Apricot trees (\(Prunus\) \(armeniaca\)) are temperate fruit trees known for their early spring blossoms and sweet, golden fruit. For fruit production, pollination must successfully occur, transferring pollen to the female parts of the flower, leading to fertilization. Gardeners often wonder if these trees require a partner or if they are capable of self-pollination. This article explores apricot pollination and provides insight into maximizing fruit yield.
How Apricot Trees Handle Pollination
The majority of apricot cultivars grown today, especially commercial varieties, are classified as self-fertile. Self-fertility means the tree can produce viable fruit using pollen from its own flowers. This simplifies planting, as a single tree can set a full crop without another distinct variety nearby.
The biological mechanism involves transferring pollen grains from the anther (male part) to the stigma (female part). This transfer can occur within the same flower or between different flowers on the same tree. Once the ovule is fertilized, the tree begins developing the ovary into the fleshy fruit.
While the tree’s genetics permit self-pollination, external agents are required to physically move the pollen. Insects, especially honeybees (\(Apis\) \(mellifera\)), are the primary vectors for transferring the sticky apricot pollen. Even on a self-fertile tree, bee movement significantly increases the probability of successful contact, leading to higher fruit set percentages. Most modern apricot breeding programs prioritize self-compatibility to ensure reliable yields for both home and commercial growers.
Factors Affecting Fruit Production
Although most apricots are self-fertile, certain heirloom or less common cultivars exhibit self-incompatibility. These varieties require a different compatible cultivar for cross-pollination because their genetic mechanisms prevent their own pollen from successfully fertilizing the ovule.
Temperature and Frost Damage
One significant external constraint is temperature, especially late spring frosts. Apricot trees bloom early, making their blossoms highly susceptible to damage. Temperatures below 28°F (-2°C) can kill flower buds, open blossoms, or newly fertilized fruitlets. This susceptibility to cold is the most common reason for crop failure.
Weather and Pollinator Activity
Poor weather during bloom also limits fruit production. Cold, rainy, or windy days drastically reduce the activity of pollinating insects. Even if flowers are self-fertile, insufficient pollen movement results in a poor fruit set because the pollen never reaches the stigma.
Chilling Requirements
Apricot trees require specific chilling hours during winter dormancy for proper bud development. If the tree does not receive enough time below 45°F (7°C), the flower buds may not open uniformly or may open weakly. This physiological requirement must be met to produce viable blossoms ready for pollination.
Strategies for Successful Yield
Even when an apricot variety is self-fertile, fruit set and yield are substantially improved by cross-pollination. Introducing pollen from a genetically distinct and compatible cultivar leads to a higher percentage of flowers developing into fruit. This phenomenon, known as xenogamy, results in a more reliable and heavier crop compared to relying solely on self-pollination.
Encouraging Cross-Pollination
Growers can implement this strategy by planting a second, different apricot tree within proximity (usually within 100 feet) to allow for adequate bee travel. Alternatively, a compatible scion (a piece of shoot) from a different variety can be grafted onto a limb of the existing tree. Grafting ensures a pollen source without requiring space for a second full-sized tree.
Assisted Pollination
When natural insect activity is low due to unseasonable weather, growers may employ assisted pollination techniques. This involves manually transferring pollen from the anther to the stigma using a small, soft brush or a cotton swab. This intervention ensures the necessary pollen transfer is physically accomplished, maximizing fertilization chances even on calm or cold days.