Many factors can contribute to the success of an apple tree. Selecting the right variety for your climate, planting at the proper time and location and understanding pollination are all important.
The more than 7,500 cultivars of apple trees are bred for different taste, size, texture and other qualities. They are produced by either grafting or from seeds.
Pollination
Most apple varieties are self-sterile and require pollination from another variety in order to produce fruit. This is usually done by bees or wasps who transfer pollen from the male stigma to the female ovary. However, effective pollination requires synchronization of flowering periods between the pollinator and the fruiting variety. In addition, the blooms must be open and receptive to pollen in order for successful cross-pollination.
This is a complex issue for growers, and one that can affect both the quality of the fruit and the total crop yield. Fortunately, there are many things growers can do to improve pollination and increase the probability of success. Regular monitoring of flowering patterns, creating a habitat that attracts pollinators and careful variety selection can all lead to a successful harvest.
The bloom period of different apple varieties must match in order for successful pollination. In general, early or mid-season varieties (e.g. Zestar, Golden Delicious) can be pollinators for varieties with similar bloom times. However, later season varieties such as Cox, ‘Enterprise’ and ‘Golden Delicious’ require late season flowering apple varieties to pollinate them.
Apple varieties that are grafted on rootstocks with differing bloom periods also require synchronization of their flowering. This is because the rootstock can induce a delay in the onset of bloom in the top-grafted variety, thereby altering the effective pollination window.
Some varieties are also genetically incompatible with their close relatives. Consequently, it is necessary to choose pollination partners that are not related for successful fruit set. This is especially important for triploid varieties, which often have excellent disease resistance but require two other apple trees in order to produce fertile offspring.
The flowers of most apple varieties have five stigmas surrounded by anthers, with the ovules on the inner part of the flower. The ovules are covered by five carpels, each containing two to four seeds. During the fruiting phase, the seeds develop in the ovary and are shed shortly afterward. Therefore, the ovules are very sensitive to fertilization and will fail to develop if not properly pollinated. In addition, the ovules can be misshapen if only one side is pollinated.
Fruits
A mature apple tree produces a high quantity of fruit. Depending on the cultivar, this may be for eating, cooking or dual-purpose use. An apple tree will need another tree of a different variety that blossoms at the same time to pollinate it and ensure a successful crop. Alternatively, it is possible to plant self-fertile apple trees that will produce a good crop without the need for pollination.
The quality of an apple is influenced by many factors, including the amount of water and sunlight that it receives. An apple’s color, texture and taste are all determined by its genetic makeup and environmental conditions.
As the weather warms up in spring, an apple tree begins to flower. When the flowers are pollinated by bees, the fruits start to develop. In ideal conditions, wind and bees can spread pollen from apple to apple to ensure a high crop. However, if the weather is wet or rainy during this period, pollen may be washed away and the apple crop will suffer.
In an orchard, the number of apples produced each year will depend on the variety, weather conditions and the way in which the apple tree is managed. The goal of any grower is a high-yielding, consistent quality crop that satisfies the end user. This can be achieved through various management practices, such as pruning the apple trees to encourage air circulation and thinning the developing fruits.
One of the most important factors influencing the quality of an apple is its ability to scavenge free radicals. The more antioxidant compounds an apple has, the more it will protect against oxidative stress caused by a number of different stresses such as heat and chemicals. The amount of these compounds in an apple is related to its canopy position, with the fruit on the top and west side of the tree tending to have higher levels of antioxidants than those on the east and south sides of the tree.
The nutrient content of the apple also depends on its canopy position. Leaves and fruit in the outer canopy intercept more sunlight, resulting in more photoassimilates being transported into the apple. This results in the apple having higher mineral content, which is reflected in the internal quality of the fruit.
Soil
The health and success of an apple tree depends on the condition of the soil. Trees are most productive in well-drained, fertile soil rich in organic matter. However, they will grow and produce fruit in a wide range of soil conditions. It is important to choose a site that receives at least six hours of direct summer sunlight. The soil should be light to medium textured, because heavy clay soils limit root growth. It is also essential that the soil be able to retain moisture but not become soggy.
The pH of the soil should be slightly acidic to neutral. High pH values result in nutrient tie-up or toxicity, which will restrict fruit production. Ideally, the soil should be amended with lime before planting to achieve this. The soil should be deep enough to allow for adequate root development and the presence of microorganisms.
After planting, the soil should be lightly raked to eliminate any air pockets and packed down to encourage proper rooting. During the first year, water the soil at least twice weekly. It is important that the soil does not remain soggy, which can lead to fungal diseases. Avoid planting trees in low areas, where cold air tends to settle and may cause root rot.
A good practice is to mulch with wood chips. This will help conserve moisture, keep weeds at bay and add nutrients to the soil. A good time to apply these is early spring before the new leaf buds begin forming. A regular nutrient program will promote a healthy tree and more abundant harvests.
Because a variety of factors affect the nutrient availability to plants, routine soil and tissue sampling should be part of the overall management plan for any orchard. These samples can be used to track the levels of nitrogen, phosphorus, potassium, calcium and magnesium in the soil and plant tissues. The results can also be useful in developing a fertilization schedule. This is particularly important because the nutrient requirements of the plant will vary as it matures. The optimum planting density for apple trees will vary by cultivar and rootstock, but generally is in the range of 400-2,500 apple trees per acre.
Care
Apple trees can be affected by a wide range of diseases and problems, from minor to severe. The key to fighting off disease problems is preventative maintenance. Maintaining proper soil conditions, adequate water levels and fertilization can help keep your apple tree healthy. In addition, some diseases can be prevented by choosing trees that are resistant to the disease or by spraying your apple tree with an organic anti-fungal or insecticide.
When growing an apple tree, it is essential to plant the correct variety for your climate zone and location. If you choose the right type of apple for your situation you will need to provide a little extra care during the first couple of years but once established your tree will need remarkably little after that. A few basic tasks like providing a mulch around the tree, pruning correctly and thinning fruit will help your apple trees produce large crops each year.
After planting, an apple tree needs to be kept well watered throughout the growing season. A foliar spray with an organic pesticide can be helpful in preventing diseases such as apple scab and cedar-apple rust.
During the first years of growth, an apple tree will need to be pruned to shape it. A properly trained tree can become a beautiful garden focal point.
In the early summer, an apple tree will need to be thinned. After a heavy bloom and good fruit set, an apple tree will often have more apples than it can handle. To improve the size and quality of the remaining apples, thin the fruit by removing some of the young fruits. This will also help to prevent biennial bearing.
A mulch of wood chips or leaf litter around an apple tree can help suppress weeds, conserve moisture and add organic matter to the soil. If using a mulch, it is important to water the tree through its roots rather than just the top of the root system to avoid overwatering and fungal issues. A layer of mulch also helps to reduce the need for watering by insulating the ground temperature and helping to regulate soil moisture. A good general purpose fertilizer, such as blood, fish and bone, should be applied in early to mid spring and again in late autumn.
