self & cross pollinating olive trees

Self-pollinating & Cross-pollinating Olive Trees

Depending on the olive variety you choose, some olive trees are self-pollinating and some require a pollinator. Self-pollinating olive trees include Arbequina, Koroneiki, Fantoio, Coratina, Picual;  whereas olive trees that require pollinators include Manzallino, Mission, Sevillano.

Olive trees requiring a pollinator may seem like additional work, however, cross-pollination generally improves the fruit set especially when environmental conditions are not optimal. Even so, if it is a self-fruitful olive cultivar, it increases flowers and fruit development by cross-pollination.

In this article, you will find relevant information about self-pollinating olive trees, varieties requiring cross-pollination, and an olive tree pollination chart.

koroneiki self pollinating olive tree
This is the Koroneiki variety self-pollinating or self-fertile olive tree growing in our grove in Kalamata, Greece

Self vs Cross-pollinating Olive Trees

Self-pollinating or self-fruitful or self-fertile olive trees

They do not need other olive varieties to grow next by, a single olive tree is pollinated by the wind or bees. As a result, will bear the olive fruits all by itself.

Therefore to obtain a maximum olive yield, it is necessary to associate self-fertile varieties with others that are also good pollinizers. For example, self-pollinating olive trees can benefit from cross-pollination that can increase their yields by more than 10%.

Cross-pollinating or self-unfruitful olive trees

They need another tree or sometimes two other trees for complete pollination. They should not be the same variety, but a different olive tree variety.

Generally having 2 or more different compatible varieties growing in close proximity 100 feet (30 meters) will facilitate adequate cross-pollination.

Good thing, when olive trees are cross-pollinated (even if it is unnecessary) you benefit from a higher probability of pollination, bigger fruits, and a higher crop yield of 10% or even more. 

self pollinating olive trees 3
In a year with a normal flowering, 1 to 2% of fruit set is enough for a commercial yield. In “off” years, when flowering is weak, fruit set may increase to 10% with cross-pollination. Normally one fruit per inflorescence develops, except for some cultivars with small fruits such as Koroneiki and Arbequina (source)

For example, the Manzanillo olive tree may be best pollinated by a Sevillano or Barouni olive variety in order to get heavy crops. Though Ascalono and Mission could also pollinate Manzanillo but with lesser results in crop yield. Also, they all have to blossom at about the same time.

Also, the presence of an occasional Manzanillo tree will increase the yields in a Sevillano orchard. For this reason, olive tree growers plant several rows of Sevillano and then a row of Manzanillo to achieve a heavier crop.

Italian origin Frantoio cultivar cross-pollinated with occasional Pendulina cultivar may increase crops by up to 10%. It is sufficient to plant only 5 – 10% of the total orchard’s trees as Pendulina for successful cross-pollination.

Self-pollinating Olive Tree VarietyOrigin Country
AmfissaGreece
ArbequinaSpain
BarneaIsrael
BosanaItaly
CoratinaItaly, Croatia
CornicabraSpain
FrontoioItaly
HojiblancaSpain
KalamonGreece
KoroneikiGreece
PicholineFrance
PicualSpain
SevillanoSpain, California
Table 1. Self-pollinating olive varieties

When & How Olive Tree is Pollinated?

The olive tree pollination happens in spring when the trees blossom. Though olive trees can not pollinate with other unrelated species such as citrus, they can only pollinate with other olive cultivars.

Pollen from the anthers (the male part of the olive tree flower) has to be transferred to the stigma (the female part of the olive tree flower). Only if the olive tree flower is pollinated successfully, the flower is fertilized and the olive fruit process begins. Else, an olive flower is blooming, but not fruiting afterward.

When it comes to olive pollination, there are few different sources that olive flowers can be pollinated from:

  • Pollinators (like bees and birds)
  • Wind
  • Manually (by person)

Pollen wind role is very important to not only spread and diffuse pollen grains but also transfer them fast to reach stigma before they lose their viability.

Pollinating insects feed on the nectar inside olive flowers and accidentally collect some pollen on their bodies. Then continuing to visit more flowers, the pollen from the previous flower will rub off and pollinate the current olive flower.

Manual pollination for your olive trees can be done with a small paintbrush, toothbrush, or cotton swab. Simply brush over the small olive flowers gently. As you move flower to flower, they will exchange pollen and start developing olive fruit. This is especially helpful for cross-pollinating olive trees that are grown individually in the garden or ones grown indoors.

self pollinating olive trees 1
Although olive flowers are wind-pollinated, they are visited by insects including honeybees, which may help pollination

Also, if an olive tree flowers do well in spring and do not set any fruit afterward, it may be an indicator that your tree needs a cross-pollination with a cross-compatible olive cultivar.

Read more about olive tree flowers and

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Find out reasons why olive trees not fruiting

Why My Olive Tree Is Not Pollinated?

There are multiple factors that can interfere with pollination. Let’s look into several of them:

Olive variety compatibility

If your olive tree is cross-pollinating, you should ensure to plant other varieties compatible with your own variety. Also, they all have to blossom at about the same time.

For example, Frantoio and Koroneiki olive trees are not compatible with each other. Similarly, Manzanillo and Mission trees are not compatible with each other.

self pollinating olive trees 2
If olive tree variety is not self-compatible or self-fertile it is recommended for the growers to plant more than one cultivar in their orchard to guarantee a good fruit set

Environment conditions

Lack of rain or too much rain; high or hot dry winds; spring frost can damage flower buds before they blossom or can be detrimental to pollination during the flowering season.

Also, excessive winter cold or even late-spring frost can kill flower buds and blossoms. For this reason, it is important to choose the right olive tree variety for your climate zone.  

For more information read our article on where do olive trees grow best.

Different Length of Blooming

The different length of blooming when olive flowers get pollinated depends on variable environmental conditions such as temperatures and rains.

For example, the blooming period may be short due to high temperatures with a lower possibility of cross-pollination. It can start early in spring since thermic conditions are favorable but end up when heavy rains start. Another scenario for a longer blooming period is mild temperatures and frequent but low rains.

Pests and Diseases

Pest and diseases can be problems for olive flowering and pollination. Not treated olive trees on time may end up losing all flowers and fruit sets.

Fertilize prior Pollination

Prior to the spring olive flower and fruit developing season, feed your olive tree with nitrogen and potassium for better crop results. Use only organic fertilizers and natural pesticides if needed.

If you are not sure about the soil condition, it is recommended to test your soil at least once in 2 years in order to ensure relevant nutrition for your olive trees.

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Read more about olive tree fertilizers & nutrients

Olive Tree Pollination Chart

The dynamics of compatibility in olive varieties are somewhat complex, and many varieties even self-compatible require cross-pollination for a better fruit set.

This is not an exhaustive olive tree pollination chart with main varieties used for cross-pollination:

olive tree pollination chart v2 1
Infographics 1. Olive tree pollination chart

Under optimal weather conditions at the flowering season with cross pollinators, you can achieve maximum crop yield results.

Final Thoughts

When you are searching for an olive tree ready to plant in small spaces, consider self-pollinating olive trees varieties in order to enjoy olive harvest every autumn. In case you have the opportunity to plant several olive trees, pick compatible varieties and improve crop yield.

About the inter-compatible olive cultivars the best to discuss with a local agronomist or local farmer cause it depends on overlapping factors such as blooming, pollen compatibility, and environmental conditions. Knowledge on self(in)compatibility is important for the olive tree growers to allow them to better manage newly introduced cultivars in their orchards and for choosing suitable pollinators among the local olive cultivars.

Also, if you have space for other trees to cross-pollinate your olive tree and get a higher crop yield. For example, olive trees should be spaced between 6 feet (2 meters) for a high-density grove or 18 feet (5 meters) for a traditional grove.

Plant the olive tree where fallen fruit won’t cause a problem – away from decks, driveways, and walkways. Otherwise, get a fruitless olive tree or learn 5 ways to remove olive stains from concrete on pathways.

Sources

Olive bloom and pollination by University of California

Cross-pollination in olive cultivars – RIRDC publication

Self-incompatibility and pollination relationships for four Greek olive cultivars

Self-sterility and cross-pollination responses of 9 cultivars in Central Italy

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