Site Selection
Long summer days, cool nights, and a mostly dry season are ideal conditions for growing fruit trees. Fruit trees require freezing or close to freezing temperatures during the winter, but generally need at least 150 days between the last spring frost and the first fall frost so blossoms are not damaged in spring and so fruit will mature in the fall.
Do not plant in low spots or areas that flood frequently. If you are planting on a site where the soil is shallow because of a hardpan, break through the hardpan when preparing for planting. Do not plant trees too close together, as this may cause poor growth.
Most fruit trees do best in areas with full sun, good air movement, and well-drained soils at least 4 feet deep. Plant in unshaded areas as much as possible to prevent diseases. The best soils are fertile, slightly acidic sandy loam soils free of alkali or salinity. Avoid sandy, high clay, or shallow soils, although pears can tolerate clay or wet soils better than other fruit trees can.
Chilling hours are defined as the number of hours the temperature is below 45° F. It is important to make sure your area has adequate chilling hours because inadequate chilling will result in delayed foliation and uneven fruit development.
For plums and prunes, there are low-chill varieties including the interspecific hybrids (crosses between apricots and plums) that will tolerate warmer conditions. Japanese plums require from 500 to 900 chilling hours and European plums require 700 to 1,000 chilling hours to satisfy the chilling requirement.
Planting
The ideal planting time for fruit or nut trees is during the dormancy period in the bare-root stage during winter or early spring. Plant as soon as possible after receiving them from the nursery, and do not let them dry out. The roots are very sensitive and must be kept wet and protected from harsh temperatures. Pack roots in peat moss or similar material and keep plants in cool, shady locations until ready to plant.
Avoid planting in a hole or a low-lying area to prevent diseases such as root rot. Plant in raised beds, or on a ridge or mound of soil several inches high and several feet across in areas where drainage is poor or soil is highly amended. Plants will settle as organic matter in the soil decomposes. The hole should be about 1.5 to 2 feet wide and about 1.5 feet deep. Do not dig the planting hole any deeper than the roots of the tree as purchased.
When you are ready to plant, remove the packing from the root system and examine the roots. Cleanly remove broken or decayed roots prior to planting. Soak the roots in cool water for about 6 to 12 hours and then place the tree in the hole, being careful to spread out the roots. When planting, make sure all the roots are in their natural position. Avoid curling them around the planting area. Refill the hole with the original soil from the site and avoid adding organic amendments and fertilizers. While refilling the hole, settle the soil around the roots to avoid air pockets. Leave the graft union 2 inches above the soil line. Water in after planting. Fertilizer is not usually necessary the first year.
Watering
Fruit and nut trees require consistent, uniform soil moisture. Water is very important for young trees, especially during the first year when the root system is developing. Stress during early growth or during fruit production will reduce yields and fruit quality and may make trees more susceptible to boring insects or diseases. Moisture should be replaced well before the trees begin to show stress. Young trees may need up to 3 to 5 gallons of water per week. Avoid frequent light watering with sprinklers as this creates a shallow root system. A garden hose, soaker hose, or drip system can provide good deep watering. Sandy soils may have to be watered every 3 to 5 days; heavier soils may need only to be watered every 1.5 to 2 weeks. During hot weather, young trees may need to be watered more often. Avoid prolonged saturation. If weather is windy, be sure to stake young trees, otherwise they will lean in wet soils.
Do not water established trees near the trunk and lower branches, as this promotes root and crown disease. Water plants when needed around the drip line and beyond. Avoid overhead sprinklers when possible. Try to water deeply and infrequently (every 2 to 3 weeks) by irrigating for 12 to 24 hours to wet to a 3- to 6-foot depth. If using a drip system, water more on a continual basis. Reduce water in late summer and fall.
Pruning
Most of the fruit on plums is borne on short spurs located on wood that is 2 to 3 years old. Some older spurs may be thinned out to reduce fruit set. New whip shoots should be pruned back by one-half to stimulate side branching, which is where the new fruit spurs will develop. Thin out the center of the tree to improve light penetration there.
Thinning
Japanese plums tend to set more fruit than the tree can carry, which results in small, poor-quality fruit. Hand thinning will help to increase size of the fruit and improve the quality. Thinning can be done any time between bloom until just before harvest, but fruit size at harvest is generally directly related to the time of thinning. The earlier you thin, the larger the fruit you will have. Ideally, thin as soon as you can see the developing fruit on the tree. Space fruit about 4 to 6 inches apart on the branch and break up the fruit clusters. Focus on damaged fruit first. Then remove fruit at the ends of branches that may be weakened by heavy fruit. European plums do not require extensive thinning unless fruit set is very heavy.
Training
Young trees are pruned to develop a tree structure which supports the limbs that ultimately support the heavy fruit load during the season. The goal of training is to develop a sturdy tree and a canopy that is capable of producing large crops and fills its allotted space. Training occurs during the first 2 to 3 years after planting and should be completed before fruit is allowed to set.
Figs and Japanese plums can be trained to the open center vase or to a delayed open center. A delayed open center system is similar to the open center but has wider spacing between scaffold branches. Because figs are prone to winter injury in colder climates, it is best to grow figs as a bush, where they can push enough new growth to produce a crop after cold injury. They should be pruned in late winter to keep in bush form by cutting back to about 8 feet.
European plums and prunes are trained to a modified leader system where a central leader is allowed to grow to a height of 5 or 6 feet and is then headed to an outward growing limb. As the tree grows, limbs that develop from buds on the ends of very short shoots or from "necked buds" tend to be weak and break out easily. Remove necked buds to favor the development of widely attached branch angles.
Remember that exposed limbs on young trees easily sunburn. Protect exposed limbs with a 50:50 mix of white interior latex paint and water or whitewash.
First-Year Pruning
During the first year after planting, fruit and nut trees have different pruning requirements. To ensure a low-profile tree, cut back plum and prune trees to 18 to 20 inches after planting.
Fertilizing
Maintaining a good fertilization program can keep your plants vigorous and help prevent infections of bacterial blast or canker, oak root fungus, and powdery mildew.
As a general rule, nitrogen should be applied annually, usually during the growing season. To improve fruit quality and color, nitrogen levels should be low but not deficient as the harvest nears. Nitrogen fertilizer can be applied in the spring or split between spring and just after harvest. Excessive nitrogen can cause softer fruit, poor fruit color, and reduced storage and shelf life; it can also increase problems with numerous pests. Typically, mature trees should receive about 3 to 5 pounds of ammonium sulfate per year or 2 pounds of urea per year depending upon soil fertility and local growing conditions. Apply about a foot away from the trunk, continuing to the drip line, and water thoroughly after application.
Zinc is also commonly deficient. Affected trees have small new leaves. This deficiency is best corrected by spray applications. Spray with a "chelated zinc" during the growing season. Repeat if new growth still shows deficiency symptoms.
Harvesting and Storing
The best way to tell if plums are ready to harvest is by the fruit's firmness and taste. Plums should be just beginning to become soft and should taste sweet and juicy.
Japanese plums are harvested firm ripe. The early maturing varieties will need to be harvested several times over a period of weeks, because not all the fruit will be ready at the same time. The later varieties usually can be harvested at one time. To get the fruit to ripen indoors, keep them between 60° and 80° F. Higher or lower temperatures may cause internal browning, mealiness, or off flavors. For longer term storage, temperatures between 31° to 32° F will provide the optimum storage conditions for about 2 weeks. This narrow temperature range is difficult to maintain accurately in home refrigerators.
European plums are harvested just as they begin to soften and the background color on the skin of the fruit becomes yellow.
Prunes are allowed to ripen fully on the tree. Wait until a few fruits naturally fall, then harvest completely and allow them to dry naturally.
Sanitation
Sanitation is a necessary management tool in all home orchards because of the long life of trees. Perennial weeds, nematodes, and certain disease pathogens are difficult to control after trees become established. Prevent the introduction or spread of infestations by removing infected limbs and fruit. Disinfect cutting tools periodically during pruning and whenever they come into direct contact with diseased tissue. Clean equipment used in other areas to avoid introducing pathogens, nematodes, or weeds.
Sanitation Tips
- Remove diseased wood as soon as it becomes evident. Dispose of the prunings immediately to prevent them from becoming a source of new infections.
- Remove stumps, brush piles, and debris. Brush, thinnings, and other debris can harbor diseases as well as vertebrates and insects. Removing stumps may prevent population buildups of wood-boring insect pests.
- Remove diseased shoots, leaves, and fruit on trees and on the ground.
- Remove roosting, nesting, or resting areas that may attract large numbers of crop-destroying birds.
- Keep the tree crown area free of weeds to reduce crown rot infections.
- Spot-treat perennial weeds to prevent their spread.
