ANR-603

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Citrus for Southernand Coastal Alabama

With proper attention given to selection of themore cold hardy varieties, along with recom-

mended care, citrus fruits can be successfullygrown around homes in the coastal and extremesouthern areas of Alabama. Citrus plants are veryversatile around the home and can be used as indi-vidual specimen trees, hedges, or container plants.Their natural beauty and ripe fruits make them veryattractive additions to the South Alabama homescene.

The most significant limiting factor to citrus cul-ture in these areas is damage from low winter tem-perature. The brief history of citrus culture in theUnited States given below vividly illustrates thedevastating effect of winter freezes.

Historical Background of Citrus in the United States

Citrus was first introduced into the continentalUnited States by the early Spanish explorers atSaint Augustine, Florida, in 1565. Considerable timeelapsed before citrus was introduced into Arizona(1707) and California (1769).

History also indicates that citrus plants havebeen grown in gardens for many years in statesthat border the Gulf of Mexico and even as farnorth as Charleston, South Carolina. Small satsumaplantings developed in the Gulf states as early asthe 1890s. The freezes of 1894–95 and 1899 largelydestroyed this early attempt.

Plantings again resumed until the freeze of1916–17 struck, killing thousands of acres of citruscrops. By the early 1940s, the hardy satsuma hadagain made a comeback, when some 12,000 acresof plants were growing in the Gulf Coast areas ofLouisiana, Alabama, and northern Florida. Butfreezes in the two decades following World War IIall but eliminated these plantings. The only com-mercial citrus remaining in these areas (about 1,000acres) is located in the delta area south of NewOrleans.

Alabama now has a small but emerging com-mercial satsuma industry in the Mobile Bay area.

Selecting VarietiesThe three general classes of citrus that produce

sweet fruits are mandarins, sweet oranges, andgrapefruit. All of these citrus types develop into at-tractive medium- to large-size trees. However, someare better adapted to coastal Alabama conditionsthan others.

If the producer grows citrus “outside’’ in SouthAlabama and wishes to harvest the fruit, varietiesshould be selected that can be harvested early(September through November). Beginning inDecember (sometimes late November), freezingtemperatures are often severe enough to freezefruits while not damaging the trees. Freeze protec-tion methods available to producers may be inade-quate to keep fruit from freezing during December.Table 1 lists season of ripening along with seedcontent and pollination characteristics for a numberof citrus varieties.

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Table 1. Characteristics of Citrus Varieties

Fruit Type Harvest Seasona Seeds Per Fruitd Fruiting Behaviore

SWEET FRUITSatsumaArmstrong Early extremely early very few self-fruitfulBrown’s Select very early very few self-fruitfulPort Neches very early essentially none self-fruitfulOwari early very few self-fruitfulKimbrough early very few self-fruitfulTangerineClementineb early few to many cross-pollinationPonkan early midseason few to many self-fruitfulDancy midseason few to many self-fruitfulTangerine HybridsTangelos—Orlandob early midseason varies cross-pollinationOther Tangerine hybridsRobinsonb very early varies cross-pollinationSunburst very early varies cross-pollinationLee early varies self-fruitfulNova early midseason varies cross-pollinationPage early midseason varies cross-pollinationOsceola midseason varies cross-pollinationSweet OrangeNavel—Washington early very few self-fruitfulNavel-Cara Cara early very few self-fruitful(blood orange)Hamlin early few self-fruitfulAmbersweet early very few self-fruitfulGrapefruitDuncan early midseason many self-fruitfulTriumph early midseason many self-fruitfulRoyal midseason many self-fruitfulRedblush (Ruby) midseason few self-fruitfulThompson midseason few self-fruitfulStar Ruby midseason few self-fruitfulRay Ruby midseason few self-fruitfulRio Red midseason few self-fruitfulMarsh late midseason few self-fruitfulACID FRUITc

KumquatNagami early midseason few self-fruitfulMarumi early midseason few self-fruitfulMeiwa early midseason few self-fruitful

Calamondin all year few self-fruitfulLemon mostly early, someMeyer all year very few self-fruitful

LimeKey (Mexican) early midseason few to many self-fruitfulPersian early midseason essentially none self-fruitfulLime Hybrids

Eustis all year few self-fruitfulLakeland all year few self-fruitfulTavares all year few self-fruitful

aHarvest seasons are as follows: early (September to November); midseason (December to January), and late (February to June).bThese varieties can be interplanted to ensure cross-pollination, which usually results in larger fruit with more seeds and highertree yields.cAcid-type fruits may have fruits all year but produce the largest crop from the spring bloom.dCitrus fruits that have five to six seeds or fewer are considered “commercially seedless.” Selections above listed with “few” or “veryfew” are considered seedless.eIf self-fruitful, the variety can be planted by itself; if cross-pollination is indicated, a second variety must be used with this varietyfor best fruiting.

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MandarinsThe mandarin class includes a large group of

loose-skinned, deeply colored, highly flavoredfruits. They are sometimes referred to as the kid-glove (easily peeled) fruits. Within this group arethe mandarins, satsumas, tangerines, and tangerinehybrids. The terms mandarin and tangerine areused interchangeably for a number of loose-skinned fruits, depending on where they aregrown. For example, the Dancy variety is called atangerine in Florida and a mandarin in California.Unlike other types of citrus, cross-pollination is re-quired for optimum fruiting of a number of man-darin (tangerine) varieties and hybrids.

SatsumaThe highest degree of success and greatest sat-

isfaction in growing citrus in Alabama will be real-ized with satsumas. They withstand colder tempera-tures than the other forms of edible sweet citrus,produce more consistent crops over a longer peri-od of time, and require less cold protection.

Satsuma is a mandarin. It has excellent coldhardiness and ripens its fruit well ahead of mostfreeze problems (September to November). Owariis the most popular variety and is generally avail-able at retail outlets. Kimbrough is a recent releasefrom Louisiana, but it does not seem to be superiorto Owari. Brown’s Select is a very recent introduc-tion from Louisiana that is somewhat similar toOwari in tree and fruit characteristics but ripens itsfruit at least 2 to 3 weeks earlier. Overall, Brown’sSelect shows real promise and is being planted ex-tensively in Louisiana and Alabama. ArmstrongEarly (also called Early Armstrong) is an old varietythat has been grown for many years and is plantedto a small degree. Fruit of this variety ripen ex-tremely early (beginning in September), but thequality is not as good as later ripening selectionssuch as Owari. Port Neches, a recent variety intro-duced from Texas, ripens at the same time as andhas general characteristics similar to Brown’s Select.It provides yet another promising variety thatripens before Owari.

When grown under warmer climatic conditions(such as Florida), fruit often retain their peak quali-ty for not much longer than 2 to 4 weeks, afterwhich they may become puffy and rough in ap-pearance and lose flavor and juice content.However, under the cooler climatic conditions ofthe South Alabama area, fruits tend to remain ingood condition on the tree, retaining their juiceand flavor for 1 to 2 months or longer after reach-ing full maturity.

Satsumas may become fully ripened for eatingwhile peel color is still rather green. And certainfruits will ripen ahead of others. By beginning toharvest when the first few fruits become ripe,growers can lengthen the harvesting period by atleast 1 to 2 weeks.

For commercial purposes, however, it is usuallydesirable to wait until at least a prominent orangecolor has developed on the greenish peel (rind).

Tangerines (Mandarin)The next best type of citrus to plant from the

standpoint of cropping and cold hardiness is thetangerine. Because of their earlier ripening, satsumaand some tangerine fruit will escape damage frommany freezes that will severely damage midseasonvarieties of grapefruit and sweet oranges.

Dancy and Ponkan are exceptionally good tan-gerine varieties that produce quality fruits.However, their fruits may not develop good flavorbefore early to mid-December, which means fruitsmay be exposed to freezing temperatures before at-taining optimum ripeness. The Ponkan variety re-portedly is less cold resistant than most mandarins;fruits lose quality and the rind puffs if not pickedwhen ripe. Earlier ripening selections such asClementine (Algerian) tangerine should be plantedwhere possible. Sunburst was recently introducedby the USDA and is being grown extensively inFlorida. It ripens very early and has reasonablygood quality. Dancy, Ponkan, and Sunburst areself-fruitful, but Clementine requires cross-pollina-tion from another tangerine or tangerine hybrid.The tangerine hybrids described below providesome exceptionally good early maturing varietiesthat should be of interest to the homeowner.

The Dancy variety is susceptible to a new dis-ease (alternaria) and is being replaced in Florida.Its best flavor is in January, which means fruit arelikely to be injured by cold. Ponkan is not gooduntil December, and then for only a short period.

Tangerine HybridsTangelos are tangerine-grapefruit hybrids that

produce loose-skinned, tangerinelike fruits. TheOrlando variety is an ideal selection for homeown-er use. It is cold hardy and produces excellentquality fruits that ripen early (October toDecember). Dancy, Clementine, or some other vari-ety should be planted with Orlando for cross-polli-nation. If a second variety is not planted withOrlando tangelo, fruiting can be enhanced by scor-ing the trunk with a knife (cut through bark towood but do not remove any bark) or spraying thetree with 10 to 20 parts per million (ppm) of gib-

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berellic acid during flowering. Other early season(October to November) tangerine hybrids thatcould be grown include Lee, Robinson, Osecola,Nova, and Page. These will not cross-pollinate eachother. All of these hybrids (except Lee), requirecross-pollination for best fruiting. Lee does not re-quire cross-pollination as earlier reported but maynot be cold hardy enough for Alabama. Fruitingthese cross-incompatible varieties can be a prob-lem.

Sweet OrangesThis citrus can be grown along the lower

coastal area with a fair degree of success if ade-quate cold protection is provided each year.However, hard freezes (20°F and lower) will se-verely damage trees (fruit is damaged at 26° to28°F or colder). Hamlin may well be the best or-ange variety for Alabama (for fresh fruit and forjuice). Fruits are commercially seedless (6 or fewerseeds per fruit) and ripen early (October toNovember). The cold hardiness of Hamlin is equalto or superior to other sweet orange varieties. Allnon-navel sweet oranges are self-fruitful.

Ambersweet is the latest (1990) in a number ofcitrus hybrids released by USDA in Florida. This vari-ety (tangerine x sweet orange cross) has been classi-fied as an orange for marketing purposes. It is cur-rently one of the most sought-after varieties inFlorida. It possesses good cold hardiness (somewhatbetter than most sweet oranges but is still vulnerableto freezes) and ripens in early season (with Hamlin).Ambersweet is suggested as a new variety for thoseinterested in trying to grow sweet oranges.

The navel orange is recommended to thehomeowner who wants to raise seedless fruit for

eating fresh. However, navel oranges often producelight crops and are generally not as fruitful as regu-lar sweet orange varieties (non-navel types) such asHamlin. The Washington variety is recommended.Another variety of navel orange of interest to someis Cara Cara. It is similar to the Washington varietybut has red flesh. Dream and Summerfield shouldnot be used because of virus problems. Navelsmake a mediocre dooryard tree, even in Florida.Fruits sometimes begin drying out internally beforereaching full maturity. All ripen their fruits relativelyearly (October to December).

GrapefruitBecause of a lack of outstanding cold hardi-

ness, grapefruit will need cold protection morethan oranges. Although numerous selections areavailable, the Marsh (white seedless) and Redblushor Ruby (red seedless) varieties are the most fre-quently planted. Both produce excellent-qualityfruit and have few or no seeds. Royal and Triumphare lower in acidity, although not necessarily ofbetter quality. Marsh and Redblush are quite acidbecause of Alabama’s colder winters. Fruits ofMarsh or Ruby can be harvested as early as lateSeptember and October, but, if allowed to remainon trees until November and December, eatingquality significantly improves. The Star variety lackscold hardiness. All of these varieties are self-fruitful.

Several grapefruit varieties have been introducedduring the past 20 years from Texas. Among theseare the Star Ruby, Ray Ruby, and, most recently, theRio Red (discovered as a limb sport on Ruby Red).Producers who wish to try some of the newer grape-fruit selections may want to plant one or more ofthese varieties (all self-fruitful). However, thesevarieties are probably not very cold hardy.

Acid-Type Citrus FruitsThere are a number of hardy acid-type fruits

available for homeowner use. These plants makeattractive ornamental specimens and provide de-lightful fruits as well. All are self-fruitful, requiringno cross-pollination.

KumquatsThe kumquat tree (not the fruit) is the most

cold hardy of the commonly grown acid citrusfruits (it withstands temperatures of 15°F to 17°F).It resumes growth late in the spring, which helpsprevent late freeze damage. The kumquat is one ofthe most widely used citrus plants around thehome; it develops into an attractive shrublike treethat bears small orangelike fruit about 1 inch in di-ameter. Fruits can be eaten fresh, peel and all, or

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used in making jellies, marmalade, or candies.Several varieties are available, but only three arecommonly propagated: Nagami, Marumi, andMeiwa. Nagami fruit are oblong to date-shaped andhave acid pulp; the others are sweeter and rounder.Meiwa, which produces nearly round, sweet fruit,has become one of the most popular for homeplantings.

CalamondinsThe small, round fruit called calamondins look

somewhat like a tangerine and have very acid pulp.It makes an attractive plant for use around the homeas well as an indoor or container plant. Fruits arebeautifully yellow to orange in color and are readilyused as a substitute for limes and lemons. The treehas good cold hardiness (hardy to the low 20s).

LemonsMeyer is the most cold hardy variety of lemon.

The fruit ripening period usually lasts for severalmonths beginning in late summer. Good crops oflarge, practically seedless, juicy lemons are pro-duced. Plants developed from cuttings are oftenused around the home. Inherent cold hardiness ofthe tree approximates that of the sweet orange(mid-20s), except that the tree grows low to theground where temperatures are colder.

Lisbon, Villafranca, and Eureka, the commercialvarieties of lemon commonly produced inCalifornia, can be satisfactorily grown in containers.Ponderosa, a minor variety grown in Florida that

produces exceedingly large fruits, can also begrown as a container plant.

Lime HybridsThe Eustis limequat is a cold hardy lime-kumquat

hybrid that makes a very attractive small plant. It ispopular as a container plant. Limequats produce fruitresembling the lime in appearance and quality andmay serve as an excellent lime substitute. Cold hardi-ness is about equivalent to the tangerine (low 20s).Lakeland and Tavares are two less-popular varietiesoccasionally found in retail outlets. Fruits tend to beespecially sensitive to cold injury.

LimesLimes are among the most cold-sensitive of the

common citrus fruits grown. However, the Mexican(also called Key or West Indian) lime, famous forthe Key lime pie, can be grown as a containerplant when provided with inside protection duringthe winter. The Persian lime commonly grown inFlorida can also be used as a container plant.

Kaffir lime (Citrus hystrix) is a rather unusualselection that Asians think has medicinal properties.The leaves are used in preparing foods. Fruits aresmall and green, with a rough, wrinkled appear-ance. They have a slightly off-bitter flavor but maybe used in tea. This selection makes a very attrac-tive and satisfactory container plant.

Rootstock SelectionSelection of rootstock is another factor to be

considered. Scions* must be free of exocortis virus.Trifoliate orange (Poncirus trifoliata) is a superiorrootstock for satsumas and tangerines and isstrongly recommended. It induces good cold hardi-ness in the scion variety and results in favorableyields and high fruit quality. About the only otherrootstocks that are of value are sour orange,Cleopatra mandarin, and certain of the citranges(cross of sweet orange and trifoliate orange). Avoidthe Rusk citrange. This stock has a weak root sys-tem, and the tree is more susceptible to cold injury.The Carrizo citrange does not impart enough coldhardiness to the scion and is not recommended.

Flying Dragon is a dwarf selection of trifoliateorange that has been evaluated as a rootstock inCalifornia, Louisiana, and Florida since the late1970s. When sweet oranges or other types of citrusare budded onto this rootstock, the trees producedare about 1⁄5 to 1⁄3 normal size. Trees can be plant-ed every 6 to 8 feet in rows, with rows 7 to 15 feet

* Know the scion and rootstock to avoid combinationsthat are not cold hardy enough for Alabama.

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apart. This rootstock has not been evaluated inAlabama. Researchers are concerned that tree sizeand yields may be too small for commercial use,but limited grower trials look promising. However,Flying Dragon is suggested to home producers whowould like to grow citrus trees that may never be-come taller than 6 to 7 feet. It would also add vari-ety to the landscape.

The Cleopatra mandarin is a good rootstock formandarins/tangerines. It is outstanding in centralFlorida but probably not as good as P. trifoliata inAlabama. Sour orange is not recommended as arootstock for kumquats because of incompatibilityproblems.

PollinationWith the exception of Clementine tangerine and

certain tangerine hybrids such as Orlando tangelo,citrus trees are self-fruitful and do not requirecross-pollination. Thus, self-fruitful types of citruscan be grown as single trees. Cross-pollination re-quires that two or more varieties bloom at the sametime. Some varieties will not cross-pollinate eachother. Satsuma and navel do not produce viablepollen and thus cannot be used for that purpose.

Establishment and Care of Young Citrus Plants

Site Selection and SpacingCitrus thrives in full sun. Even partial shade

tends to result in weak tree development.However, planting citrus under the canopy of a treesuch as pine that does not have dense canopy canprevent frost from forming on the citrus tree.

Avoid planting trees near septic tanks or drainfields. Tree roots may clog the drain, and soapsand other cleaning products used in the home mayprove toxic to the trees.

Citrus trees do best on well-drained sandy loamsoils but will grow on many soil types if goodwater drainage is provided. Citrus plants that devel-op into trees, such as satsumas, kumquats, and tan-gerines, can be planted as close as 10 to 15 feetapart, although a spacing of 15 feet in the row and20 feet between rows is ideal. Smaller citrus plantssuch as kumquats and lemons can be spaced asclose as 8 to 10 feet if desired. Satsumas and othercitrus propagated onto dwarf Flying Dragon root-stock can be planted 6 to 8 feet apart in rows 15 to18 feet apart.

Locate citrus plants in a protected area if possi-ble, such as near a house or some other structure,preferably on the south side. This location provides

some protection from severe freezes. Usually, thewind associated with cold weather comes from thenorth to northwest. Avoid areas where trees wouldbe watered frequently by automatic lawn sprinklers.

Tree Selection and Planting ProcedureOne very valuable characteristic of most citrus

is that plants will begin fruiting the year followingplanting, especially those purchased in containers.Plants will also fruit quite effectively when left incontainers and used as patio plants. Most citrustrees for home plantings are purchased in contain-ers or as balled and burlapped plants. Healthy 1-year-old budded trees should be 3⁄8 to 5⁄8 inch incaliper, and 2-year-old trees usually measure 5⁄8 to1 inch in caliper (caliper is trunk diameter mea-sured 1 inch above bud union). These trees are theideal size for home planting. Plants of the smalleracid-type fruits are usually purchased in smallersizes. Plant citrus anytime during the year, althoughlate winter or early spring (past the danger of freez-ing temperatures) is the ideal time. A planting siteof 4 to 5 feet in diameter should be cleared of allweeds and grasses and the soil thoroughly spaded.

Dig a hole large enough to accommodate theroot ball. Remove the plant from the container andplace it in the hole, keeping the top of the root balllevel with the soil surface. If the tree is pot-bound,make several vertical cuts around the ball to stimu-late new root development. Fill the hole about one-half full with soil, and then add water and trampfirmly to settle the soil and remove air pockets.Allow the water to settle, and finish filling the holewith soil; apply water again. Pack the soil firmlyaround the trunk, adding additional soil if needed.Do not apply any fertilizer in the planting hole asroot damage may result. Construct a water basinaround the tree 30 to 36 inches in diameter and 4inches high. Water twice weekly for the first 2weeks unless rainfall is adequate (1 to 2 inches perweek during growing season). Gradually reducethe number of waterings to once weekly duringperiods of little or no rainfall.

The first growing season is critical in the life ofa citrus plant. Perhaps the most essential item is thewater supply. During this first growing season,trees should be adequately watered every 7 to 10days unless rainfall is sufficient. Keep an area atleast 4 feet in diameter beneath the tree free ofweeds and lawn grass to minimize competition fornutrients and water. If dense lawn grass is allowedto reestablish close to the tree trunk, the small treewill grow rather slowly because of intense competi-tion. Keeping this area free of weeds and grasses

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will also help reduce bark injury from mowers. Safeherbicides are available for effective weed control.

At the time of planting, cut the branches backto 6- to 12-inch stubs (this pruning is sometimes al-ready completed when plants are purchased). Thispractice helps balance the top with the functionalroot system, stimulates vigorous regrowth, andshould generally be used where plants are bare-root or ball and burlaped. Plants purchased in con-tainers usually require less pruning unless they aresomewhat pot-bound and require root pruning tocorrect the direction of growth. Very little pruningshould be required during the first growing seasonexcept to remove any sprouts below the scaffoldlimbs (primary structural branches originating fromtree trunk).

Ideally, scaffold branches should not be al-lowed to develop lower than 18 to 20 inches fromthe soil. The natural branching habit of citrus re-sults in structurally sound trees without any specialform of training or annual pruning; thus, the typeof tree training as normally practiced with peachesand apples is unnecessary.

FertilizationNewly planted trees should not be fertilized

until growth begins in the spring. If possible, use acomplete fertilizer such as an 8-8-8 that containsmicronutrients. A suggested fertilizer schedule forthe first 3 years is given in Table 2. Fertilizer appli-cations should not be made between August 1 andFebruary 15 during the first 2 years to avoid induc-ing untimely growth flushes during the winter.

During the first year, spread fertilizer in a 30-inch circle, and avoid placing any against the trunk.In subsequent years, the fertilized area should begradually increased. A good rule of thumb to fol-low is to fertilize an area twice the diameter of thetree canopy.

Ordinary lawn and shrub fertilizer can be usedfor citrus trees. However, this type of fertilizer mayonly contain the primary plant food elements nitro-gen, phosphorus, and potassium. For best perfor-mance from citrus plants, a fertilizer that containsthe secondary food and micronutrients—magne-sium, manganese, and copper—is very beneficial.The latter two elements, plus zinc and boron asneeded, may also be supplied through nutritionalsprays.

Cold ProtectionYoung citrus trees, even of the most cold hardy

type, cannot withstand freezing temperatures aswell as more mature, bearing trees can. Before thefirst freeze each fall, trees up to 4 years of ageshould be banked with clean soil to a height ofabout 15 inches. Soil banks should be removedafter the last chance of a freeze in early spring.Only the portion of the tree under the bank will beprotected. Wrapping material having good insulat-ing properties, such as spun fiberglass or foam rub-ber, also make effective protectors and can be usedin lieu of soil banks. Commercial trunk wraps arealso available. On average, soil banks provide atleast 10°F to 15°F protection, while the trunk wrapsavailable afford 6°F to 10°F protection. These mate-rials should be a minimum of 6 inches thick andmust make good contact with the soil.

Under Alabama conditions and when smallnumbers of trees are involved, polypropylene cov-ers provide the best protection for upper portionsof trees. The use of microsprinklers positioned toprotect lower and upper portions of tree trunksand scaffold branches is one of the better alterna-tives for freeze protection in commercial plantings.Although protecting the trunks and lower portionsof scaffold branches is essential for tree survivalduring a freeze, no crop will be produced follow-ing a winter in which all leaves are frozen anddrop. Therefore, protecting the leaves from freezedamage should be a major objective where possi-ble (especially for home gardeners). Leaves will bekilled if in contact with a plastic cover (and certainother types) during a freeze. For protection of anindividual tree on extremely cold nights, placingone to three electric light bulbs beneath the coverprovides a fair amount of protection. During a verysevere freeze, using a small electric or propaneheater beneath the cover provides substantial pro-tection. However, care should be exercised to avoidplacing the heat source too close to the plant or thecover.

Table 2. Suggested Fertilizer Schedule for Young CitrusTreesa

(pounds of 8-8-8 fertilizer per tree)

Growing March April June JulySeason 1 15–30 1–15 15–30

First 1⁄3b 1⁄2 2⁄3 1Second 1 1 11⁄4 11⁄2Third 11⁄2 2 2 2aThis schedule is designed for citrus plants that develop intomedium to large trees. Only half of these amounts or less willbe needed for smaller, shrubby citrus plants such as kumquats,limequats, calamondins, etc.bMake this application after growth begins in the spring, usual-ly 4 to 6 weeks after planting.

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Cold Hardiness and Factors Affecting Freeze Damage

Among the citrus types that are most easilykilled by freezing temperatures are citrons, lemons,and limes. Temperatures from the mid to high 20swill readily kill or severely damage these plants.Sweet oranges and grapefruit are somewhat morecold hardy and usually require temperatures in thelow to mid-20s before incurring major damage tolarge branches. Tangerines and mandarins are quitecold hardy, usually withstanding temperatures aslow as the low 20s before significant wood damageoccurs. But among the edible types of sweet citrus,the satsuma (also called satsuma mandarin and sat-suma orange), has the greatest degree of cold har-diness. Properly hardened bearing trees will with-stand temperatures as low as 18°F to 20°F withoutappreciable wood damage. Temperatures at groundlevel can be several degrees colder than tempera-tures around the canopy of the tree, especially ifthere is no wind.

Keep in mind that the temperature ranges givenabove refer only to leaf or wood damage. Citrusfruits easily freeze at 26°F to 28°F when these tem-peratures last for several hours. Further, a longerduration of freezing temperatures is required tofreeze fruits of grapefruit as compared with sweetoranges. And tangerines and satsuma fruits are themost easily frozen of the common citrus.

The particular temperature at which tissue of agiven plant will freeze and the degree of the dam-age sustained are functions of a number of factorsin addition to the species and variety involved.Some of the more important are the following:

• The freezing temperature reached• The duration of the minimal temperature• How well the plant became hardened or con-

ditioned before freezing temperatures occurred(The freezing point of tissue of a hardened citrusplant may be 5 to 6 degrees lower than an unhard-ened plant.)

• Whether the plant is wet or dry (The killingtemperature is 2°F to 4°F lower for a dry citrusplant.)

• Age of plant (A young plant cannot withstandas much cold as a more mature tree.)

Healthy trees are more hardy than diseasedtrees. Another complicating factor contributing toobservations by some that citrus plants seem tofreeze at higher temperatures in some years thanothers is the difference between air (ambient) tem-peratures and leaf (tissue) temperature. On a windynight with clear or cloudy skies, leaf temperaturewill be approximately the same as air temperature.

However, on a cold, clear night with little or nowind movement, leaf temperature can easily dropseveral degrees (3°F to 4°F) below air temperaturebecause of radiation heat loss. Thus, under the lat-ter circumstances, while the minimum air tempera-ture on a given night may have only been 25°F,actual leaf temperature of the plants may havereached 21°F to 22°F. The critical temperature isthat of the leaf or fruit and not the air temperatureitself. Trees with a good fruit crop are less hardythan those with no fruit.

Care of the Bearing TreeThe first 3 years should be devoted to develop-

ing a vigorous tree with strong scaffolds. Some fruitmay be borne the second and third growing sea-sons, although the quality may not be too high.Trees should begin to make significant crops in thefourth growing season.

Continue using the same 8-8-8 fertilizer (orequivalent) for bearing trees. Two applications peryear, March and June to July, are usually adequate.Fall applications (October to November) as prac-ticed in Florida are generally not needed. Applyfertilizer from near the trunk to well beyond theleaf drip of the tree (on large trees this usually in-volves fertilizing about 4 to 6 feet beyond the leafdrip). A reasonable rate in each application tomaintain healthy foliage and good fruiting is about3⁄4 pound of the 8-8-8 fertilizer per year of age ofthe tree (these rates are for sandy soils; clay soilsand others with greater inherent fertility would re-quire less fertilizer). After a number of years, a fer-tilizer containing nitrogen and potassium or just ni-trogen alone may prove adequate. A maximum of11⁄2 to 2 pounds actual nitrogen per tree per yearshould be adequate. If plants are remaining toovigorous in the fall and winter period, the fertilizerrate should be reduced.

As trees become older, problems may be en-countered with micronutrient deficiencies. An an-nual nutritional spray applied in the spring usuallycorrects the deficiencies. There are usuallyprepackaged nutritional spray mixes that can bepurchased from garden supply dealers. Thesemixes should contain manganese, zinc, and copper.Deficiencies of boron may be corrected with foliarsprays or soil applications. When iron deficiencysymptoms develop, chelated forms of this elementshould be applied to the soil.

The pH (acidity or alkalinity) of the soil inwhich trees are growing should be maintained be-tween 6.0 and 7.0. Apply dolomite, agriculturallimestone, or basic slag as needed to prevent thepH from dropping below 6.0. Your county

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Extension agent or garden supply dealer can assistin determining if a pH adjustment is needed.

Weed control around large bearing trees be-comes somewhat less essential. However, it is gen-erally beneficial to remove all weeds and lawngrass from beneath the canopy of the tree mechani-cally or by using safe herbicides. This approachalso provides a more attractive landscape design.Of particular importance is the removal of weedsand grass from the area immediately around thetree trunk. This growth tends to create ideal condi-tions for fungal organisms such as those causingroot rot at the base of the tree. Mulches are notnecessary for best tree performance but may beused to reduce weed problems. Mulching materialshould not be placed within 12 inches of the trunk.

Watering of bearing citrus plants will not benecessary in some years. But adequate watershould be provided as needed, particularly duringflowering and fruit setting in early spring and thedry periods of mid to late summer. A slow applica-tion of water over a several-hour period is prefer-able to a rapid lawn-type irrigation.

Pruning citrus trees on an annual basis is notnecessary. Actually, the only pruning usually re-quired is for the removal of water sprouts (suckers)and dead, damaged, or diseased limbs. Leave shortstubs when removing branches. This helps prevententry of disease organisms into the trunk.Historically, there has been a recommendation toseal all cuts larger than 1 to 2 inches with a safepruning paint, usually one with an asphalt basebeing preferred. However, studies over the past 20years indicate that healing occurs just as readily orbetter when no pruning paint is used. Until thismatter is resolved, growers may prefer to chooseeither option. Spring and summer are ideal timesfor pruning.

When citrus plants become too tall (above 12to 13 feet), overall management, including freezeprotection, becomes more difficult. It is suggestedthat selective pruning (thinning out type cuts ratherthan heading-back) be used in upper areas of trees.The ideal time for this pruning is in early to mid-spring after the potential for freezes has passed.Pruning in fall and winter could make plants moresusceptible to freeze damage.

Citrus plants in Alabama are always subject toinjury from cold weather. If trees are only slightlydamaged, prune them as soon as new growth indi-cates the extent of injury. However, regardless ofthe amount of injury sustained, no pruning shouldbe done until the danger of further freezes haspassed. If trees incur major freeze damage, allowthe first flush of growth to mature before pruning.

Such a tree will be less cold hardy than usual thefollowing winter.

Alternate bearing (fruiting every other year) canbecome a problem for some types of citrus. Treesthat alternately bear normally crop lightly (10 to 25percent of normal crop) following years whencrops are heavy.

As a group, mandarins have the worst tendencytoward alternate bearing. Satsumas, as well as tan-gerines, exhibit varying tendencies to alternate bearfollowing years of excessive cropping or otherforms of stress. Leaving fruits on trees for longperiods following peak harvest time can result inalternate bearing. Removing some excess fruit inheavy bearing years, properly harvesting fruit ontime, maintaining adequate soil moisture and nutri-tion, and reducing other stresses will help reducethe tendency toward alternate bearing.

Other Cultural Problems

Fruit SheddingHomeowners frequently become concerned

about the excessive shed of young blossoms andfruits in early spring. This natural shedding, or ab-scission, of blossoms and fruits is characteristic ofall citrus. Another natural fruit shedding occurs inMay and June when fruits are marble size. Keep inmind that only 1 or 2 percent (sometimes less than1 percent) of the blossoms are needed for goodcrops. Natural abscission of flowers and fruits aidsin preventing citrus from overproducing. However,navel oranges may drop throughout the growth pe-riod because of disease organisms in the navel ofthe fruit.

Leaf DropOccasionally, homeowners become alarmed

when healthy trees lose large numbers of theirleaves. In many cases, this is a natural drop (it maybe most noticeable in early spring). Citrus leaveslive for 18 to 24 months and then begin shedding,with some leaf dropping occurring throughout theyear. However, the homeowner should always bealert to other possible causes of leaf shedding, in-cluding mite damage, excessive or insufficient soilmoisture, cold damage, or root diseases.

Fruit SplittingIn late summer (August to September) fruit

splitting may be a problem with certain orangesand tangerines. This is a physiological problem notadequately understood. It usually occurs when aperiod of fruit growth cessation (growth stops be-

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10 Alabama Cooperative Extension System

cause of drought) is followed by a rapid increase insize as the result of a heavy rain. Other than allevi-ating moisture stress, little can be done about theproblem. This problem is most common on varietiesthat produce seedless or nearly seedless fruit.

Insect and Disease ControlCitrus fruits can be grown successfully in the

home grounds with little or no control of insectsand diseases. Fruits produced without pesticidesprays may be very poor in external quality as a re-sult of damage by several mites, insects, and fungaldiseases. Although these unattractive fruits mayhave little eye appeal, this external damage usuallyhas no detrimental effect on internal fruit quality.And the appearance of the tree may suffer, but sel-dom will trees be critically damaged by most citruspests. Natural biological control will assist in main-taining pests at low population levels.

For those who prefer to spray, three coversprays during each season should be sufficient. Apostbloom spray for scales, mites, and fungal dis-eases, a summer oil spray for scales and mites, anda fall mite spray usually are satisfactory. Commercialproducers usually need to apply at least a post-bloom spray to maintain fruit appearance adequatefor the wholesale/retail market.

During the past 5 years, Alabama producershave had to apply insecticides to control the newlyintroduced citrus leaf minor, which causes major fo-liar damage. It is often very useful to apply a post-bloom copper spray to control the fungal diseasesscab and melanose. Controlling mites is also neces-sary at times, particularly in the fall.

Formulating a spray program can be somewhatdifficult because of the many factors involved.Government regulations are constantly changing re-garding the use of agricultural chemicals. Manyhousehold insect sprays should not be used on cit-rus trees because they contain petroleum carriersthat injure the leaves or fruit. Consult your countyExtension agent for information on developing aspray program for home citrus trees.

AcknowledgmentThe authors are grateful to Larry Jackson,

University of Florida, and to Jack Hearn and otherUSDA scientists in Orlando for suggestions and as-sistance in preparing this publication.

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Citrus for Southern and Coastal Alabama 11

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Arlie Powell, Extension Horticulturist, Professor, and Dave Williams,Extension Horticulturist, Associate Professor, both in Horticulture at AuburnUniversity

For more information, call your county Extension office. Look in your tele-phone directory under your county’s name to find the number.

Issued in furtherance of Cooperative Extension work in agriculture and home economics, Acts of May 8 and June30, 1914, and other related acts, in cooperation with the U.S. Department of Agriculture. The AlabamaCooperative Extension System (Alabama A&M University and Auburn University) offers educational programs,materials, and equal opportunity employment to all people without regard to race, color, national origin, religion,sex, age, veteran status, or disability. UPS, 7M26, Revised Sept 1998, ANR-603ANR-603

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