Author, Chuck Ingels, Farm Advisor, Sacramento County
Edited by Judy McClure, Master Gardener Program Coordinator
Publication Number 31-S68 (Published October 2000)
Fruit trees will normally begin to bear fruit between two and five years after planting, depending mainly on the species and method of training and pruning. Most stone fruits beginto bear in year two or three, although cherries may not begin bearing foruptofive years after planting. Apples often begin to bear in abouttwotofouryearsbutpears cantakeonetotwoyearslonger. In addition, fruiting in many species requires pollination, as well as adequate irrigation, drainage, and fertilization.
Observe Flowering and Fruiting Characteristics
It is important to note whether your trees did not bloom at all; bloomed but did not set fruit; or bloomed and set, but most or all the fruit fell off at some point beforeharvest.Ifyourtreeshave neverbloomedandtheyareolder than the bearing ages listed above, you may be pruning too severely.Most fruit trees require thedevelopmentofspursorshort shoots on which flowers form, although peaches and nectarines bloom on longer shoots.It is important,therefore, not tocut off all the one-year-old spurs and shoots.It is also important to provide adequate light tothese fruiting shoots by thinning out crowded growthand/oropeningthe center, especially by summer pruning (see Training and Pruning Fruit Trees).Lack of sunlight can also prevent flowering and fruit set; trees should have at least six hoursofdirectsunperday.Ifyou are pruning appropriately andyour tree is healthy, but still no flowers form after several years, consider grafting to a different variety or replacing the tree.
Trees that consistently flower but setlittleornofruitprobablylacka pollinizer variety (see Pollination section below).However, the problem could be cold and/or wet weather during bloom, which reduces the activity of pollinator insects, preventing the transferof pollen.Such weather conditions alsopreventpollentubegrowthin the female parts of the flower.
Inclement weather is often more of a factor on early flowering species such as almond and plum.Lack of nitrogen can also lead to poor fruit set.If nitrogen deficiencyissuspected,fertilizein the summer to increase the nitrogen storage in the tree over the winter; this stored nitrogen is utilizedforflowering afruit set the following spring.
Ifyourtreesbloomedandsetfruit normally, but thefruit dropped off prematurely, any of several factors could have contributed. Sometimes fruit appears toset butdropsinApril;thiscouldstill be a lack of pollination.
Any factors that cause poor tree health can affect fruit set and retention.Forexample,excessor insufficient water during the summer can cause fruit to drop, but you would also see drooping or yellowing leaves.Other contributing stresses include root constrictions caused by hardpan or compacted soil, sunburn or borer insects on the trunk or branches, and pests such as soil nematodes, root rot, bacterial canker, brown rot of twigs, powdery mildew, and spider mites.
Encouraging Precocity
Trees with vigorous, upright growth, such as cherry and pear, tend to begin bearing later than those with spreading habit, such as peach and apricot.However, thesetreescanbeencouragedto bear earlier by bending upright branches outward during the growing season, before they become too stiff to bend.
Branchescanbeheldin place bytying them to a stake, a string attached to the ground, or a trellis (espalier). Also,avoidexcessive heading cuts, especially during the dormant season, since heading encourages vigorous growth and reduces flower development.Bending unheaded, upright branches outward is a proven method for developing spurs and flowers quickly.
Climate and Weather
Mostfruittreesneedasubstantial amount of cold winter weather to end their dormancy and to promote spring growth. Aftermild winters, spring growth and flowering are delayed and irregular, the flowering period is extended,andfruitsetisreduced. The extended bloom increases the chance that inclementweather will cause blossom diseases, such as brown rot orfire blight.
The chilling requirement is the number of hours below 45°Ffrom November1throughFebruary15. Fruit tree species and varieties differ greatly in the number of hours required to fully break dormancy.The label on a purchased fruit tree will oftenstate the chilling requirement.
The Sacramento area usually receives adequate chilling, averaging about 900 to 1,000 hours.When possible, select varieties with a chilling requirement below about 700 to 800hours,sincetherearesome years in which we receive less than 800 hours.Varieties requiring 1,000 hours or more may set poorly in some years.
Low-chill varieties are availableformostfruittreespecies,andthe chilling requirement is usually stated on the label.
Sometimesfrostduringorshortly after blossoming can cause young fruitlets to abort, even though no frost damage is seen. When a heavy frost is expected, covering the trees with plastic or bed sheets will sometimes prevent injury to the expanding buds or blossoms, providing temperatures do not fall too low and the cold weather is of short duration.
Pollination
Most fruit treesneed to be pollinated.Without sufficientpollination, they may blossom abundantly but will not bear fruit.A pollinizer is atree or branch of a differentvariety with a similar bloom period.Pollinators (usually bees) carry pollen from the flowerofone variety to the flower of another variety.
Most species of fruit trees have ‘perfect’flowers:boththeanthers, which contain pollen, and the pistil, which develops into fruit, are located in the same blossom. Trees that bear fruit through self- pollination, or set fruit without pollination, are called “self- fruitful.” However, there aremany fruit species with perfect flowers that cannot produce fruit from their own pollen.These require pollen from another variety and are called “self-unfruitful.”
Somespeciesdonotfitintoeither category.Pistachio and kiwifruit have male trees that produce pollen and female trees that produce fruit.To grow them successfully, it is necessary to plant at least one tree of each gender near each other.
Self-Fruitful Types
Almostallcitrusspeciesare“self- fruitful.” Other self-fruitful species include quince, sour cherry, most apricots, fig (except the Smyrna type), peach (except ‘J.H. Hale’ andsomeothers),andEuropean- type plums and prunes.Some European pears are also self- fruitful.‘Bartlett’ pear is parthenocarpic,whichmeansthat no pollination is required to set fruit (only in California).Some cherriesareself-fruitful,suchas ‘Lapins,’‘Stella,’and‘Sunburst.’ Many apple varieties are self fruitful, including ‘Braeburn,’ ‘Empire,’ ‘Fuji,’ ‘Gala,’ ‘Granny Smith,’ and ‘Pippin.’
Self-Unfruitful Types
“Self-unfruitful”speciesinclude manyapple,Asianpear,sweet cherry, and Japanese plum varieties.The label usually indicates varieties that will pollinate your tree.
Topollinateadequately, plant two or more varieties no further than 35 to 50 ft. apart- the closer, the better. Alternatively, you can graft a pollinizer variety onto the tree (see “Bud Grafting,” EH Note #85).Theuse of bees can improve pollination.In the interim before a pollinizer variety is grafted or planted nearby, you can place flowering branches of a pollinizer variety in a jar filled with water, and set the jarandflowersinthetreecanopy. Bees will visit these flowers and will pollinate the tree’s flowers.
Somecherrieshavefairlyspecific pollinizer requirements.‘Bing,’ ‘Lambert,’and ‘Royal Ann’ cherry trees do not pollinate one another.Plant a pollinating variety such as ‘Black Tartarian’ or ‘Van,’ or a sour cherrysuch as ‘Montmorency’ nearby.
Foradditionalinformationon pollinationandvarieties,see these Web sites:
- FruitandNutResearch& Information Center
- DaveWilson Nursery
Biennial Bearing
Occasionally, certain fruit treessuchasapplesbear heavily one year and sparselythe next.This is called “biennial bearing.” Thespring-floweringbudsofmost deciduousfruittreeshaveactually been formed during the previous summer.Therefore,anespecially heavy crop one year may prevent adequate flower budformation for the following year because the carbohydrates produced through photosynthesis are used preferentially for fruit production during the “on” year.
Biennialbearingofapplesis difficult to alter or correct. However, you can induce a return to normal annual fruit productionby heavily thinning during the year in which the trees are producing their large yield (see “Fruit Thinning to Increase Fruit Size and Maintain Healthy Trees," EH Note #84).About 30 to 40 healthy leaves are needed to produceeach fruit.
Adapted from Environmental Horticulture Note #68, University of California Cooperative Extension, Sacramento County