Even though trees are considered asexual, pollination is one of the ways they reproduce sexually with a bit of help from their animal friends.
The process of transferring pollen grains from the male part of a flower to the female part of a flower is known as pollination. This is a critical process, as the survival and evolution of trees depend on successful pollination. While certain trees need to be pollinated by pollen from one flower to another flower on the same tree, others may need the pollen from an entirely different variety of trees transferred to its flowers. Here’s everything you need to know about self-pollinating trees and cross-pollinating trees.
Self-Pollination – What Does It Involve?
Self-pollinating trees only require their own pollen to reproduce, and they can be planted on a standalone basis.
As the name suggests, such trees do not require any pollen vectors. Common examples of self-pollinating fruit trees include sour cherries, apricots, raspberries, blackberries, and peaches. These trees are perfect if you plan to create a small orchard full of fruiting trees in your backyard.
There are two ways in which self-pollination takes place:
- Autogamy: This is a type of self-pollination where an intersexual flower is pollinated by its own pollen. It can only happen when the anther and stigma, the reproductive parts of a flower, are held closely together, and the stigma receives the pollen as soon as it is released.
- Homogamy: This is a type of self-pollination involving bisexual flowers. In such flowers, the anthers bearing pollen and the stigma ripen at the same time in anticipation of pollination.
There are several advantages of planting self-pollinating trees. Firstly, as they aren’t dependent on any pollinating agents, pollination can occur even when the environment may not be otherwise suitable. It also helps to preserve the stable traits within the species.
There is also less wastage of pollen, as the grains are deposited directly from one flower to the other. Moreover, since there are no external carriers involved, there are no changes in features or characteristics of the species. Lastly, trees that self-pollinate don’t need to have colorful flowers or flowers emanating any scent in order to attract pollinators.
However, self-pollination can also impact the health of the species. For example, genetic defects may be passed on. In fact, sometimes flowers that could otherwise self-pollinate develop an internal mechanism to avoid it.
Cross-Pollination – What Does It Involve?
Cross-pollinating trees require gametes from different varieties within a species to keep reproducing. It’s usually carried out by pollinators such as bees, birds, and wind, though it is possible to replicate their function manually with the help of a painting brush. Just like self-pollination, not all trees need or want cross-pollination. Cross-pollination is essential for trees such as apples, pears, and Japanese plums. In some cases, trees that are distantly related and do not belong to the same species can also cross-pollinate. This is referred to as hybridization.
The biggest advantage of cross-pollination is that it aids in the development of offspring with desired traits. They are also healthier when compared to self-pollinated trees, and the seeds produced are much more viable. Moreover, it is indispensable in case you are breeding to find new varieties. In most cases, propagated cuttings may not result in stable mutations as easily as cross-pollination does.
But there are disadvantages associated with cross-pollination too. It may result in the wastage of pollen grains, as they need to be produced in abundance to maximize the chances of pollination. Cross-pollination also requires the presence of suitable pollinating agents, and this is difficult to control. Cross-pollination may impact the quality of harvest—sometimes the fruits could grow smaller than expected and branches may break off unexpectedly.
Over-pollination can sometimes take a toll on the trees too. The added pressure to bear too many fruits during a year can lead to their early death. Trees such as pear, citrus, and apple varieties are extremely prone to over-pollination, and sufficient caution should be exercised when planting these trees. Lastly, even after planting such trees and taking appropriate care, you may have to wait for three or four years to witness the maximum results from cross-pollination.
Cross-pollinating trees face increased risk, as the population of pollinating agents, such as wild bees, flies, wasps, moths, and butterflies, are constantly declining due to changing environmental conditions. If you are planning to have such trees in your yard, make sure to plant pollinator-attractive flowers and ornamental grasses to attract pollinators. Also, cut down on the use of pesticides and use them only when unavoidable.
Which Type of Tree Should You Plant in Your Oregon Yard?
As you may have noted, both cross-pollinating and self-pollinating trees have their share of advantages and shortcomings.
Ideal trees for your yard largely depend on the soil condition. Moreover, if you are keen to have cross-pollinating trees, you’ll need to plant trees that bloom around the same time and can withstand similar conditions, such as weather and the hardiness of soil. You’ll also need to plant trees at the correct distance so that pollination is not a challenge. Plant them close enough so that the pollinators can deposit the pollen grains easily. You’ll also need to select trees that are ideal for pollination and that flourish when cross-pollinated. For best results, your yard should be free of hedges or other obstacles that may make it difficult for pollinating agents to carry out the process.
If you are having a hard time deciding which trees would fare better, it’s time to call in the experts. There is no one-size-fits-all approach when it comes to planting trees, and you need a customized plan that works best for your needs. The expert arborists at Mr. Tree can advise you on the best course of action and whether self-pollinating trees or cross-pollinating can flourish in your environment. So contact us and watch your garden thrive.