The apple is a hardy, deciduous woody perennial tree that grows in all temperate zones. Apples grow best where there is cold in winter, moderate summer temperatures, and medium to high humidity. Apples can grow from 10 to 30 feet tall and nearly as wide. Apples are moderately fast growing, but growth slows with age. Apple trees can live for 100 years or more. Apple trees bloom in the spring, set fruit, and take from 100 to 200 days to reach harvest depending upon the variety.
Yield. An apple tree can yield from 75 to more than 130 pounds of fruit each year.
Apple varieties. There are nearly 10,000 different kinds or varieties of apples. About 7,000 varieties or cultivars grow in North America. Only about 1,000 of these of these are grown commercially or in home gardens.
Some apple varieties are “sports” or accidental mutations of another variety and others are bred–created by apple breeders through cross selection. Not every sport is productive and worthy of growing.
Apple tree sizes and rootstock. An apple tree can be a standard or full-sized tree which grows to 30 feet tall and can take 6 years to bear its first fruit or a dwarf or semi-dwarf trees which can grow from 6 to 20 feet tall. Most dwarf and semi-dwarf trees are grafted on a rootstock which keeps them small. Dwarf and semi-dwarf trees produce full-sized apples in about three years.
A grafted apple tree has a root system that is different from the fruit-producing portion. Some apple trees have more than one graft; some varieties have not only a different root system but also a different trunk and branches.
Dwarf, semi-dwarf apples. Apples are dwarfed as a result of the type of root system onto which they are grafted. Many apple varieties can be purchased as either standards or dwarfs or semi-dwarfs depending upon the rootstock. Root systems are identified by their growth at maturity and planting needs. Here are some, but not all, examples:
• ‘Seedling’: this is full-growth tree with strong roots.
• ‘M.27’: this tree makes 15 percent of full growth and is good for containers.
• ‘ M.9’: this tree makes 25 to 35 percent full growth; plant in moist, well-drained soil.
• ‘M.26’: this tree makes 30 to 40 percent full growth; plant in well-drained, dry soil.
• ‘MARK’: this tree makes 30 to 40 percent full growth and is very cold hardy and resistant to fireblight.
• ‘M-7’: this tree makes 40 to 60 percent full growth and can be grown in wet soil.
• ‘MM.106’: this tree makes 45 to 65 percent full growth; it can be planted in wet soil but may be susceptible to root rot.
• ‘MM.111’: this tree reaches 65 to 85 percent full size, tolerates a wide range of soil and is drought resistant and fireblight resistant.
Many apple dwarfing rootstocks were originated in England at the Malling Research Station; this accounts for the Ms in their names.
Spur-type and branching apple trees. Apples can be divided into spur-type or branch-fruiting type trees. Spur-type trees bear fruit on short twigs called spurs. Other trees bear fruit along branches. Spurs tend to grow close together and so spur-type cultivars bear more fruit than the branching or non-spur trees. Spur varieties tend to bear fruit earlier in life than branching varieties. Individual spurs may bear fruit for ten years or more. Standard non-spur trees bear on twigs that tend to be short lived.
Chilling requirements. Apples have chilling requirements or chilling hour requirements. This is the number of hours at 45°F (7°C) or less that the cultivar or variety requires each winter in order to flower and leaf out the next season. Chilling hours can vary from 1,000 or more to as few as 400 hours. It is important to choose an apple variety suited to your climate and winter temperatures.
Site and climate. Apples grow best in full sun away from constant wind. An apple tree that fall in partial sunlight is not likely to fully yield. Apples grow in Zones 3 to 9. They can tolerate winter temperatures as low as -40°F. Apples generally do not grow well close to the ocean where temperatures remain moderate most of the year. Late spring frosts can kill apple flowers (they bloom in late spring after peaches, cherries, and almonds), and early fall frosts can damage fruit. Choose a variety suited to your growing region.
Apples grow best in well-drained loamy soil, although they will grow in more sandy soil or in soil with some clay. They grow best in a neutral soil pH of 6.0-7.0.
Pollination. Most apple varieties have flowers that contain male and female parts and so are self-pollinating. These trees will set fruit without cross pollination. However, many varieties are self-infertile and require a pollenizer. Even trees that are self-pollinating may have a better fruit-set if there is cross pollination. Apples can be pollinated by bees and insects or by pollen that floats on the wind. Plant your apple tree within 40 to 50 feet of another apple tree that blooms at the same time or graft a branch from a suitable pollinator onto your tree. Flowers that are only partially pollinated will tend to bear fruit that prematurely drops.
Planting and spacing. Apple trees can be purchased either bareroot, balled-and-burlapped, or in a container. Bareroot trees are available in the winter and early spring when the trees are dormant and without leaves. Plant bareroot trees in spring as soon as the soil can be worked and before the trees begins to significantly leaf out. These trees are commonly grafted and without branches, and so are called whips. Make the planting hole large enough that the roots can be spread out fully. Look for the soil line on the tree and plant the tree at that level or an inch or two deeper. If the tree is grafted, set it in the hole so that the graft is visible when planted.
A balled-and-burlapped tree is a tree whose roots are in soil; the roots are enclosed in burlap. Balled-and-burlapped trees are commonly available in spring also; however they may be found later in the year. Plant a ball-and-burlapped tree by positioning the tree in the planting hole at the same depth that it was growing at the nursery. After positioning the ball into the hole, remove all twine or rope used to hold the burlap and ball together. Then open the top of the burlap so that water can penetrate the soil ball. Slide the burlap out from under the fall and lightly tamp in soil around the root ball.
A container grown tree can be planted any time during the growing season. Remove the container carefully and plant the root ball at the same depth as in the container.
Space apple trees so that they have full room to mature. Consider the variety of tree when placing the tree in the garden, yard, or orchard. A standard tree will require 20 to 30 feet of growing space; a semi-dwarf will require 15 to 20 feet and a dwarf tree will require 10 to 15 feet. For a small garden, choose a dwarf tree or a tree trained as an espalier or column or small bush.
After planting, water each tree in thoroughly and fertilize with high-phosphorus liquid starter fertilizer.
Water and feeding. Newly planted apple trees require moderate watering weekly. Set the water on low and allow it to seep into the soil allowing; roots will follow deep watering and become well established. Established apple tree require only infrequent watering but be sure to water all trees during prolonged dry periods.
Apple trees will grow 8 to 12 inches each year. Feed apples with a mulch of aged compost applied liberally around the base of the tree once or twice a year, in spring or in late fall after leaves have dropped. A half pound of evenly-balanced 10-10-10 fertilizer for each year the tree has been alive to a maximum of 10 pounds per tree per year can be applied. Low levels of potassium, calcium, or boron can reduce growth and fruit quality. Test the soil for its nutrient content. Spread gypsum on the soil to raise the calcium level.
Yields can be improved with a foliar feeding of seaweed extract when buds begin to show color, again after petals fall, and once again when fruits are less than 1 inch in diameter.
Care of young trees. Allow apple trees to become well-established before fruiting. During the first two years, handpick off flowers and young fruit not allowing them to develop; this will give the tree increased energy to establish its roots. In the third year, allow the tree to bear a small crop. Do not allow a limb to become so burdened with fruit that it will bend or break.
Thinning. Thinning fruit will ensure the quality and size of the crop. Thinning will also reduce the tendency of some apple varieties to alternate-bear that is bear fruit every other year.
A few weeks after fruit sets, some fruit on the tree will naturally drop off. This is called June drop; it is nature’s way of thinning the crop. Apple trees produce more blossoms and fruit than is necessary for a full crop.
Additional thinning will benefit the tree. The rule of thinning fruit is to allow plenty of room for fruit to develop. Look for clusters of fruit and remove smaller apples in each cluster before the fruit reaches 1 inch in diameter. On larger trees, you can leave two fruits on each spur and on dwarf trees leave one fruit on each spur. One method is to remove all the fruit on every other spur. It is probably best to break up all clusters leaving just a single fruit. Fruit that touches another fruit can be susceptible to disease or pest attack.
Pruning. Apple trees, like most trees, benefit from pruning. Pruning will allow the apple tree to produce quality crop. If you start early in the tree’s life, you can prune to a central leader; a central leader is a branch that is allowed to grow vertically and form a main stem from which all the fruiting branches will grow at regular intervals. Apple trees tend to be naturally vase shaped having no central leader but several scaffold branches.
Prune an apple tree so that plenty of light and air can penetrate into the center of the tree. One guideline is to prune so that a bird can fly directly through the tree without touching its feathers on a branch. That means pruning out dense, crossed branches.
Follow these steps to prune an apple tree:
- Remove all diseased, dead, or broken branches.
- Remove all watersprouts. Watersprouts are fast-growing vertical branches that usually have no side branches.
- Remove all suckers. Suckers are the fast-growing shoots that grow out of the soil from the roots below the soil surface.
- Remove tight V-branching crotches. These are narrow crotches formed by branches that will not support the weight of a full crop of fruit.
- Remove crossing or rubbing branches. If two branches cross and rub against each other they can cause a wound that may allow insects or fungal disease to attack the tree. Remove the least desirable branch.
- Never prune away more than one-third of the total tree in a single growing season.
- Always prune to a growth bud or flush to a main branch or trunk. Remember that apple trees produce on same lateral spurs several years in a row.
- Prune every year. Once a tree has been well pruned, it will need less annual pruning; only the removal of crossing branches and twiggy growth.
- Prune in late winter when the tree is dormant and before buds appear, particularly heave pruning. A light maintenance pruning can be done in summer working around the fruit set.
Pests. Apples are susceptible to a number of insects that are very difficult to control without preventative spraying. Among the pests that attack apples are scale, apple maggots, codling moths, fruitworms, leafhoppers, and mites. Many pests can be controlled with pheromone-bated insect traps and spraying.
- Here is a general spraying schedule:
- Apply a dormant oil spray before buds open and when the temperature has been above 33°F for 48 hours.
- Apply a multipurpose fruit tree spray when the buds begin to break.
- Do not spray when the tree is in bloom.
- When nearly all the flower petals have fallen begin applying a multipurpose fruit tree spray every 10 to 14 days.
- Discontinue all spraying two weeks before harvest.
Diseases. Apple trees are susceptible to many fungal diseases that are difficult to control without use of preventive spraying. Cedar-apple rust cause yellow-orange spots on leaves and fruit. Powdery mildew results in a dusty white coating on leaves and fruit. Apple scab results in greenish brown lead and fruit spots. Fireblight is marked by blossoms that appear watersoaked and twigs that look black and scorched.
The best preventative approach to apple diseases is to choose varieties that are resistant to the diseases in your region. Apart from disease-resistant cultivars, prune trees regularly to allow for ample sun and air penetration into the crown of the tree and prune out any diseased branches, leaves, or fruit. Keep the garden or orchard clean of dead leaves and branches and plant debris. For some fungal diseases, spray early in the season with sulfur or copper every week until symptoms disappear. Do not spray with copper more than twice during the summer or the following year’s crop may be inhibited.
For home gardeners, many pests and diseases may not interfere with a harvest. The fruit appearance may be affected, but the quality may remain.
Harvest. Apples come to harvest from midsummer through late fall. The best way to know if apples are ready for harvest is to taste them; select one and try it. Also consider skin color and fruit drop. Apples are usually ready for harvest when they reach full color; full color may vary according to the variety. A mature apple will come away from the tree easily; lift the apple up and twist in a rotating motion. It should not be necessary to cut an apple from the stem. Late ripening apples usually come to harvest more quickly than long-maturing early and mid-season varieties.
Varieties. There are many apple varieties to choose from. Consider first your region and the number of chilling hours. Next consider the space you have to grow an apple tree. Then consider how you plan to use the fruit and when you want the fruit to come to harvest, early, mid-season or late.
Storing and preserving. Apples will keep for 6 to 8 weeks in a cool place; a refrigerator just above 32°F is best. Late-maturing apples are better keepers than summer apples. Commercial growers often place apples in cold storage fro 6 to 12 months. Apples kept in storage should not be diseased or damaged or other fruit may be affected. Apples are often wrapped individually in paper to avoid spoilage.
Common name. Apple
Botanical name. Malus pumila
Origin. Southwestern Asia