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Peach – Prunus persica

PEACH TREE TAXONOMY

The peach tree (Prunus persica L.) Batsch) belongs to the Prunoideae subfamily of the Rosaceae with other species collectively referred to as “stone fruits”. The subgenus Amygdalus contains the commercially important peach and the almond tree.

Cultivars
There are thousands of types of peach trees and cultivars worldwide. The peach tree is far more are cultivated in economic quantities than for many other tree fruits. Okie (1988) provides detailed descriptions for many of the cultivars used in the United States. Cultivars fall into one of three major groups:

Nectarines – while labeled and marketed differently from peaches, nectarines are simply fuzz-less peaches.
Freestone peaches – fresh market peaches
Clingstone peaches – used primarily for canning

The adherence of the flesh to the stone per se doesn’t affect canning quality, but firm flesh texture is linked to the clingstone trait, so clingstones are used for canning. Clingstones also retain shape better, and have brighter color and clearer juice than freestone when canned. White-fleshed cultivars are popular in the Orient, but yellow flesh cultivars are preferred in the USA. However, more interest in white-fleshed peaches and nectarines has arisen in the last 5-10 years.

ORIGIN AND HISTORY OF THE PEACH TREE (PRUNUS PERSICA), HISTORY OF CULTIVATION

Peaches were probably the first fruit crop domesticated in China about 4000 years ago. Cultivars grown today derive largely from ecotypes native to southern China, an area with climate similar to that of the southeastern USA, a major peach growing region. Peaches were moved to Persia (Iran) along silk trading routes. In fact, the epithet persica denotes Persia, which is where Europeans thought peaches originated. Greeks and especially Romans spread the peach throughout Europe and England starting in 300-400 BC. Peaches came to the new world with explorers of the 16th-17th centuries, with the Portuguese introducing it to South America and Spaniards to the northern Florida coast of North America. Native Americans and settlers distributed the peach across North America into southern Canada, and it is cultivated in 2/3 of the 48 contiguous states today.

WORLD AND UNITED STATES PEACH PRODUCTION

World (2004 FAO) – 15,561,206 MT or 34 billion pounds. [Note: world production data includes both peaches and nectarines] Peaches and nectarines are produced commercially in 71 countries worldwide on about 3.5 million acres.

Top 10 Countries
(% of world production)
1. China (44) 6. France (3)
2. Italy (13) 7. Turkey (3)
3. USA (10) 8. Iran (3)
4. Spain (8) 9. Chile (2)
5. Greece (7) 10. Argentina (2)

United States (USDA 2004) – 1,410,000 MT or 3.1 billion pounds. The total value of the industry is about $550 million. Peaches and nectarines are produced commercially in 29 states on about 114,000 acres.

Freestone peaches: 46% of total production; CA, SC, GA, NJ, and PA produce the most; value = $300 million, price averages 33 ¢/lb.
Clingstone Peaches: 35% of total production. All produced in California; value = $132 million, acreage = 31,000, price = 13 ¢/lb.
Nectarines: 19% of total production. Almost all produced in California; value = $114 million, acreage = 36,500, price = 19 ¢/lb.

For the most up to date statistical data on United States and World production numbers please refer to the following two websites:

World: The Food and Agriculture Organization of the United Nations Statistics Division (FAOSTAT). FAOSTAT

United States: The United States Department of Agriculture National Agricultural Statistics Service (USDA Ag Stats). USDA Ag Stats

BOTANICAL DESCRIPTION OF PEACH TREES

Plant
A vigorous growing, but small tree with a spreading canopy, usually 6-10 ft in cultivation. Trees are short-lived, generally living only 15-20 years, and even less on sites with a history of peach cultivation. Leaves are linear with acute tips, finely serrate margins, folded slightly along the midrib, sickle-shaped in profile, 2-6″ in length.

Flowers
Light pink to carmine, to purplish; 1-1.5″ in diameter. Ovary is perigynous, surrounded by a hypanthium.

Pollination
Self-pollinating, normally grown without pollinizers.

Fruit
A drupe. The bony endocarp (pit) surrounds a single, large, ovate seed. The flesh is the mesocarp, the skin the exocarp. Trees are very precocious, producing some fruit in the 2nd year after planting. Peaches require extensive thinning (80-95% of flowers) for proper size development. Usually, thinning is done by hand 30-45 days after full bloom, leaving about 1 fruit per 6 inches of 1-yr-old shoot length.

   

PEACH TREE GENERAL CULTURE

Soils and Climate
Soils – deep, well-drained soils, loamy to moderately sandy soils are best. Sites previously planted with peaches are avoided since they are prone to the “peach tree short life” syndrome (PTSL, also called peach tree decline), which greatly reduces orchard productivity. Several nematodes attack peach roots, resulting in poor growth and reduced longevity. Ring nematode (Criconemella xenoplax) has been implicated as the predisposing agent for PTSL, and they move fastest in sandy soils.

Climate – less cold hardy than many tree fruit species and earlier to bloom, frost is a problem in almost all growing areas of the world. Peaches are frequently cultivated in Mediterranean climates. On average, most cultivars have chilling requirements of 600-900 hrs. Peaches do not require cool nights to develop red skin color like apples; red color is more a function of cultivar and light exposure. Peaches ripen during the summer months in most climates, but develop good quality in regions with cool as well as warm summer temperatures.

Propagation
Peaches are T- or chip-budded generally onto seedling rootstocks.

Rootstocks

Peach Tree Short Life is a rootstock- and soil-related syndrome or complex, not a disorder attributable to a specific organism. It is common in the southeastern USA. PTSL is characterized by sudden death of trees above the soil line in spring, that were apparently healthy the previous fall. Profuse suckering usually occurs since roots are not killed. PTSL can be avoided by not replanting trees on old peach sites, or by using ‘Guardian’ rootstock, which is tolerant. Predisposing factors such as low soil pH, hardpans, low nutrient levels, ring nematode buildup, cultivation, fluctuating winter temperatures, fall pruning, and use of Nemaguard rootstock all accentuate PTSL.

Rootstock Characteristics
Bailey  Cold hardy rootstock with good overall performance; best in the northern states
Guardian Vigorous rootstock with resistance to peach tree short life syndrome; slightly more expensive. Used extensively in the eastern USA, and in areas where peaches were planted previously.
GF677 (Amandier) A peach-almond hybrid for adaptation to high pH soils; highly vigorous; not well adapted for eastern US
Halford Good overall rootstock for northern states
Lovell Moderately invigorating rootstock with fair resistance to peach tree short life
Nemaguard Invigorating rootstock with resistance to root knot nematode; susceptible to other nematodes and peach tree short life
Siberian C Cold hardy rootstock used only in the northern tier of states and Canada; short-lived and poor in the southern states

Planting Design, Training, Pruning

Planting Design – Free-standing peach orchards – rectangular spacings of 18 x 20 ft (110 trees/acre), or 12-15 x 18 ft (161-202 trees/acre), Trellised systems – 300-500 trees/acre. Pollinizers are not needed, but growers must plant several different cultivars to extend their marketing season, since peaches ripen quickly and cannot be stored for more than 1-2 weeks.

Free-standing peach trees are trained most commonly to open center with 3-5 scaffolds radiating from the trunk 18-36″ above the ground.

 

Peach trees can be trained to central leader.

 

Peach trees can also be trained perpendicular V.

In addition to the planting designs pictured here, a variety of trellised systems are also used in Europe.

PEACH HARVEST, POSTHARVEST HANDLING

Maturity
The best predictor of maturity is background color. Background color of fruit changes from green to straw-yellow during ripening, and fruit with a fair degree of yellow and enough firmness to ship are mature enough for harvest.

Harvest Method
Peaches are harvested by hand. Usually, trees are picked 3-4 times at 2-3 day intervals, taking only the firm mature fruit at each picking.

Postharvest Handling
Packing line operations are standard; fruit are first hydrocooled to reduce temperature, then culled, brushed and waxed, and sorted for size. Peaches are de-fuzzed during the brushing/waxing process. Fruit are packed into 25 lb boxes, and shipped immediately after harvest in refrigerated trucks or after short storage periods due to poor shelf life.

Storage
Peaches have a short shelf life of about 2 weeks under most conditions. They are not susceptible to chilling injury so can be stored at 31-32°F to maximize shelf life.

THE PEACH’S CONTRIBUTION TO DIET

Peaches have few marketing niches other than fresh and canned fruit. Freestone peaches are sold fresh, and clingstones are virtually all canned. About 98% of nectarines are marketed fresh. The utilization breakdown is as follows (% of USA peach crop): Fresh – 45-55% , Canned – 35-40%, Frozen – 5%. Per capita consumption is 9.5 lbs/year, considering peach and nectarine together.

Dietary value, per 100 gram edible portion

Water (%) 89
Calories 38
Protein (%) 0.6
Fat (%) 0.1
Carbohydrates (%) 10
Crude Fiber (%) 0.6
 % of US RDA*
Vitamin A 27
Thiamin, B1 1.4
Riboflavin, B2 3.1
Niacin 5.6
Vitamin C 15.6
Calcium 1.1
 Phosphorus 2.4
Iron 5.0
Sodium
Potassium 4.3

* Percent of recommended daily allowance set by FDA, assuming a 154 lb male adult, 2700 calories per day.