in Barbados, while the first record of the term grapefruit occurred in 1814 in Jamaica. Credit for its introduction to the United States in accorded to Count Odette Phillipe, a Spanish don, who planted it in Pinellas County, FL, about 1823. That grapefruit originated as mutation from pummelo seems more likely when one considers the number of grapefruit varieties today, most of which originated as mutations from existing grapefruit varieties.
While Charles Volz is credited with the first successful orange plantings on sour orange rootstock in the Lower Rio Grande Valley of Texas in 1908, little is known of the first plantings of grapefruit in Texas. The earliest record of grapefruit shipments from Texas was 120 tons during the 1919-20 season. Texas grapefruit production peaked at 960,000 tons during the 1945-46 season, which coincided with a peak U.S. production of 2,485,000 tons. That total U.S. production was not achieved again until 1971-72, but Texas grapefruit production has rarely exceeded half its peak level.
While the first grapefruit were white-fleshed and seedy, the Texas grapefruit industry ultimately developed around seedless, red-fleshed varieties, all of which arose in Texas by mutation from existing grapefruit.
Except during major freezes and the recovery from them, the Texas citrus industry annually produces more tonnage, about 80 percent of which is grapefruit, than all other tree fruits and nuts in Texas combined. Because of this and the quality and importance of Texas red seedless grapefruit, the Legislature in 1993 designated red grapefruit as the State Fruit of Texas.
Grapefruit achieves its best quality under conditions of hot days and warm to hot nights, which results in higher sugars and lower acids than grapefruit produced in the cooler night temperatures common in Arizona and California. It grows well in both tropical and subtropical climates of the world, but it is a little less cold hardy than oranges.
Mature, healthy grapefruit trees that are well-hardened by previous cool to cold weather can probably tolerate temperatures in the mid-20's without leaf or twig damage, although ice will form in the fruit of grapefruit after about 3 to 5 hours at 27. Because severe freezes kill grapefruit trees in the Lower Rio Grande Valley, successful home grapefruit production will sooner or later require cold protection measures.
SOILS AND SITE SELECTION
Grapefruit 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, grapefruit 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, grapefruit grows and produces best in full sun.
The major grapefruit varieties in Texas are 'Ruby Red', 'Henderson'/'Ray' and 'Rio Red'. All were discovered in Texas and all are red-fleshed, seedless and have varying degrees of redness in the peel.
'Ruby Red' was discovered as a limb sport ( a mutation of one limb which has different fruit characteristics than the rest of the tree) on a 'Pink Marsh' tree in 1929 by A. E. Henninger of McAllen, TX, who was granted a patent (U.S. Plant Patent No. 63) in 1934. The fruit is of excellent quality, seedless (i.e., 0 to 6 seeds), red-fleshed, oblate and thin skinned. The fruit usually has a red blush on an otherwise yellow peel. The interior color fades badly after the first of the year.
At least half a dozen other limb sports of 'Pink Marsh' were discovered in Texas between 1930 and 1940--all very similar to 'Ruby Red'--plus one limb sport from 'Foster' pink seedless grapefruit. For the most part, all are lumped together as 'Ruby Red' for commercial purposes.
'Henderson' and 'Ray' are usually lumped together in the industry as they are nearly indistinguishable. Both were discovered in the Valley in the early 1970's-- 'Henderson' as a limb sport on 'Ruby Red' and 'Ray' as four trees, the buds of which were supposed to be 'Ruby Red'. The fruit of these two varieties is similar to 'Ruby Red' in almost all respects except that the peel is more attractive than 'Ruby Red' and the flesh is even redder. While the flesh color also fades after mid-season, it retains some semblance of redness far longer than is the case with 'Ruby Red'. Three other similar limb sports of 'Ruby Red' were discovered in the 1970's by Texas growers, but none has achieved the prominence of 'Henderson'.
'Rio Red' was discovered in 1976 by R. A. Hensz as a limb sport on a tree being grown from 'Ruby Red' budwood that had been irradiated. Released in 1984, 'Rio Red' has interior color that is twice as red as 'Henderson' and its color persists throughout the season. 'Rio Red' has an overall reddish tinge on the peel and a lighter-colored halo in the flesh when viewed in cross-section. The biggest detriment of 'Rio Red' is that its basic shape is more spherical than oblate and sheepnosing of the stem end is a persistent problem.
Texas markets its 'Ruby Red' and 'Henderson'/'Ray' under the name Ruby-Sweet. Some 'Henderson' fruit are marketed as 'Flame' to distinguish it from 'Ruby Red' and to capitalize on Florida's 'Flame' grapefruit which is a nucellar 'Henderson' . 'Rio Red' is marketed under the name Rio Star.
Minor varieties in Texas include 'Duncan' which is the original white, seedy grapefruit variety and 'Marsh' white, seedless grapefruit. Some people consider the white-fleshed grapefruit to have better flavor than the pigmented varieties, but the grapefruit market obviously prefers the red-fleshed, seedless varieties. 'Garner Seedless' is a white grapefruit discovered near Laredo, TX, that created some excitement in the Winter Garden because of its apparent cold hardiness. Its hardiness, however, was due to the fact that it was propagated from seed and thereby grew on its on roots rather than having been budded or grafted onto rootstocks. Seedling citrus trees are generally somewhat more cold hardy than budded or grafted counterparts.
'Star Ruby' grapefruit is still popular with some home fruit growers and consumers, although its commercial tenure was rather short-lived. It was developed by R.A. Hensz from irradiated seed of the seedy, red-fleshed 'Hudson' grapefruit. Its flesh is the most intensely red of the Texas varieties; its peel and even the cambial layer of the wood have a pronounced reddish tinge. Its erratic and poor bearing habit, as well as its sensitivity to foot rot and to some commonly-used citrus herbicides doomed 'Star Ruby' to obscurity.
A seedy, orange-fleshed fruit that matures slightly earlier than grapefruit because of its lower acidity, is grown in a few home plantings in the Valley. It is known by various names, including 'New Zealand Grapefruit', and 'Poorman Orange'. The fruit and tree are very similar to grapefruit, but it is probably a pummelo hybrid that may have originated in China or Australia.
The following are varieties that are not available in Texas, to my knowledge, and are not likely to become available unless there is sufficient demand that they can be entered into the Texas Citrus Budwood Foundation for certification as being virus-free. They are described, however, because the author has received inquiries about them over the years.
'Burgundy' is a mutation from 'Pink Marsh' that was discovered in 1948 near Fort Pierce, FL and patented (U.S. Plant Patent No. 1276) in 1954. Its flesh is deeper red and more uniform than that of 'Ruby Red' and its color holds late into the season. That 'Burgundy' does not mature until April or May (in Florida) was a drawback to commercialization--but such late maturity may be advantageous for an extended season.
'Chironja' is an apparent grapefruit-orange hybrid that was discovered in Puerto Rico. The fruit is large and oblate like grapefruit, with peel and flesh color more like that of orange. Its flavor is pleasant, lacking the bitterness characteristic of grapefruit. It is grown to a limited extent in Puerto Rico, but not elsewhere.
'Oroblanco' is a patented hybrid between grapefruit and an acidless pummelo that was released by the University of California. It is sweet, without the bitterness of grapefruit, few-seeded and a little larger than a grapefruit. The rind is smooth, very thick and greenish yellow at full maturity, which is usually December to January in inland California and desert areas.
'Melogold', a sibling of 'Oroblanco', is somewhat larger with a thinner peel which is still considerably thicker than that of grapefruit. Its fruit are sweet, with a pummelo-like flavor, and few seeded. The rind is yellowish green at maturity, which is usually November to January in interior production areas of California and Arizona.
Neither 'Oroblanco' nor 'Melogold' have been tested nor are they available in Texas. The descriptions are based on California conditions in which they are grown; it would be expected that the rind would be thinner and less yellow under conditions in Texas.
Either T-budding or inverted T-budding onto sour orange seedling rootstocks is the primary means used to propagate grapefruit trees in Texas. Because of the high degree of nucellar embryony (seeds come true-to-type) in most grapefruit 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 several years until the seedling trees grow through juvenility and become capable of bearing.
PLANTING AND ESTABLISHMENT
Most grapefruit 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 grapefruit 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 grapefruit 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 grapefruit tree can be considered to be established.
All weeds and lawngrass should be completely eliminated inside the watering ring, as the developing grapefruit 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 citrus because it increases the possibility of the tree contracting foot rot, for which there is no cure. 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 grapefruit 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 grapefruit 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 grapefruit trees, if properly established and grown, should bear in the third season after transplanting. Any fruit that sets in the first and second years should be removed in order to direct all of the young tree's energy into growth. The first production could easily exceed 25 pounds per tree, which should increase to some 250 pounds or more by the tenth season.
Generally, grapefruit does not 'ripen" in the normal sense of the word, rather, it matures to good eating quality. Texas grapefruit will usually achieve legal maturity in mid-to-late October, although the peel color will likely still be quite green (plus the red blushing of red-fleshed varieties). Natural degreening occurs gradually through the next couple of months. The longer the fruit remains on tree, the larger it becomes and the sweeter it becomes. Grapefruit holds very well on the tree, so fruit can be harvested as needed from late October through May.
As stated previously, the interior flesh color of 'Ruby Red' fades rapidly after the first of the year, while that of 'Henderson' begins to fade rapidly in late February or March. 'Rio Red' retains its deep red color throughout the season.
Grapefruit is primarily eaten fresh but it is readily processed as well. The juice can be extracted and chilled for use within a couple of weeks; it can also be frozen for later use. In addition, the sections can be removed from cut halves (just as it you were eating a grapefruit half), placed in locking freezer bags and frozen for use during the summer and early fall until the next crop matures.
The pest and diseases which affect grapefruit 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 grapefruit should have 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 grapefruit 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 grapefruit 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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