We have several citrus trees and although we generally get good yields from their fruit, we often wondered how they pollinate. After all, it’d be nice to have more fruit if possible. So, do citrus trees cross-pollinate or self-pollinate?
Most citrus trees self-pollinate, but can still benefit from cross-pollination. Cross-pollination can increase the number of flowers that are fertilized and therefore develop more fruit. There are a few varieties of citrus such as tangerines and clementines that only fruit by cross-pollination.
So, what’s the difference between self-pollination and cross-pollination, and which citrus trees do they include? Read on to find out more.
How Citrus Trees Pollinate
|Cross-Pollinating Citrus||Self-Pollinating Citrus|
|Mandarin Oranges||Navel Oranges|
Citrus trees pollinate either through cross-pollination or self-pollination. The type of pollination depends on the variety. For example, Meyer lemons can self-pollinate, but clementines cannot and require cross-pollination. Let’s take a look at some of the main differences between the two types of pollination.
Cross-pollination is when pollen (male) is carried to a flower (female). When this happens, the flower is fertilized, and the fruiting process begins.
Citrus trees cannot cross-pollinate with other, unrelated species such as plums, cherries, apples, or pears. They can only cross-pollinate successfully with other members of the citrus family.
When it comes to cross-pollination, there are a few different sources that citrus trees can be pollinated from.
- Pollinators (like hummingbirds and bees)
- Manually (by you)
Pollinating animals generally are attracted to the sweet nectar inside of the flowers. This nectar is also commonly their main food source. When these pollinators feed on this nectar inside of the flower, they accidentally collect some pollen on their bodies. If they continue to visit more flowers, the pollen from a previous flower will rub off and pollinate the current flower. If this process is repeated enough times, a tree can produce lots of fruit.
While relying on the wind might seem impractical, trees make up for this by producing A LOT of pollen (if you’ve ever had yellow pollen covering your car in the spring, this is why). This excess pollen is carried through the air and can land in other flowers, starting the fruiting process. However, pollen can only be carried a certain distance by the wind, so if you’re growing multiple citrus plants, it’s best to keep them within 100 feet of each other for the best rate of pollination.
Manual pollination can be done with a small paintbrush, toothbrush, or cotton swab. Simply brush the inside of the flowers gently. As you move flower to flower, they will exchange pollen and start developing fruit. This is especially helpful for cross-pollinating trees that are grown individually in the garden or ones grown indoors (although most potted citrus are self-pollinating).
Cross-pollinated citrus fruit can not only have up to twice the number of seeds, but they also have a chance of developing into hybrid fruits. For example, when tangerines are pollinated with pollen from pomelos, the fruit develops into tangelos.
For this reason, some citrus owners place netting over their trees to prevent pollinators from accessing the plant. This helps ensure the tree will remain self-pollinating and not grow any hybrid fruit.
Contrary to popular belief, citrus fruits that are cross-pollinated from a different citrus variety normally don’t develop any difference of taste, unless it’s a hybrid fruit.
Self-pollinating citrus trees (also called parthenocarpic citrus) have developed a way to create both male and female parts of the flower as one. This makes it so that fruit can develop without the need for a pollinator to carry pollen to the flowers.
For this reason, self-pollinated citrus fruits are generally sterile and as a result, develop little to no seeds. These types of citrus trees can still occasionally be grown from seed, but are most commonly grown from grafting.
However, self-pollinating trees can still benefit from cross-pollination, which can increase their yields by as much as 35%.
Fortunately, many dwarf varieties of citrus are self-pollinating, which makes it easier to keep varieties like Meyer lemons growing in pots indoors. However, even though your indoor citrus tree will likely produce fruit on its own, it can still benefit from cross-pollination. You can place the potted tree outside in the spring to attract pollinators or manually pollinate with a brush and, hopefully, increase the amount of fruit.
And it’s not just Washington navels that can benefit. Limes, grapefruit, and pummelos (all self-pollinating fruit) also show some evidence that suggests pollination can further benefit their yields. This will help prevent citrus trees from dropping fruit that aren’t successfully pollinated or if the tree is overbearing.
Similar to the higher number of seeds from cross-pollination, fruit size can also increase, along with a higher likelihood that the tree maintains a yearly fruiting cycle (and not skipping a season or year).
How Close Should You Plant Citrus Trees Together?
Whether you have self-pollinating or cross-pollinating citrus trees, keeping them close together will increase the likelihood of pollination and the success that the flowers develop into a fruit.
Citrus trees should be planted 10-20 feet apart for the best chance of cross-pollination. However, citrus trees have been known to still benefit from a range of up to 100 feet or more. Generally, the closer the citrus trees are, the easier pollinators can access them and the better rates of pollination they’ll have.
Additionally, planting flowers near citrus trees will also attract more pollinators and further increase the likelihood of pollination.
Most citrus trees are self-pollinating, so you shouldn’t have to worry about going out of your way to help them fruit. However, if you have varieties such as tangerines, clementines, and mandarin oranges, you’ll likely need to plant multiple trees to have successful fruit pollination and yields.
Self-pollinating citrus can also benefit from cross-pollination, so growing different citrus varieties can lead to better pollination rates overall. And who knows, you might end up with some cool hybrid citrus fruits.
For more information on citrus hybrids and pairings, check out this guide by the University of California, Riverside.