Thealmond(Prunus dulcis,syn.Prunus amygdalus) is a species of tree native to theMiddle East, theIndian SubcontinentandNorth Africa."Almond" is also the name of the edible and widely cultivatedseedof this tree. Within the genusPrunus, it is classified with thepeachin the subgenusAmygdalus, distinguished from the other subgenera by the corrugated shell (endocarp) surrounding the seed.The fruit of the almond is adrupe, consisting of an outer hull and a hard shell with the seed, which is not atrue nut, inside. Shelling almonds refers to removing the shell to reveal the seed. Almonds are sold shelled or unshelled.Blanchedalmonds are shelled almonds that have been treated with hot water to soften theseedcoat, which is then removed to reveal the whiteembryo.Description[edit]Tree[edit]The almond is adeciduoustree, growing 4–10m (13–33ft) in height, with a trunk of up to 30cm (12in) in diameter. The youngtwigsare green at first, becoming purplish where exposed to sunlight, then grey in their second year. Theleavesare 3–5inches long,[3]with a serrated margin and a 2.5cm (1in)petiole. Theflowersare white to pale pink, 3–5cm (1–2in) diameter with five petals, produced singly or in pairs and appearing before the leaves in early spring.[4][5]Almond grows best in Mediterranean climates with warm, dry summers and mild, wet winters. The optimal temperature for their growth is between 15 and 30°C (59 and 86°F) and the tree buds have a chilling requirement of 300 to 600 hours below 7.2°C (45.0°F) to break dormancy.[6]Almonds begin bearing an economic crop in the third year after planting. Trees reach full bearing five to six years after planting. The fruit matures in the autumn, 7–8 months after flowering.[5][7]Drupe[edit]The almond fruit measures 3.5–6cm (1–2in) long. In botanical terms, it is not anut, but adrupe. The outer covering orexocarp, fleshy in other members ofPrunussuch as theplumandcherry, is instead a thick, leathery, grey-green coat (with a downy exterior), called the hull. Inside the hull is a reticulated, hard, woody shell (like the outside of a peach pit) called theendocarp. Inside the shell is the edible seed, commonly called a nut. Generally, one seed is present, but occasionally two occur.Origin and history[edit]Harvesting of the almond crop atQand-i Badam,Fergana Valley(16th century)[8]The almond is native to theMediterranean climateregion of the Middle East, eastward as far as theYamuna RiverinIndia.[9]In Iran, India, Afghanistan, Azerbaijan and other Central Asian countries, it is known asbādām. It was spread by humans in ancient times along the shores of the Mediterranean into northern Africa and southern Europe, and more recently transported to other parts of the world, notably California, United States.[9]The wild form of domesticated almond grows in parts of theLevant. The fruit of the wild forms contains theglycosideamygdalin, "which becomes transformed into deadly prussic acid (hydrogen cyanide) after crushing, chewing, or any other injury to the seed."[10]Wild almonds are bitter, the kernel produces deadly cyanide upon mechanical handling[clarification needed], and eating even a few dozen in one sitting can be fatal. Selection of the sweet type, from the many bitter types in wild, marked the beginning of almond domestication. How humans selected the sweet type remains a mystery.[11]It is unclear as to which wild ancestor of the almond created the domesticated species. Ladizinsky suggests the taxonAmygdalus fenzliana(Fritsch) Lipsky is the most likely wild ancestor of the almond in part because it is native of Armenia and western Azerbaijan where it was apparently domesticated.While wild almond species are toxic, domesticated almonds are not;Jared Diamondargues that a common genetic mutation causes an absence of amygdalin, and this mutant was grown by early farmers, "at first unintentionally in the garbage heaps, and later intentionally in their orchards".[12]Zohary and Hopf believe that almonds were one of the earliest domesticatedfruit treesdue to "the ability of the grower to raise attractive almonds from seed. Thus, in spite of the fact that this plant does not lend itself to propagation from suckers or from cuttings, it could have been domesticated even before the introduction ofgrafting".[10]Domesticated almonds appear in theEarly Bronze Age(3000–2000 BC) such as the archaeological sites of Numeria (Jordan),[11]or possibly a little earlier. Another well-known archaeological example of the almond is the fruit found inTutankhamun's tomb in Egypt (c. 1325 BC), probably imported from the Levant.[10]Of the European countries that the Royal Botanic Garden Edinburgh reported as cultivating almonds, Germany[13]is the northernmost, though the domesticated form can be found as far north as Iceland.[14]Etymology and names[edit]The word "almond" comes from Old Frenchalmandeoralemande,Late Latin*amandula, derived through a formamygdalafrom the Greek ἀμυγδαλή (amygdalē) (cf.amygdala), an almond.[15]Theal-in English, for thea-used in other languages may be due a confusion with theArabicarticleal, the word having first dropped thea-as in the Italian formmandorla; the British pronunciationah-mondand the modern Catalanametllaand modern Frenchamandeshow a form of the word closer to the original. Other related names of almond includeMandelorKnackmandel(German),mandorlo(Italian for the tree),mandorla(Italian for the fruit),amêndoa(Portuguese), andalmendra(Spanish).[16]The adjective "amygdaloid" (literally "like an almond") is used to describe objects which are roughly almond-shaped, particularly a shape which is part way between atriangleand anellipse. See, for example, thebrain structureamygdala, which uses a direct borrowing of the Greek termamygdalē.[17]Production[edit]World production of almonds was 2.9milliontonnesin 2013, with United States as the largest producer of 1.8million tonnes.[18]Top producers of almonds (with shell) in 2013[18]CountryProduction(million tonnes)USA1.8Australia0.16Spain0.15Morocco0.1Iran0.09World2.92In the United States, production is concentrated in California, with almonds being California's third-leading agricultural product, its top agricultural export in 2008,[19]and 100% of the U.S. commercial supply. The United States is the dominant supplier of almonds. Almonds are mostly exported as shelled almonds (70%), with the remainder being either unshelled or processed.[20]In 2015,environmental problemsin California affected the almond supply, contributing to higher almond prices worldwide. Rising demand for almonds has also contributed to higher prices worldwide and increased production in California.[21][22]Australia is the largest almond production region in theSouthern Hemisphere, and second largest producing country. In 2013, Australia produced 9% of the world almond supply (table). Most of the almond orchards are located along theMurray Rivercorridor in New South Wales, Victoria, and South Australia.[23][24]Spain has one of the most diverse commercial cultivars of almonds.[25]It is grown in Spain's Catalonia, Valencia, Murcia, Andalusia, and Aragón regions and the Balearic Islands.[26]In Greece, most of the production comes from the region ofMagnesiaat the area ofAlmyros. The most cultivated types of almonds in Greece are 'Ferragnes' and 'Texas' ('Mission'), which are known for their sweet taste and premium quality. Because of its quality, it is used as a luxury nut. In Turkey, most of the production comes from the Aegean, Marmara, and Mediterranean regions.[27]Pollination[edit]Young almond fruitMature almond fruitThepollinationof California's almonds is the largest annualmanaged pollinationevent in the world, with close to one million hives (nearly half of allbeehivesin the USA) being trucked in February to the almond groves. Much of the pollination is managed by pollination brokers, who contract with migratorybeekeepersfrom at least 49 states for the event. This business has been heavily affected bycolony collapse disorder, causing nationwide shortages of honey bees and increasing the price ofinsect pollination. To partially protect almond growers from the rising cost of insect pollination, researchers at theAgricultural Research Service(ARS) have developed a new line ofself-pollinatingalmond trees.[28]Self-pollinating almond trees, such as the 'Tuono', have been around for a while, but their harvest is not as desirable as the insect-pollinated California 'Nonpareil' almond tree. The 'Nonpareil' tree produces large, smooth almonds and offers 60–65% edible kernel per nut. The 'Tuono' has thicker, hairier shells and offers only 32% of edible kernel per nut, but having a thick shell has advantages. The 'Tuono's' shell protects the nut from threatening pests such as thenavel orangeworm. ARS researchers have managed to crossbreed the pest-resistant 'Tuono' tree with the 'Nonpareil', resulting inhybridizedvarieties of almond trees that are self-pollinated and maintain a high nut quality.[29]The new, self-pollinating hybrids possess quality skin color, flavor, and oil content, and reduce almond growers' dependency on insect pollination.[28]Diseases[edit]Main article:List of almond diseasesAlmond trees can be attacked by an array of damaging organisms, including insects, fungal pathogens, plant viruses, and bacteria.[30]Sweet and bitter almonds[edit]Flowering (sweet) almond treeBlossom on bitter almond treeThe seeds ofPrunus dulcisvar.dulcisare predominantly sweet,[31][32]but some individual trees produce seeds that are somewhat more bitter. The genetic basis for bitterness involves a single gene, the bitter flavour furthermore beingrecessive,[33][34]both aspects making this trait easier to domesticate. The fruits fromPrunus dulcisvar.amaraare always bitter, as are the kernels from otherPrunusspecies, such as peach and cherry (to a lesser extent).The bitter almond is slightly broader and shorter than the sweet almond, and contains about 50% of th