Stone Fruits

Peach

History of peaches

Although its botanical name Prunus persica suggests the peach is native to Persia, it actually originated in China where it has been cultivated since the early days of Chinese culture. Peaches were mentioned in Chinese writings as far back as the tenth century BC and were a favored fruit of emperors.

Its English name derives from the Latin plural of persicum malum, meaning Persian apple. In Middle English, it melded into peche, much closer to what we call it today.

The Persians brought the peach from China and passed it on to the Romans. The peach was brought to America by Spanish explorers in the sixteenth century and eventually made it to England and France in the seventeenth century, where it was a prized albeit rare treat.

A horticultist by the name of George Minifie supposedly brought the first peaches from England to the USA in the early seventeenth century, planting them at his Estate of Buckland in Virginia.

Various American Indian tribes are credited with spreading the peach tree across the United States, taking seeds along with them and planting as they roved the country.

Although Thomas Jefferson had peach trees at Monticello, United States farmers did not begin commercial production until the nineteenth century in Maryland, Delaware, Georgia and finally Virginia. California grows 65% of peaches grown for commercial production in the United States², but the northern states, Colorado, Michigan, and Washington also grow a significant amount. Italy, China and Greece are major producers of peaches outside of the United States.

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Cultivation

Peach plants grow very well in a fairly limited range, since they have a chilling requirement that tropical areas cannot satisfy, and they are not very cold-hardy. The trees themselves can usually tolerate temperatures to around ?26 °C to ?30 °C, although the following season’s flower buds are usually killed at these temperatures, leading to no crop that summer. Flower bud kill begins to occur between ?15 °C and ?25 °C depending on the cultivar (some are more cold-tolerant than others) and the timing of the cold, with the buds becoming less cold tolerant in late winter.³ Certain cultivars are more tender and others can tolerate a few degrees colder. In addition, a lot of summer heat is required to mature the crop, with mean temperatures of the hottest month between 20 °C and 30 °C. Another problematic issue in many peach-growing areas is spring frost. The trees tend to flower fairly early in spring. The blooms often can be damaged or killed by freezes; typically, if temperatures drop below about ?4 °C, most flowers will be killed. However, if the flowers are not fully open, they can tolerate a couple of degrees colder.

Important historical peach-producing areas are China, Iran, France, and the Mediterranean countries like Italy, Spain and Greece. More recently, the United States (where the three largest producing states are California, South Carolina⁴, and Georgia⁵), Canada (British Columbia), and Australia (the Riverland region) have also become important; peach growing in the Niagara Peninsula of Ontario, Canada, was formerly intensive but ended in 2008 when the last fruit cannery in Canada was closed by the proprietors. Oceanic climate areas like the Pacific Northwest and coastline of North Western Europe are generally not satisfactory for peach-growing due to inadequate summer heat, though they are sometimes grown trained against south-facing walls to catch extra heat from the sun. Trees grown in a sheltered and south-facing position in the southeast of England are capable of producing both flowers and a large crop of fruit.

For home gardeners, semi-dwarf (3 to 4 m) and dwarf (2 to 3 m) varieties have been developed by grafting desirable cultivars onto dwarfing rootstock. Fruit size is not affected. Another mutation is flowering peaches, selected for ornamental display rather than fruit production.

Depending on climate and cultivar, peach harvest can occur from late May into August; harvest from each tree lasts about a week.

Nectarines

The nectarine is a cultivar group of peach that has a smooth, fuzzless skin. Though fuzzy peaches and nectarines are commercially regarded as different fruits, with nectarines often erroneously believed to be a crossbreed between peaches and plums, or a “peach with a plum skin”, they belong to the same species as peaches. Several genetic studies have concluded in fact that nectarines are created due to a recessive gene, whereas a fuzzy peach skin is dominant.⁶ Nectarines have arisen many times from peach trees, often as bud sports.

As with peaches, nectarines can be white or yellow, and clingstone or freestone. On average, nectarines are slightly smaller and sweeter than peaches, but with much overlap.⁶ The lack of skin fuzz can make nectarine skins appear more reddish than those of peaches, contributing to the fruit’s plum-like appearance. The lack of down on nectarines’ skin also means their skin is more easily bruised than peaches.

The history of the nectarine is unclear; the first recorded mention in English is from 1616,⁷ but they had probably been grown much earlier within the native range of the Peach in central and eastern Asia.

Planting

The developmental sequence of a nectarine over a 7½ month period, from bud formation in early winter to fruit ripening in midsummer (see image page for further information)

Most peach trees sold by nurseries are named cultivars grafted onto a suitable rootstock. It is also possible to grow a tree from either a peach or nectarine seed, but the fruit quality of the resulting tree will be very unpredictable.

Peaches should be located in full sun, and with good air flow. This allows cold air to flow away on frosty nights and keeps the area cool in summer. Peaches are best planted in early winter, as this allows time for the roots to establish and be able to sustain the new spring growth. When planting in rows, plant north-south.

For optimum growth, peach trees require a constant supply of water. This should be increased shortly before the harvest. The best tasting fruit is produced when the peach is watered throughout the season. Drip irrigation is ideal, at least one dripper per tree. Although it is better to use multiple drippers around the tree, this is not necessary. A quarter of the root being watered is sufficient.

Peaches have a high nutrient requirement, needing more nitrogen than most other fruit trees. An NPK fertilizer can be applied regularly, and an additional mulch of poultry manure in autumn soon after the harvest will benefit the tree. If the leaves of the peach are yellow or small, the tree needs more nitrogen. Blood meal and bone meal, 3–5 kg per mature tree, or calcium ammonium nitrate, 0.5–1 kg, are suitable fertilisers. This also applies if the tree is putting forth little growth.

If the full amount of peaches is left, they will be under-sized and lacking in sugar and flavour. In dry conditions, extra watering is important. The fruit should be thinned when they have reached 2 cm in diameter, usually about 2 months after flowering. Fresh fruit are best consumed on the day of picking, and do not keep well. They are best eaten when the fruit is slightly soft, having aroma, and heated by the sun.

Storage

Hard fruit can be softened at home at room temperature, though it may not get any sweeter. The process is facilitated by ethylene, similar to the ripening of bananas. Storage in a paper bag concentrates this gas and hastens the process.⁸ When the fruit is soft, it can be stored in the refrigerator for a few days to slow further changes.

In the August 13, 2004 edition of the Journal of Experimental Botany, researchers found that peaches stored around 40 °F (4 °C) became mealy and discolored.⁹

After slicing, peaches exhibit enzymatic browning; ascorbic acid, usually in the form of lemon juice, is added to delay the process, and the flavors are complementary. Peaches also can be frozen, and can be blanched to inhibit enzymatic changes in texture. Peaches often are canned, both commercially and at home; added sugars and acids reduce the retort or pressure cooking time which reduces excessive softening.

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