Managing Fruit Trees In The Home LandscapeTable 1 presents a summary of management requirements for the fruits and nuts most commonly grown in Texas. These requirements are discussed in detail in the following pages.
One of the most common questions among home gardeners is how various fruit and nut crops are propagated. Table 2 summarizes the most popular methods of propagation for Texas crops.
Under natural conditions, plant nutrition is usually not a problem because slow growth and low production are acceptable. But the homeowner usually wants many large fruits as soon as possible, so a judicious fertility program is necessary.
When buying a fertilizer, it is important to know what the numbers mean. A fertilizer label usually has three numbers, such as 10-10-10. These numbers represent the percentages of nitrogen, phosphorus and potassium, respectively, in the mix. In other words, a 50-pound bag of 10-10-10 has 5 pounds each of N, P2O5 and K2O. But that accounts for only 15 pounds out of a 50-pound bag. The rest is either other salts or inert fillers, such as sand, perlite or other materials.
Nitrogen. Nitrogen is necessary for all vegetative growth-roots, leaves, stems, flowers and fruit. Nitrogen deficiency causes the plant's lower leaves to turn yellow, while excessive amounts delay maturity, causing increased vegetative growth and decreasing cold-hardiness. Nitrogen is needed in all parts of Texas to maintain healthy plants.
Phosphorus. A long-standing fertility recommendation has been to apply a high-phosphorus fertilizer anytime a plant fails to bear. However, in most situations, phosphorus does not increase blooming in a fruiting plant. Phosphorus fertilization is needed most in sandy soils, since clays and loams ordinarily have adequate amounts for perennial plants.
Iron. Many areas have problems with iron deficiency even though adequate amounts are present in most Texas soils. The alkaline (pH over 7.0) soils tie up iron, making it unavailable to the plants. Iron deficiency is normally found in new growth and is characterized by yellow leaves with a "road map" appearance because almost all the veins remain green.
Zinc. Zinc deficiencies are a problem in pecans in most of the state. Zinc deficiencies are characterized by small leaves, rosetted (highly branched, short, bunchy) growth, twig and limb dieback and sometimes tree death. Leaf veins have a band of green on each side, giving the leaves a striped appearance.
Choosing A Fertilizer
Because Texas has such variability in its soil types, a single broad fertilizer recommendation is not applicable in all cases. The best means of determining your individual soil need is to have a soil test done by the Texas Agricultural Extension Service's Soil Testing Laboratory. Information on sampling techniques and prices is available from your county Extension office.
Where soil tests are unavailable and a general recommendation is needed, use the following guidelines. On sandy soils, use a complete fertilizer such as 15-5-10 for most fruit crops. Acceptable rates are 1 pound per inch of trunk diameter per year of age for trees up to 10 years old and 1 pound per 10 feet of row for blackberries and grapes.
On loams and on clay soils, the only element generally required is nitrogen, which can be furnished with 1 pound of 21-0-0 per year of age or inch of trunk diameter up to 10 for trees or 1 pound per 100 feet of row for vine crops.
Iron deficiencies are common on most of the alkaline soils in Central, South and West Texas. Generally foliar iron sprays do not work well to correct iron deficiencies in fruit crops. Soil-applied iron chelates (FeEDDHA) at label rates are the most effective. Iron sulfate (copperas) is seldom effective as a remedy for iron chlorosis of fruit trees or berries. Where iron deficiencies are a problem, do not use fertilizers containing phosphorus, as they usually make the problem worse.
Zinc deficiency on pecans is a problem in most of Texas; therefore, make at least three applications of a foliar zinc spray each year during April and May for maximum growth. Do not spray other plants with zinc at the rates used on pecans since leaf burn and defoliation may occur. Zinc nitrate is least likely to cause burn to other plants in the landscape. When zinc deficiency is a problem on other crops, it can usually be corrected by soil applications of zinc sulfate.
To maximize production and maintain plant health, it is important to irrigate plants through periods of stress. There are many ways of determining when and how much to irrigate. Begin watering when the soil begins to dry out after a rain. If your area experiences prolonged wet periods, wait about 2 weeks before starting.
It is important that you apply enough water to wet the soil to a depth of at least 12 inches with each irrigation. You can check the irrigation depth by pushing a metal rod into the soil at the wetted area. Keep pushing until resistance stops the rod's penetration: the length of the underground portion of the rod is the irrigation depth. When the soil is wetted to a depth of 12 to 18 inches at each watering, plants usually do not suffer from drought stress, even when waterings are missed.
In areas where the lawn is not watered, trees still require water. You can provide water in a number of ways, but trickle or drip irrigation is one of the best methods. Trickly irrigation kits for lawn and garden use are readily available. When using drip irrigation, place enough emitters around the plants to water 50 to 70 percent of the root system. During hotter months of the growing season, operate drip systems a minimum of 10 to 12 hours, 1 day per week, to maintain adequate soil moisture. They can be controlled by electric time clock, by switching tensiometer or by hand.
Training And Pruning
Training and pruning are essential parts of the management program for any fruit or nut crop. Training the plants helps to ensure that they will grow properly and bear successfully-and that they will be attractive additions to your landscape.
Tree Training Systems. The two most commonly used tree training systems are the open center and the central leader systems. Open center systems are generally used on peaches, plums, apricots and almonds. Apples, pears, pecans and persimmons are normally trained to a central leader. There are good and bad points to both systems, but neither system dictates that the trees be pruned a certain way. In fact, many trees are not pruned or trained at all. However, contrary to some popular beliefs, pruning is important for producing most fruit and nut crops. But don't get bogged down in specifics; instead, keep general principles in mind.
Both training systems start out in essentially the same way. Fruit trees are 30 to 36 inches tall or larger, or nut trees 4 to 7 feet tall, are cut back by one half at planting with all side shoots removed (Figure 4). This forces out strong vigorous shoots which can be easily trained to the desired system.
The open center or vase system of training simply involves maintaining a framework of branches around an open "vase" in the middle of the tree. This allows sunlight to penetrate into all parts of the tree, allowing for good production in all areas.
The key to open system training is to develop a strong open center framework in the first 2 or 3 years (Figure 5) and to subsequently maintain this shape (Figure 6). This later pruning involves the heading-back of shoot terminals to outward-growing branches, the removal of large, fast-growing branches that fill the open center and the removal of crowded branches and any diseased or broken limbs. This reduces the height and keeps the center of the tree open.
The central leader system consists of a central trunk around which scaffolds (primarily side branches) of the desired number and spacing can be arranged with wide-angle crotches. Three to eight scaffold branches are commonly developed from the central leader trunk.
A "modified" central leader tree is cut back each winter and a new central leader shoot is selected each spring. Pecans, apples and pears are generally pruned in this manner (Figure 7). The top center of modified central leader trees is often thinned out for better light penetration into the interior of the tree canopy. Uniformly space the scaffolds around the central leader.
Further information for pruning specific crops is available in these Texas Agricultural Extension Service publications:
- B-1591, "Home Fruit Production-Figs."
- B-1598, "Home Fruit Production-Pears."
- B-1607, "Home Fruit Production-Apples."
- B-1629, "Home Fruit Production-Citrus."
Grape Training. Grapes require severe pruning to develop high shoot vigor during training and to maintain production of quality berries on mature vines. Prune back leaving only two buds at planting, as shown in Figure 8.
First growing season: Allow growth to develop at random to establish a good root system.
First winter: Prune off all growth except one shoot with two good buds, as shown in Figure 9.
Second growing season: Choose the most vigorous shoot and train it up a stake. Tie the vine to the stake every 6 inches. Keep side shoots pinched off, but keep leaves on the trunk. When the shoot reaches just above the cordon wire, pinch out the tip to force lateral branching. Train laterals (arms or cordons) down the wires, tying regularly to keep the cordon straight and in place. See Figure 10.
Mature vines: Cane pruning and cordon pruning are two basic systems commonly used. With either system, winter-prune the vine, leaving a total of about eight buds of the previous summer's growth prior to the third year and 20 to 40 buds per vine on mature vines.
Cane pruning is best for varieties that produce few fruit on basal buds such as Thompson seedless and for small clustered varieties. With this system, all four arms are removed each winter. One-year shoots (renewal canes) are tied to the wires to replace the old arms. Cut off the tip of each renewal cane at a point where it is approximately 3/8 inch in diameter. See Figure 11.
Cordon pruning is most commonly used in Texas vineyards. This system consists of leaving about seven upright spurs (one to two buds per spur) on each cordon, as shown in Figure 12. All other growth is removed. Use a "clothesline-like" T-top trellis with a wire at each end to more efficiently catch and spread the upright can growth. For this method, a 2-foot wire T-top replaces the single top wire shown.
Muscadine grapes are usually cordon-trained, but because of greater vine vigor, muscadine vines can be allowed to support up to four cordons with spurs of three to five buds each, as shown in Figure 13.
Grape arbors are easiest to maintain using cordon training. Develop parallel, spur-pruned cordons about 2 feet apart across the top of the arbor. Black Spanish and Champanel are excellent arbor varieties. Muscadines also make good arbor grapes in East Texas.
Berry Training. The types of blackberries and raspberries range from erect, freestanding plants to trailing vines. The training system differ according to the type of growth.
Erect blackberries and raspberries produce low, sprawling growth the first year after planting, but in the second and subsequent years new growth is very erect. Clip the tips from new canes two to three times from May to September to force side-branching and to develop a full, compact hedgerow, as shown in Figure 14. Prune the hedgerow much as you would an ornamental hedge. A well-pruned hedgerow of erect berries does not need trellis support.
Fruiting canes die soon after the fruit have matured. An accumulation of dead canes poses a considerable nuisance when picking berries, so it is best to keep dead canes removed.
Winter pruning is not needed if the berries are properly pruned in the summer.
Trailing and semierect blackberries and raspberries should be trellised, as shown in Figure 15. A proper trellis allows the canes to be spread for good sunlight exposure.
Tip new canes two or three times each summer to encourage more branched growth. Leave new canes (primocanes) of trailing blackberries on the ground each winter to help protect them from freeze damage. Trellis the canes before they begin growth in mid-March. Remove and destroy fruiting canes (floricanes) after harvest in the summer as soon as they die.
"Mature" and "ripe" are not synonymous terms when applied to most fruits. Mature fruit have all of the internal components necessary to fully ripen even if they are picked before they are ready to eat. But a ripe fruit is at the point at which it is ready to eat. Many fruits, including peaches, reach maturity while still hard, several days before they ripen.
Harvesting fruit at proper maturity and storing it under proper conditions can be just as important as a good spray program. Immature fruit lacks characteristic flavor and texture, while over-ripe fruit is usually mealy with rapid tissue breakdown and does not hold up in storage.
Where ripening characteristics are concerned, fruits fall into three categories:
Besides fruit maturity, other important points to consider are proper handling and storage. The fruit's skin or peel provides a natural barrier to insects and diseases; therefore, gentle handling to prevent punctures and bruises is essential. Discard any diseased or bruised fruit or use it immediately. Proper storage is a real key to maintaining fruit quality. Fully ripe fruits store best at refrigerator temperatures.
- Those picked green-mature for storage, but whose flavor is not as good as that of fruits that reach full maturity on the tree (such as peaches, nectarines and plums).
- Those picked and ripened in storage, whose flavor is as good or better than tree-ripened (including avocados and bananas, which mature on the tree but do not reach peak flavor until picked and held for 4 to 5 days at room temperature).
- Those fruits that must ripen on the tree or vine (such as grapes, blackberries and citrus).
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