Apple Tree Propagation and Pollination

Apple Tree Propagation

Apple tree propagation is essential for the production of consistent and high-quality fruit. The most widely used techniques for apple propagation in commercial orchards include grafting, budding, and cuttings, with grafting being the dominant method due to its ability to maintain the genetic traits of the desired apple variety.

Seed Propagation: Not Suitable for Commercial Apple Cultivation

Although apple trees can be grown from seeds, this method is rarely used in commercial apple farming. According to NDSU, seed propagation results in trees that vary genetically from the parent, leading to inconsistent fruit quality and characteristics. Apple seeds are genetically diverse, meaning the resulting trees often produce inferior or entirely different fruit from the parent tree​. This means that if we plant the seeds from 10 apples of exactly the same variety, all 10 apple trees that will be created will be significantly different and give accordingly different fruits. Thus, commercial growers avoid seed propagation in favor of methods like grafting that ensure uniformity and predictability. Consequently, professional farmers choose grafted seedlings to achieve product uniformity and quality.

Grafting: The Most Common Way to Propagate Apple Trees

Grafting is the most reliable propagation method in commercial apple orchards, especially whip and tongue grafting. According to North Dakota State University (NDSU), the process involves selecting a scion, which is a shoot from a mature apple tree (parent or mother plant) of the desired variety, and attaching it to a rootstock that will support the tree's growth (responsible mainly for the root-system and part of the trunk). The rootstock determines the tree's size, adaptability to different soil conditions, and disease resistance. Most apple trees are grafted or budded onto wild crab apple seedlings. Seedling rootstocks derived from diploid cultivars such as Golden Delicious, Yellow Newton, Wealthy, Macintosh, and Granny Smith are also commonly used. Dwarfing rootstocks like M9, M4, M7, and M106 are preferred for high-density planting systems, as they help control tree size and promote earlier fruit production.

Grafting advantages include ensuring that the apple tree will produce fruit identical to the parent tree. It also allows growers to control tree size through dwarfing rootstocks like M.9 and M.26, which are widely used in modern commercial orchards for their ability to produce more compact trees with earlier fruit-bearing capabilities.

Budding Techniques: T-Budding and Chip Budding

T-budding and chip budding are common techniques used in nurseries, particularly for producing large numbers of trees in a relatively short time. T-budding involves inserting a bud from the desired variety into a T-shaped cut in the rootstock's bark. On the other hand, chip budding involves attaching a chip of bark and wood with a bud from the desired variety onto the rootstock. These methods, while labor-intensive, are effective for ensuring genetic consistency and high success rates in tree establishment.

These budding methods are typically used during the growing season when the bark is easier to manipulate. While they are mostly employed in nurseries for mass production, they can also be used in smaller-scale propagation efforts.

Layering and Cuttings: Lesser-Used Methods

While layering and cuttings are valid propagation methods, they are less common in commercial settings due to their slower and less reliable nature. Layering involves burying a branch from the parent tree to stimulate root growth while still attached, whereas cuttings require treating a severed branch with rooting hormones like indolebutyric acid (IBA) to encourage root development. 

Apple tree pollination

Pollination is a critical factor in apple tree production, and ensuring proper cross-pollination through a combination of suitable tree varieties and bee management significantly enhances yield. Apple trees, which are mostly self-incompatible, require cross-pollination for fruiting, making the use of compatible pollenizer trees and effective bee activity vital.

Cross-Pollination and Compatible Varieties-Pollinizers

Most apple tree varieties are not self-fertile. This means that most apple trees need pollination partner trees of different varieties to set fruit. Even the self-fertile apple varieties are reported to produce higher yields when a pollination partner tree is planted nearby. The various commercial apple cultivars flower at different times, starting with Granny Smith and ending with Red Delicious. Apple growers must plant pollinating cultivars that are compatible and flower at closely the same time as the commercial cultivars. It is also important to place the pollinating cultivars at different spots of the orchard to ensure adequate cross-pollination.

Cross-pollination occurs when pollen from one apple tree is transferred to the flower of another genetically different apple variety. For example, Golden Delicious is an excellent pollenizer commonly planted to aid in pollinating other varieties. However, triploid varieties like ‘Jonagold' and ‘Mutsu’ are unsuitable pollenizers, as they do not produce viable pollen.

Crabapple trees can be particularly useful in commercial orchards as they bloom over an extended period and are excellent pollen sources. This ensures that enough viable pollen is available when the main apple varieties bloom, crucial for consistent fruit production​.

Pollenizer Tree Distribution - Tree Spacing and Orchard Layout

Properly distributing pollenizer trees is essential for ensuring bees can transfer pollen efficiently. Many growers choose to plant one compatible pollenizer for every six to eight fruit-bearing trees. This ratio maximizes cross-pollination while conserving space in the orchard. Other sources suggest a range of one pollenizer per eight to twelve trees, depending on the orchard's design, or alternate rows of primary apple varieties with rows of pollenizers to ensure uniform pollen distribution. Close proximity between trees is important, as honeybees generally forage within short distances, and maintaining a compact but well-ventilated orchard layout improves pollination efficiency. 

Honeybees are the primary pollinators for apple trees. Managing bee populations within an orchard is key to effective pollination. For best results, growers are advised to place 3 beehives per hectare (1-2 two hives per acre). Honeybee hives should be distributed evenly within the orchard to ensure coverage across all apple trees. In addition to honeybees, native pollinators such as bumblebees can also aid in pollination. Bumblebees, which are more resilient in cooler temperatures and stronger winds, can complement honeybee activity during periods of unfavorable weather.

Weather conditions can significantly affect pollination success. Bees are most active in clear weather and when temperatures are above 13°C (55°F). Cold, rainy, or windy weather can reduce bee foraging activity, which may lead to poor fruit set. The growers should minimize or completely avoid using pesticides during the blooming period to prevent harming bee populations and, as a result, the pollination of the apple trees.​

Best Practices for Pollination in Apple Orchards

• Variety Selection: You can plant compatible pollenizer varieties, avoiding triploids, and ensure bloom times overlap between the main crop and pollenizer trees.
• Tree Spacing: To balance growth space and ease of bee movement, you can plant trees 3-6 m or 10-20 feet apart.
• Bee Management: You can maintain one to two hives per acre and distribute them evenly across the orchard.
• Environmental Care: You can protect bees by limiting pesticide use during bloom and introducing flowering plants to attract pollinators.

To read more about apple tree cultivation, read the relevant articles below.

Apple Plant Information and Most Popular Varieties

Growing an Apple Tree from Seed

Growing Apple Trees in Pots

Apple Tree Propagation and Pollination

Site Selection for Apple Trees: Soil and Environmental Requirements

Planting Apple Trees

Watering Needs of Apples: How to Irrigate Apple Trees

Nutrient Needs and Fertilization of Apple Trees

Training and Pruning of Apple Trees

Apple Tree Harvest & Yields

Major Pests and Diseases in Apple Trees: Identification, Symptoms, and Management

How to cultivate apples commercially

Q&As Apple Tree

References

• https://www.researchgate.net/
• https://www.permaculturenews.org/2018/07/07/different-methods-propagating-fruit-trees-cuttings-etc/, https://apples.extension.org/apple-tree-propagation/, 
• https://nhb.gov.in/pdf/fruits/apple/app011.pdf, 
• https://www.permaculture.co.uk/articles/beginners-guide-to-propagating-fruit/, 
• https://extension.psu.edu/orchard-pollination-pollinizers-pollinators-and-weather
• https://treefruit.wsu.edu/orchard-management/pollination/
• https://www.canr.msu.edu/apples/horticulture/pollination#:~:text=Apples%20require%20cross%2Dpollination%20%2D%2D,apple%20orchard%20for%20this%20purpose.