Almond (Amygdalus communis L.)

Almond, scientifically known as Amygdalus communis L. (synonym Prunus dulcis), is an important stone fruit species with ancient origins in Central and Western Asia. Since then, it has spread to various regions including China, India, Iran, Syria, and Mediterranean countries. Almonds are valued for their edible kernels and are cultivated worldwide in temperate climates. Türkiye ranks among the world’s leading almond producers, following the United States, Spain, Italy, Iran, Morocco, and Syria.

Almond (Pexels)

Botanical and Morphological Characteristics

Almond trees can grow as shrubs or reach heights of up to 10 meters, with either upright or spreading habits. The trunk is typically grayish-reddish brown. Branches are grayish-brown and densely branched. Leaves are long, lanceolate, and glossy dark green.

Almond flowers exhibit typical characteristics of the Rosaceae family: five sepals, five petals, twenty stamens, and one pistil. Petals are usually pinkish-red with prominent dark veins. The ovary contains two ovules, but typically only one develops into the kernel; if both develop, a “double almond” is formed. Rarely, the development of two ovaries results in “twin almonds” with no commercial value. Almonds have a chromosome number of n=8. Pollination is primarily carried out by bees. Most almond varieties are self-incompatible, and mutual incompatibility between varieties may occur, requiring the planting of at least two compatible varieties for successful fruit set.

Botanically, the almond fruit is a drupe, like peach and apricot. However, because the kernel is consumed, almonds are commercially classified among nut fruits.

Almond Varieties

Almonds are generally divided into two pomological groups:

Bitter Almonds

These contain amygdalin, which converts to toxic hydrocyanic (prussic) acid when consumed in significant quantities. Bitter almonds are primarily used for oil extraction.

Sweet Almonds

These contain very little or no amygdalin. Sweet almonds are further classified by shell hardness:

• Hand Almonds (Paper-shell): Have very thin shells and kernel yields can reach up to 70%. Storage can be difficult.
• Tooth Almonds (Soft-shell): Can be easily cracked by hand or teeth, with kernel yields around 50%. Storage is also problematic. Hand and tooth almonds are sometimes grouped together.
• Hard-shell Almonds: Difficult to crack by hand, with kernel yields up to 40%.
• Stone Almonds: Have very thick and hard shells, resulting in low kernel yields (18–30%). Hard and stone almonds have low kernel yields.

Desirable shell characteristics include moderate hardness—not too hard or too soft—and a well-closed suture line. For the kernel, a light color, smooth (non-wrinkled), and hairless surface is preferred.

Ecological Requirements

Almond Tree Fooled by False Spring (AA)

Climate

Almond is well suited to temperate climates, particularly the Mediterranean climate characterized by mild, wet winters and hot, dry summers. Trees can withstand winter temperatures as low as −25°C, but flower buds may be damaged below −18°C. Almond requires a chilling requirement of approximately 300–500 hours below 7.2°C.

Spring frosts are a major limiting factor in almond cultivation because almonds bloom earlier than most other temperate fruit trees. Fully opened almond flowers can withstand temperatures as low as −4.4°C for a short time; this tolerance drops to −2.2°C once petals begin to fall, and young fruits may be damaged at −0.6°C to −1°C. To reduce frost risk, orchards should be planted on slopes where cold air can drain, and varieties with late flowering and long blooming periods should be selected.

High temperatures over a period of 6–8 months from flowering to harvest are necessary for fruit maturation. Almond is relatively drought-tolerant among fruit crops. However, annual rainfall of 500–600 mm or supplemental irrigation improves yield and fruit quality. Rain during flowering can negatively affect pollination and increase disease incidence. Rain just before harvest is undesirable as it reduces fruit quality.

Soil

Almond is not highly selective regarding soil type and can grow well in dry, stony, gravelly, and calcareous soils where other fruit trees struggle. However, it prefers deep, well-drained soils. Sandy-loam soils generally yield the best results. Almonds do not tolerate excessive soil moisture or fluctuating groundwater tables. Dry, gravelly, sandy soils should be improved with organic matter. Almond has a nitrogen requirement comparable to peach. Nutrient deficiencies can lead to weak tree growth, poor fruit set, and wrinkled, underfilled kernels.

Propagation and Rootstocks

Propagation

Almond can be propagated sexually (by seed) or vegetatively. Seed propagation is used for breeding, orchard establishment, and rootstock production. For commercial nursery production, dormant T-budding is a common method. In regions with mild winters, bud grafting is preferred. In dry areas, grafting must be done early because sap flow begins early. In hot regions such as Türkiye’s GAP region, grafting is often delayed until September when temperatures are relatively lower; in such cases, chip budding is preferred because the bark may not peel easily. For changing varieties in mature trees, cleft grafting or bark grafting (shepherd grafting) is commonly used.

Rootstocks

Rootstock selection depends on compatibility with the scion variety, soil conditions, water availability, and the presence of soil-borne pests such as crown gall and nematodes.

• Almond Seedlings (Seed Rootstocks): The most suitable rootstock for almond, especially in deep, well-drained, non-irrigated, and calcareous soils. They ensure good compatibility and produce vigorous, long-lived trees. Seedlings from bitter almonds are reported to be highly resistant to the capnodis pest (root collar borer) and perform well under dry conditions. However, almond rootstocks are generally susceptible to crown gall and nematodes. Seeds from varieties such as Texas, Cristomorto, and Desmayo produce uniform and vigorous seedlings. Almond seeds require 3–4 weeks of cold stratification at 0–5°C for good germination.

• Peach Seedlings (Seed Rootstocks): Used in areas with adequate rainfall or irrigation on alluvial or sandy-loam soils. Nemaguard is used in nematode-infested soils. Peach rootstocks encourage earlier fruiting but produce shorter-lived trees than almond rootstocks. Compatibility with almond scions is generally poor, leading to swelling at the graft union and yield decline after 10–12 years. Unsuitable for calcareous, dry, or high-boron soils. Highly susceptible to viruses.

• Almond × Peach Hybrids: Hybrids such as GF 677 are widely used and adaptable to various soil conditions. GF 677 is especially popular due to vigorous growth, early fruiting, high yield, and tolerance to calcareous soils (chlorosis resistance). It is propagated vegetatively. However, GF 677 performs poorly in heavy, poorly drained soils.

• GN Series (Garnem, Felinem): These are complex hybrids (e.g., Myrobalan plum × peach × almond). Garnem (GN 15) is the most common. Due to Myrobalan plum parentage, they show better tolerance than GF 677 to heavy soils and poor drainage and are resistant to crown gall nematodes. They also provide vigorous growth.

• Plum Rootstocks: Can be used in heavy, poorly drained, or root rot-prone soils. However, compatibility with almond is generally poor, leading to low yield, fruit quality problems (adherent shells), and short-lived trees. Examples of commonly used plum clonal rootstocks are Marianna 2624 and Marianna GF 8-1.

• Apricot Rootstocks (Zerdali Rootstocks): Apricot adapts to similar soil conditions as almond and is nematode-resistant. Although initial growth is good, later incompatibility problems arise, causing breakage at the graft union. Not widely used in practice.

Orchard Establishment and Annual Management Practices

Orchard Establishment

Commercial almond orchards can be established using grafted saplings or, especially in dry, non-irrigated areas, by direct seeding followed by in-place grafting. Grafted saplings are preferred for irrigated land. For optimal yield and quality, orchards should be established in soils approximately 2 meters deep, fertile, and permeable.

Due to self-incompatibility, orchards must be planted with at least two mutually compatible varieties. Pollinator varieties must have overlapping flowering periods with the main variety. Planting patterns may include two rows of the main variety followed by one row of the pollinator, or two rows each of two compatible main varieties. Beehives are essential for effective pollination (e.g., one hive per 5 decares or 5–8 hives per 10 decares). Bees become active when air temperature exceeds 12°C.

Planting distances vary depending on variety, rootstock, ecological conditions, and planned management, ranging from 3×3 m to 6×6 m, or up to 7×9 m in fertile soils. In dry areas, wider spacing allows for root spread; in irrigated areas, canopy size determines spacing. In regions with mild winters, autumn planting is preferred; in areas with harsh winters, spring planting is recommended. Because almond root systems are sparse and sensitive, using container-grown saplings can reduce transplant shock and improve survival rates.

Soil Management

In spring, orchards are typically disked to incorporate winter weeds into the soil. A light harrowing before harvest facilitates the collection of fallen almonds. Autumn tillage helps retain winter moisture. In areas with crown gall problems, soil cultivation should be shallow to avoid root injury; hand hoeing may be necessary when required.

Irrigation

Contrary to a common misconception, almond trees benefit significantly from irrigation. Regular irrigation increases yield and fruit quality and facilitates shell splitting. Two or three supplemental irrigations during the growing season, especially under low rainfall conditions, enhance growth and yield. Irrigation should be avoided immediately before harvest. Drip irrigation is an efficient method that conserves water and enables fertigation. Under irrigated conditions, yields can be two to three times higher than under non-irrigated conditions, and kernels are larger.

Fertilization

Fertilization practices should be based on soil analysis results. Nitrogen is particularly important for growth and yield; a general recommendation is 10–25 kg of pure nitrogen per decare. Farmyard manure is also beneficial for improving soil structure and fertility. In Türkiye’s Southeastern Anatolia Project (GAP) region, soils are generally poor in organic matter, high in clay and lime content, and have high pH, reducing the availability of phosphorus and zinc to plants.

Pruning

Almond does not require excessive pruning. Regular removal of dead, crossing, or inward-growing branches and thinning to allow light penetration into the canopy is beneficial. For shaping young trees, the modified central leader system is commonly used. From the third year onward, annual shoots can be shortened (e.g., to 40–50 cm) and crowded branches removed. Almond bears fruit on annual shoots and spur clusters (bouquets). Annual pruning is necessary in bearing trees, but severe pruning should be avoided. Renewal pruning may be needed after 15–20 years. Pruning is generally done in autumn in mild regions and late winter (February) in cold regions, after most leaves have fallen.

Almond Varieties

Native Turkish Selections/Varieties

In Türkiye, particularly in the Aegean Region, several promising native almond types have been identified through selection programs. Some examples are:

• 48-1: Flowers early, requires a pollinator (Akbadem, 48-3, Hacı Alibey). Kernel weight is 1.50 g, yield is 37.97%. Can also be consumed as green almond.

• Akbadem (48-2): Has vigorous trees, flowers early, and is a hand almond. Pollinators are 48-1, 48-3, 48-4, and Hacı Alibey. Kernel weight is 1.80 g, yield is 35.17%. Very high yield. Excellent quality as both green almond and kernel.

• Hacı Alibey (48-5): Forms medium-vigorous trees, very early flowering. Pollinators are 48-1, 48-3, 48-4, and Akbadem. Kernel weight is 1.15 g, yield is 35.17%. Very high yield.

• Gülcan 1 (101-23): Forms medium-vigorous trees, nomad^【1】 variety. Pollinators are 101-9 and 101-13. Kernel weight is 0.85 g, yield is 27.96%. Resistant to almond branch cancer. Belongs to the stone almond group.

• 101-9: Forms vigorous trees, late flowering. Pollinators are 101-13 and Gülcan 1. Kernel weight is 1.02 g, yield is 31.88%.

• 101-13: Forms vigorous trees, late flowering. Pollinators are 101-9 and Gülcan 1. Kernel weight is 0.95 g, yield is 26.10%. Does not produce double almonds. Ripens relatively late. Belongs to the stone almond group.

Foreign Almond Varieties

• Cristomorto: Forms vigorous trees, late flowering. Pollinators are Rachele and Texas. Kernel weight is 1.6 g, yield is 36%. Resistant to crown rot. Ripens late.

• Drake: Forms medium-sized trees, mid-to-late flowering. Pollinators are Marcona, Nonpareil, and Peerless. Kernel weight is 1.2 g, yield is 46%. Susceptible to Monilia and necrosis.

• Ferraduel: Forms vigorous trees, late flowering. Pollinators are Ai, Ferragnes, Filippo Ceo, Tuono, and Texas. Kernel weight is 1.3 g, yield is 28%. Resistant to Monilia, susceptible to necrosis. Ripens late.

• Ferragnes: Forms medium-vigorous trees, late flowering. Pollinators are Ai, Cristomorto, Ferraduel, Ferrastar, Filippo Ceo, Tuono, and Texas. Kernel weight is 1.5 g, yield is 41%. Does not produce double almonds. Moderately resistant to Monilia. Ripens late. Hard-shell almond.

• Nonpareil: Forms medium-vigorous trees, late flowering. Hand almond. Pollinators are Desmayo largueta, Drake, Marcona, and Ne Plus Ultra. Kernel weight is 1.4 g, yield is 60–70%. Susceptible to Monilia and bud drop.

• Texas (Mission): Forms vigorous trees, late flowering. Pollinators are Cristomorto, Ferraduel, Ferragnes, and Tuono. Kernel weight is 1.5 g, yield is 50%. Susceptible to Monilia. Ripens late. Belongs to the tooth almond group.

• Tuono: Forms vigorous trees, late flowering, and is self-compatible (highly productive). Pollinators are Ferraduel, Ferragnes, and Texas. Kernel weight is 1.6 g, yield is 41%. Medium-early ripening. Susceptible to necrosis.

• Picantili: Forms vigorous trees, late flowering. Pollinators are Ferraduel, Ferrastar, and Genco. Kernel weight is 1.6 g, yield is 46%. Resistant to Monilia.

• Genco: Forms vigorous trees, late flowering, and is self-compatible. Pollinators are Ferrastar, Filippo Ceo, Tuono, and Texas. Kernel weight is 1.2 g, yield is 35%. Very high productivity.

Diseases and Pests

Almonds are susceptible to various diseases and pests. Common diseases include:

• Peach Leaf Curl (Klok - Taphrina deformans): Causes thickening and distortion of leaves, flowers, fruits, and young shoots.

• Shot Hole (Çil - Coryneum beijerinckii): Produces reddish-brown spots on leaves that later fall out, leaving holes. Also affects shoots, buds, flowers, and fruits.

• Red Leaf Spot (Polystigma ochraceum): Characterized by reddish, raised lesions on leaves.

• Powdery Mildew (Sphaerotheca pannosa): Appears as a white powdery coating on leaves and shoots; can also affect fruit.

Common pests include:

• Mites: Various species feed on leaves, causing discoloration and premature leaf drop.

• Peach Aphid (Myzus persicae): Feeds on young shoots and leaves and can transmit viruses.

• Root Collar Borer (Kapnodis - Capnodis tenebrionis): Larvae tunnel in roots and root collar, particularly drying out young trees. Weaker trees are more susceptible.

• Bark Beetles (Scolytus spp.): Tunnel into wood and bark, disrupting nutrient flow, weakening or killing branches and trees. Typically attack weakened trees.

For current pest and disease management recommendations, consult local agricultural extension services, as pesticide regulations and efficacy may vary.

Harvest and Post-Harvest Operations

Almond Cultivation in Elazığ (AA)

Determining Harvest Time

Maturity is indicated by the drying, leathery texture, and splitting of the outer green hull. Harvest should not begin until the green hulls of inner fruits begin to open.

• Early Harvest: Makes shaking and stripping difficult, hinders removal of the green hull, and results in underdeveloped, wrinkled, and shriveled kernels upon drying.

• Delayed Harvest: Almonds fall naturally to the ground, making collection difficult, increasing bird and insect damage, and causing kernel darkening in rainy or foggy weather.

Harvest Methods

Almonds are generally harvested by striking branches with poles or by shaking. Rubber-tipped mallets on poles minimize tree damage. Tarps are spread under trees to facilitate collection. In commercial orchards, mechanical shakers and collectors are used. Carbon-fiber rakes, hand-operated and battery-powered harvesters, efficiently and rapidly dislodge fruits without damaging flower buds.

Hull Removal (Dehulling)

Harvested fruits must be dehulled immediately. Delayed dehulling can lead to insect infestation and mold, and darken the kernel. Ease of hull removal is an important heritable trait. Hulls are separated manually or mechanically. If hulls are very dry, moistening almonds can facilitate separation. It has been successfully adapted to use modified hazelnut shelling machines with enlarged holes for almond dehulling.

Drying

Dehulled almonds dry easily in open air during autumn months, provided they are not piled and are occasionally turned. If available, drying facilities used for other crops can also be utilized. Drying should be done quickly. The kernel is sufficiently dried when it snaps rather than bends when bent.

Blanching

If sold in-shell, almonds are bleached to achieve a uniform light yellow shell color. Bleaching is done using sulfur dioxide gas. For 100 kg of in-shell almonds, 50–150 g of sulfur flowers are burned. Bleaching lasts 10–30 minutes and does not reduce internal quality. However, prolonged exposure or high concentration to darken almonds can alter taste, imparting a soapy flavor.

Cracking and Grading

Almond kernels sold shelled are cracked by producers or sellers. Cracking is done manually or mechanically. One worker can crack 8–10 kg of almonds by hand per day. Cracked kernels should be dried in a cool, shaded place (not in direct sunlight). Grading kernels through sieves enables more stable marketing and higher income for producers.

Storage

Properly dried in-shell almonds can be stored for up to six months in cool, dry storerooms. Hard-shell storage is most suitable. In cold storage at 0°C and 70–75% humidity, in-shell or shelled almonds can be stored for one to two years. They should be fumigated and placed in storage under appropriate conditions.

Yield

Yield in almond orchards is generally expressed as the weight of in-shell fruit or, in modern production, as the amount of kernel per unit area (decare or hectare). Kernel yield is calculated as: Kernel Yield (%) = (Kernel Weight / In-Shell Fruit Weight) × 100. This ratio varies with shell thickness; for example, Nonpareil (thin-shell) has a kernel yield of 60–70%, while Ferragnes (medium-thick shell) has about 40%.

In irrigated bearing orchards, 2000–3000 kg of green hull almonds per decare are obtained, depending on variety. This corresponds to approximately 6.6–9.0% kernel yield. In California (USA), irrigated orchards yield about 200 kg of kernel per decare. Modern almond orchards in Türkiye achieve similar yields. While some sources report yields of up to 300 kg of kernel per decare, current cultivation techniques make this level difficult to achieve. Therefore, for economic analyses, it is more realistic to estimate a maximum of about 200 kg of kernel per decare under optimal conditions as trees mature. In non-irrigated orchards, yields reach only 60–70 kg of kernel per decare. In addition to yielding at least two to three times more than non-irrigated orchards, irrigated orchards produce larger and more attractive kernels.