Choosing Among the 7500+ Cultivated Apple Species.

Apple trees, Malus spp., are native to the temperate zone of the Northern Hemisphere. Apples are the hardiest fruit trees, capable of withstanding extreme winter temperatures of below -40°C and have the highest chilling unit requirement of all fruit trees.

The genus Malus spp., in the family Rosaceae, is composed of about 32 to 57 species of deciduous trees and shrubs that includes the domesticated orchard apple, crab apples and wild apples.

Apple trees are cultivated worldwide and have been extensively bred for characteristics such as colour, shape, disease resistance, hardiness, taste and texture desirable for different uses.

Malus pumila, includes the eating apple, culinary apple and cider apple, now exists in over 7500 cultivars of apple trees.

Crabapples, used as pollenizers in apple orchards, rootstocks for increased hardiness in domestic apples and as ornamental trees with flowers for spring interest and fruits for winter interest and cold weather food for wildlife, are subdivided in 36 species and 4 natural hybrids.

Chilling units, expressed in chill hours is the minimum period of prolonged cold weather, ideally between temperatures of freezing point 0°C to 7°C, where maximum effect is achieved, a perennial fruit bearing plant has to be exposed to to successfully flower, through vernalization, for a productive harvest. The number of chilling hours needed by an apple tree varies by variety from 100 hours to above 1000 hours, with the most cold hardy cultivars requiring more chill hours to bloom.
Fruit trees that receive insufficient chilling hours in a given season will consequently blossom and leaf out poorly, at abnormal times, for inferior durations and may only bear a few fruits to none.
A deficiency of 50 to 100 chill units may result in a loss of up to 50% of a harvest. A deficiency of 250 chill units or more means a loss of a whole harvest.
Planting a low chilling apple cultivar in a high chill region risks a complete loss of crop when the early inflorescence, relative to cultivation zone, is damaged by spring frost. Open apple blossoms will be scorched by even a brief exposure to temperatures of -2°C and lower.
A high chilling apple cultivar planted in a low chill region will likely never flower and fruit.

Cross pollination by honey bees, mason bees, bumble bees, butterflies and other pollinators present in the orchard is crucial to seed and fruit flesh formation.

A seed count will provide an accurate evaluation of pollination. Well pollinated apples are visually of best quality and will have 7 to 10 seeds. Inadequate pollination will result in small and misshapen apples, slow to ripen that have fewer than 3 seeds, they will drop from the trees in the early summer without maturing.

• Self incompatible apples will not produce fruit when pollinated from flowers of the same tree or another tree of the same cultivar, they need to be planted in proximity of other different orchard apple, crap apple or wild apple varieties to allow for cross pollination.
• Self fertile apples will produce fruit independently but benefit from cross pollination in crop abundance.
• Triploid apples are sterile, their pollen cannot fertilize any other apple flowers including their own or other triploids. Triploid apple varieties need to be planted with at least two different diploid apple varieties to ensure adequate cross pollination for successful fruit set.

In apple orchards, alternate rows of different apple trees that flower at the same time are planted or a crabapple is planted or grafted onto an apple tree in a distance of every 7th tree.

Compatible apple varieties are apple cultivars that have been grouped by the time they flower so they can be planted together as cross pollinators to fertilize one another. Planting apple varieties that blossom around the same time together ensures that pollen is available when the flowers are receptive. 

Apple pollination groups are classified by their day of peak bloom in the average 30 day blossom period, depending on climate. 

Compatible pollenizers are selected from cultivars within the same group or a different group with a 6 day blooming overlap period.

Crab apples are altogether the best trees to pollinate most orchard apple pollination groups because they produce an abundance of pollen and flower over a longer flowering period.

In England, compatible apple cultivars are grouped by flowering dates.

In North America, compatible apple cultivars are grouped by flowering periods.

Apple seeds readily germinate into extreme heterozygote seedlings, also called pippin or kernel, with no resemblance to one another or their parents. Because apples are not true breeders when grown from seed, trees with selected characteristics are propagated by grafting young bud cuttings, called scions, onto rootstocks also chosen for desired characteristics.

Apple propagation by grafting has as advantages

• Precocity, the ability to fruit without the need to complete the juvenile phase, which is a natural state that lasts a few years that fruit seedlings must go through before becoming reproductive
• The ability to induce dwarfing for easier harvesting reach, efficient use of agricultural land and increase density and yield of fruit per acre.
• Ease of propagation as cuttings do not need to be rooted, instead they are grafted onto the rootstock of easily rooted plant.
• Increased cold tolerance from cold hardy rootstocks.
• Increased resistance to more pathogens, reducing the need for disease, virus, bacteria, fungi, pest and parasite control by a number of organic and non organic means.
• Ability to plant a particular variety in different soil types which it would not usually be adapted to.
• The addition of pollenizers by grafting limbs of crab apples onto trees at regular intervals down rows of tightly planted or unplanned, old apple orchards of a single variety.
• Top working, involving grafting new cultivars onto existing limbs of established trees to change the cultivar of an entire fruit orchard to a more profitable cultivar.

The scion provides 

• The leaf, flower and fruit characteristics; fruit quality, size, shape and skin and flesh colour, flavour and texture.
• Yield quantity.
• Above ground disease resistance.
• Storage potential of the fruit.
• Tree growth habit, vigour and growth patterns, upright or spreading, strength of the fruit bearing stems and being a lateral or stem bearer.
• Flowering and fruiting pattern and timing, annual or biennial fruit production and ripening time.

The rootstock determines

• The mature tree size; benchmarks 
• Winter hardiness and heat tolerance.
• Resistance to soil borne diseases and pests.
• The soil preference and adaptability of the resulting tree in order to match a plant to the soil in a particular field or orchard, whereby a scion is grafted onto a rootstock compatible with the soil, taking into consideration the pH, mineral content, water availability, salinity, sandiness, nematode population and pathogen load.
• Earlier or later flowering and fruiting for quicker returns on investments or to prevent susceptible flowers from being zapped by spring frosts.
• Yield efficiency; some rootstocks encourage the tree to channel more energy into fruit production instead of vegetative growth, increasing crop yields.
• Fruit size and productivity to a certain extent.
• Vigour and strength of the tree.

Key apple rootstocks under cultivation:

1. Geneva® Series (G)
   Developed by Cornell University and the USDA-ARS to provide superior resistance to fire blight, Phytophthora root rot and apple replant disease, offering high yield, efficiency for high density, productive orchards and consistent production. The rootstocks range from dwarfing to semi vigorous.
   
   G.41: Highly fire blight resistant, cold hardy, precocious, dwarfing apple rootstock.
   
   G.11: Very productive, cold hardy, resistant to fire blight, dwarf.
   
   G.210: Resistant to fire blight, woolly apple aphid, and replant disease, semi dwarf rootstock.
   
   G.935: Good for sandy soils, high disease resistance, semi dwarfing.
   
   
2. Malling (M)
   A series of classic, mostly apple rootstocks developed by the East Malling Research Station in England since 1912 to control tree size, increase productivity and provide disease resistance. Options range from severely dwarfing to vigorous, allowing for tailored orchard density and management.
   
   M.9 (including M.9 EMLA, M.9 NAKB 337 variations): Industry standard for high density planting, requires stalking support and good soil, highly susceptible to fire blight, dwarf rootstock.
   
   M.7 / M.7 EMLA: Excellent, sturdy, well anchored, cold hardy, semi dwarfing apple rootstock, free standing on good, deep soil, but highly prone to suckering.
   
   MM.106: Productive, but susceptible to collar rot in wet soils, semi dwarfing.
   
   MM.111 / EMLA 111: Very sturdy, drought tolerant, good for weak soils, vigorous, often used for larger, self supporting trees, shows high tolerance to woolly apple aphid and collar rot.
   
   M.25: Vigorous, used for large, standard trees.
   
   M.26: Produces a slightly larger tree than M.9, very productive, requires staking in early years, semi dwarfing.
   
   M.27: Used for very small trees, often as an inter stem or in high density vertical axis systems, very dwarfing.
   
   
3. Malling-Merton (MM)
   A result of collaborative breeding efforts between the East Malling Research Station and John Innes Institute in Merton, England for self supporting and vigorous rootstocks ideal for larger tree sizes and resistance to the woolly apple aphid
   
   MM.106: Semi dwarfing, highly productive rootstock, smaller than MM.111 but still produces a vigorous tree, adapted to a wide range of soils, must be planted in well drained soil due to susceptibility to collar rot.
   
   MM.102: Semi dwarfing rootstock, produces a medium sized tree with good anchorage, suitable for closer spacing.
   
   
4. EMLA
   Virus free selections of Malling stocks derived from material treated at the East Malling Research Station and Long Ashton Research Station, Washington State University to index and remove known viruses as a means of enhancing apple tree health thus vigour and longevity, controlling size and adaptation to specific soil conditions.
   
   EMLA 111: Known for its high vigor, deep roots, excellent anchorage, and tolerance to woolly apple aphids, collar rot and dry soils.
   
   EMLA 7 / M.7 EMLA: Semi dwarfing rootstock, cold hardy and adaptable to heavy or wet soils, though it may require support in certain conditions.
   
   EMLA 26: Dwarfing rootstock offering good cold hardiness to -40°F.
   
   EMLA 27: Highly dwarfing rootstock, ideal for small gardens and very high density plantings, requires strong support.
   
   
5. Budagovsky (B) or (Bud)
   Russian apple rootstock developed at the Michurinsk College of Agriculture renowned for exceptional cold hardiness, red pigmented foliage and wood allows for easy identification of suckers and graft failures, and high disease resistance, especially to collar rot and good tolerance to fire blight.
   
   B.9: Extremely cold hardy, fully dwarfing, resistant to collar rot, ideal for high density, trellis supported orchards, highly resistant to collar rot, fire blight and powdery mildew.
   
   B.118: Extremely winter hardy, very productive, highly vigorous, used for producing large, self well anchored trees, more precocious, bears fruit earlier, than seedling rootstocks.
   
   
6. Nic® 29 (RN 29 cv.)
   A virus cleaned selection from Belgium. Highly precarious and productive, full dwarfing apple rootstock, a Malling 9 clone but with greater vigour and a better developed root system and high resistance to collar rot and root rot.
   
   
7. Supporter 4 (Pi 80)
   German bred, semi dwarfing apple rootstock with excellent yield efficiency, high cold hardiness and fewer root suckers or burr knots. Suitable for high density, intensive and semi intensive planting systems. Developed in 1921 at the Pillnitz Research Station.
   
   
8. Autonovka
   Russian apple rootstock that produces vigorous, long lived, large, robust, drought tolerant, full size trees with better tolerance to wet soils than most rootstocks. Exceptionally cold resistant, suitable for harsh northern climates, hardy down to more extreme temperatures than -45°C.
   
   
9. NAKB (T)
   A widely used, virus free, dwarfing rootstock clone derived from M.9 for apple trees originating from the Netherlands. Considered a standard for intensive, high density orchards due to its high yield efficiency. Requires permanent trellis support and well drained soil. Resistant to collar rot, but highly susceptible to fire blight and not highly cold hardy. Highly precocious, fruits early, and produces large apples.
   
   
10. Pajam®1 Lancep
    French clonal M.9, dwarfing apple rootstock, a selection of Paradis jaune de Metz, very precocious, productive, and produces high quality fruit, with good uniformity, well suited for intensive, high density plantings and requires support. Resistant to fire blight and collar rot.
    
    
11. Pajam®2 Cepiland
    Another strong French M.9 clone, dwarfing apple rootstock known for high productivity, early bearing and good fruit colour. With added vigour the rootstock makes for suitable high density orchard planting of 1 600 to 4 000 trees per ha, requiring support. Performs well on replant sites and is moderately tolerant to woolly apple aphids and lime. Often used to improve fruit size and colour.
    
    
12. Seedling
    Seedling rootstocks provide a vigorous, hardy and large foundation for fruit trees, particularly apples, resulting in full sized 100% standard trees that are free standing, long lived and resistant to cold.
    
    

All the cultivated domesticated apples, Malus domestica, are derived from the wild apple species Malus sieversii, native to the mountains of Central Asia, the primary ancestor, originating 46% of the modern apple genome. They hybridized with other wild apple species, including the European crabapple Malus sylvestris, Malus baccata and Malus orientalis, which contributed to the diversity of apples today. Due to habitat loss, Malus sieversii is now listed as a vulnerable species.

Old apple cultivars and species are considered heritage apple varieties when they have a long known cultivation or foraging history often predating commercial orchards and heirloom apple cultivars when they have been passed down through generations of gardeners and farmers. Old apple varieties taste better with more complex intrinsic flavours than modern apples that have been bred to resist diseases, tree shape and size and fruit appearance.

Apple seedlings apple trees grown from seed. They are genetically unique, often highly adaptable and develop deep taproots, making them vigorous growers, frequently exhibiting a wild, bushy growth habit and do not produce the same apple variety as their parents.

Keep an eye out on our apple plant collection as we bring you the largest selection of apple trees, scions and rootstocks available worldwide, from the most cold hardy varieties to those adaptable to the warmest southern weather.

Plant wild apple species, heritage varieties, heirloom cultivars and seedlings to conserve and encourage biodiversity in nature, crucial for resilience and stability of whole ecosystems against environmental changes, diseases and climate change. Plant diversity yields a multitude of fruit colour, texture, shape and taste. A diverse biosphere ensures healthy soils, pollination, pest control and nutritional benefits.