Fruit Fact: Apple, a type of Pome Fruit
Introduction: The botanical name for the cultivated apple is Malus domestica. However, recent research suggests that there is little distinction in between the cultivated apple and malus sieversii, which is found growing wild in the mountains of Central Asia in southern Kazakhstan, Kyrgyzstan, Tajikistan, and Xinjiang, China.
Family: The apple is a member of the rose family, rosaceae.
Common Names: Apple, Apfel (Germany), Pomme (France)
Related species: Pears, Quince, medlars, hawthorns
Distant affinity: Apricots, plums, cherries, peaches, pears, raspberries, strawberries, almonds, rose apples, etc... the list is very long.
The apple is believed to have originated in the mountains of Central Asia in southern Kazakhstan, Kyrgyzstan, Tajikistan, and Xinjiang, China, and has found its way around the globe starting on the silk road from Asia to Europe. Today, there are over 10,000 varieties of apples in cultivation worldwide. Each locale boasts its own lineup of apple varieties. The apple's incredible climate adaptability has lead to apples growing in the Bahamas all the way to the far Northern reaches of the globe, including Alaska.
The apple is temperate in origin and thrives in climates with mild but chilly Winters and mild to warm Summers. However, due to its amazing ability to adapt to wide range of climates, today there are low chill apple varieties that are well adapted to climates that have little or no chill at all during the Winter. Conversely, there are many apple varieties that have enhanced cold hardiness and bloom very late so that they can withstand the harsh Winters in climates as cold as USDA zone 5 and below.
Chill Requirements: Apples are amongst the latest deciduous trees to defoliate, and need to accumulate most of their chill in late Winter and into the Spring. Most of the commonly published chill ratings are highly inaccurate. In fact, the chill requirements of apples is still poorly understood. The most accurate way to describe chill requirements is to classify apples into low, medium or high chill cultivars. Low chill cultivars include short season "Summer-style" apples like Anna and Dorsett golden. These cultivars will ripen fruit over a period of 3 months in warm climates and can bear up to three crops a year. However, the frequent cropping will deplete the tree and subsequent crops bear smaller and smaller sized apples. There are also long season low chill subtropical cultivars, most of which originate in Australia. These include for example Lady Williams, granny smith, and pink lady. The long season subtropical apples generally require long growing seasons only found in California, Florida and other warm-temperate or subtropical climates around the world.
Lack of chill tends to significantly affect tree vigor. When an apple tree undergoes delayed defoliation as is typically found in California or Florida, the bud beneath each leaf will tend towards becoming a fruiting spur. The result is much earlier flowering and excessive spur production at the expense of adequate vegetative growth. In cold Winter climates, apple trees can take anywhere from 5 to 7 years before they will start to fruit. In contrast, in warmer climates, fruiting starts immediately after planting. This tendency towards excessive bloom is what makes apples very forgiving of lack of chill. Most medium chill varieties will fruit adequately all the way into the warmer coastal climates of Southern California.
There are some varieties that require an excessive amount of chill that can only be met in cold Northern climates. These are cultivars that tend to bloom very late. Most of these high chill cultivars tend to be cider apples from Europe. Most likely, they inherit their high chill requirements from the wild European crab apples. These high chill varieties will struggle to grow and fruit even with medium chill accumulations as high as 800 hours.
Growth Habit: Apples are essentially deciduous trees that can grow upwards of 30 feet or more, but most apple varieties will grow to about 25 feet. Some subtropical apple varieties such as Anna, Dorsett Golden and Granny Smith have almost no chill requirements and will actually remain evergreen in milder climates. The vigor and growth patterns are highly variable amongst different varieties. Some varieties such as Gravenstein, bella de jardin and Nehou are incredibly vigorous and can easily reach heights above 40 feet on seedling rootstock. Some varieties are spreading, others tend more towards vertical growth. Yet others tend toward weeping; the limbertwig varieties are named after their limber weeping growth pattern.
The vigor of apples is controlled by using dwarfing rootstocks. Semi-dwarfing rootstocks such as MM-111 and Budovski 9 lead to trees roughly 15-20 feet in heigh, but will be much smaller in warmer climates. highly dwarfing rootstocks such as M-26 or M-27 will lead to trees as little as 4-6 feet tall. These smaller rootstocks are not drought or heat resistant and will cause the trees to go dormant prematurely during intense heat spells. Thus they are not recommended in warmer climates where the dry season is long, such as California, Australia and the warm Mediterranean climates of Europe.
Flowers: Apple trees bear five petaled, 1-1.5 inch in diameter rose-cented blossoms that emerge in late Winter and early Spring alongside the budding of the leaves. Most cultivars bear flowers that are generally white with a pink tinge that gradually fades. However, a number of red and pink fleshed cultivars bear spectacular flowers that are deep pink without any white color, or stark purple and red fading into white.
Fruits: Apple trees bear fruit on fruiting spurs that typically appear on second year wood, but can also emerge on first year wood. However, spurs are long lived and will continue to bear again and again. Apples have an incredible variation in size, color, flavor and texture. The typical apple will be anywhere from 2-4 inches in diameter. The center of the fruit contains five carpels arranged in a five-point star, each carpel containing one to three seeds. The flesh can vary in color, from light green or pure white to deep red in color, with all shades in between from yellow and orange to pink.
Flavors also vary to a large degree. Most commercial apples seek to provide a very balanced, mild flavored apple. Thus there is little variation in the flavors found in the store. However, heirloom cultivars feature a whole kaleidoscope of flavors: anise, licorice, banana, lychee, "vineous", strawberry, raspberry, cherry, vanilla, herbs, bitters and so on. It is very hard to do justice in words to the plethora of amazing flavors of apples.
In general, apple cultivars fall into one of three classes. Early apples, also known as Summer apples, mid-season, or Fall apples, and late season, or Winter apples. Each one of these classes of apples have very distinct characteristics that govern their flavor and keeping qualities. Summer apples tend to be more tart and often will feature overtone of berry flavors. For example, pink pearl, a pink fleshed Summer apple produces juice with a pronounced strawberry taste. Summer apples generally have a soft-flesh characteristics that causes them to keep poorly and quickly rot once bruised. Most Summer apples keep for only a few weeks in cold storage, after which they quickly turn mealy and loose flavor. Summer apples tend to be the best suited apples for both juice and apple sauce production.
In contrast, Winter apples tend to have very firm flesh and can keep for a very long time. For example, pink lady will keep up to a year in conventional cold storage. Winter apples also feature an incredible fruit flesh hardiness. Unlike Summer apples, when bruised, a Winter apple will actually heal the bruise instead of rotting. A winter apple can also withstand severe frost episodes, and can survive unscathed on the tree through short duration freezes down to 22F without any degradation in quality. In California, it's not unusual for very late Winter apples to continue to improve on the tree even after hard freezes down into the 20's. In contrast, a Summer type apple would turn to mush in any temperatures below 30F.
The third type of apple, the typical Fall apple has a much wider spectrum of attributes. Often Fall apples can be hybrids of both Summer and Winter apples and feature properties of both. However, in general, the later in the Fall and apple ripens, the more its qualities tend towards a Winter apple. The converse is true as well.
Apples will fall into one of three usage categories depending on their texture and flavor: a cooker, a cider, or a dessert apple. A good cooking or processing apple will usually feature enough tartness so that it doesn't become bland once cooked. It will also need to retain its shape after cooking but yet still be tender to the bite. A good cider apple needs to be juicy and will feature either a high sugar content, bitter flavors, or sharp, acid flavors, or all three of the aforementioned properties. Some cider apples have no acidity at all, yet be super sweet. Others are super tart. Yet others are seriously bitter to the point of inedibility, but the bitter compounds are often needed in small doses (typically 10%) to impart body to the cider. Finally, any apple that is good enough for eating out of hand will qualify as a dessert apple, also known as a table apple. Often, an apple will fit into all three categories. For example, gravenstein apples are delicious to eat out of hand, and are highly suitable for both cider and cooking.
Location: Apple trees are not very demanding in their requirements, and will thrive in a wide varieties of soils and climates. However, both soil and climate attributes have a significant influence on flavor. Some cultivars are more demanding than others and require deep continuously moist and loamy soils to flavor to high qualities. Typically, modern commercial cultivars are less dependent on soil and climate and will be more uniform in flavor no matter what the conditions are. But most heirlooms tend to be picky, so make sure to look up a specific cultivar's requirements.
Chill and bloom time is also an important factor to consider. Low chill, early blooming cultivars will not succeed in cold climates because blossoms will freeze. For example, dorsett golden from the Bahamas will bloom at the first Winter warm spell and be frozen out once the weather turns cold again. High chill, late blooming cultivars often do not succeed in warmer districts. For example, Noel des Champs normally blooms in late May but will not leaf out and bloom until August in Central California, leading to a lack of vigor and fruits that do not have time to size up properly and ripen in time for when the tree goes dormant again.warning.pngUnsupported type "_geo" defined for property.
Irrigation: Apple trees require continuously moist soil, otherwise they will go dormant as a result of drought conditions. In warmer and drier climates, vigorous rootstocks with extensive root systems are highly recommended, letting size be determined by Summer pruning. Anything smaller than a semi-dwarf rootstock is not recommended. Drip irrigation along with a good mulch cover will not only keep the soil cool but it will also keep water off the tree and reduce the incidence of disease.
Fertilization: apples are not demanding when it comes to fertilizer. Often a straight nitrogen fertilizer is all that is required. However, flavor will be much improved with a wide spectrum fertilizer rich in micro-nutrients. This is most easily achieved with the application of organic matter. For best flavor, it is also recommended to withhold fertilizer for at least 6 weeks prior to harvest, as excessive nitrogen fertilizer tends to make apples taste bland.
Pruning: Apples can be pruned into a wide variety of shapes, including espalier, open center and central leader. The best shape is usually a function of the cultivar. Cultivars that tend towards a broad growth pattern will do better with a central leader to promote more vertical growth. In contrast, a cultivar with strong vertical growth tendencies will do better with an open center.
Another factor to take into account is if a tree is a tip bearer or a spur bearer. Pruning all the tips on a tip bearer can be a sure recipe for poor cropping.
The best time to prune is late Winter to early Spring. However, if size restriction is desired, then it's best to prune late in the Summer. Winter pruning tends to induce much more growth than Summer pruning.
Frost Protection:: In lower latitudes, apples need no frost protection at all. However, when growing apples in USDA zone 5 and colder, it is necessary to select hardy, late blooming cultivars that can withstand the longer, colder Winters. Some frost protection may be necessary during extreme cold spells.
Pollination: Most apple cultivars require a distinct genetic cultivar for cross-pollination. However, there are a few exceptions where some varieties are self fertile. The challenge is to match varieties that have bloom times that overlap.
Propagation: apples are usually propagated by grafting onto select rootstocks. Seedlings rarely produce anything that even closely resembles the parent. That is because the apple is an example of "extreme heterozygotes", which means that genetically, the offsprings are completely different from the parent. There are exceptions to this rule, most notably "snow" and "antonovka", which produce offsprings very similar to the parent.
However, the extreme genetic variation is the very reason that often, random or chance seedlings produce new varieties of interest. In fact, at least 90% if not more of the varieties in cultivation today originated as chance seedlings, not as deliberate crosses. The claim that apple seedlings revert to crab apples has nothing to do with genetic reversal of improved genes, but has more to so with the fact that in the old days, crab apples were often used as pollinators in commercial orchards. In a normal backyard orchard, seedlings often produce interesting and unusual new varieties worth keeping. Only if a combination of superior traits is desired for commercial purposes does it it necessary to plant thousands of seedlings to select a few superior strains. While chance seedlings usually provide interesting flavors and appearance, it is rare to see combinations of superior disease resistance, precocity and reliable flavor and quality not easily influenced by weather and soil.
The three main classes of apple rootstocks in use today include the malling series (MM), the Geneva series (G) and the Budagovsky series (B). Out of these three, the malling series continue to be the most popular rootstocks, with MM-111 being the choice rootstock for warmer climates due to it's adaptability to drought and extreme heat.
Pest And Diseases: Apple trees have a rather large number of pests. The most common pest which is most visible in home orchard is coddling moth, which leads to the well known problem of ending up with wormy apples. However, there are a number of other bugs that love apples, including apple maggot and plum curculio. The most common fungal disease is apple scab, which is prevalent in areas of high rainfall.
Harvest: There are enough apple varieties to supply a fresh harvest from late May all the way into mid February in the milder parts of California. However, the peak harvest period is mid August to mid October, which is when the majority of the varieties ripen. Summer apples need to be picked off the tree due to their susceptibility to bruising, but many late Winter apples can drop to the ground and remain delicious.
Storage And Consumption: In general, apples are incredibly versatile. Many varieties store and ship very well. Much like fine wines, some of the older heirloom apple varieties need to remain in cold storage for some period of time before they reach their peak flavor. New storage techniques can prolong storage for many months, even up to a year or more.
Commercial Potential: Apples are already the largest fruit crop in the world, but there are new commercial opportunities within the realm of the exotic. In Northern latitudes, heirloom and heritage apples are making a comeback and command top dollars on the market. Restaurants are interested in particular in antique and unusual varieties to add to their menus.
In the tropics, there is also an opportunity to introduce apples in wider cultivation. Apples in the tropics also command top dollars. There are ongoing efforts to grow apples commercially in the tropical regions of the world, including Africa and Southeast Asia.
Apples varieties are classified under the Apple Varieties node. (If this link is red, it means the category has not been added yet.) Click on the variety category link to navigate to the varieties.
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