Avocado Care & Pollination
We find many people are curious how to grow Avocados. Another common question revolves around pollination and fruiting. We decided to add this note to answer some things about growing avocados that are commonly asked.
Growing avocados can be very rewarding. A successful, healthy avocado tree can produce millions of flowers over its lifetime, hundreds of them per growing season. So why then do so many have problems getting their avocados to successfully fruit?
Choose the right variety for your climate. Hass and Pinkerton, for example, will not survive freezing temperatures without frost protection. The below list of avocado variants should be a decent guide as to what temperature a genus will survive down to, but as always take precations when selecting your site based off your properties micro-climate.
In California, avocado trees can be considered self-fruitful. They will produce more fruit if you have an A and a B tree, but you will still get fruit if there is just one, if it survives the winter. Here in AZ where our environment is not as conducive to growing we must take every effort to ensure fruiting.
Avocados require well drained soil and will not thrive in heavy clay soils for long. If you do have heavy clay soils, we recommend planting your avocado tree in a raised bed. The raised bed should be at least two feet above the existing grade of the soil. It is also very important not to plant avocado trees too deeply. We recommend planting them at least l"-2" inches above the existing soil grade and then creating a small mound around the base with a mixture of compost and well drained soil.
Do not over water avocado trees! Over watering trees in the ground in certain soils is often the number one factor in causing root rot. Avocados prefer infrequent deep root watering. It is best to allow trees to dry out before you apply water again. Avocados in containers do need consistent frequent watering.
It is a good idea to apply a minimum of 3 to 4 inch layer of mulch to avocado trees each year to help retain soil moisture and improve soil quality. We recommend however applying at the least 10-12 inches of mulch around the base of your tree if you want to have greater success, and a happier tree. Apply mulch in spring and fall under the canopy of the tree, keep it away 6 inches away from the trunk of the tree.
Avocados should only be minimally pruned in order to shape and control size. Frequent pinching of young trees is a good method to shape the tree, rather than heavy pruning. Avocado trees can be susceptible to sunburn so newly pruned trees and young trees must be shaded until the young trunk is slowly acclimated to sun. As an alternative young trees can be whitewashed with interior white latex paint, diluted 50-50 with water during periods of high summer heat and intense sunshine.
Avocado trees should be fed on a regular basis. Fertilize using well balanced citrus / avocado food using the manufacturer’s recommendations. Avocado trees that have been well feed year-round are better able to deal with our cold temperatures in the winter.
Most avocados you eat are created as a result of cross pollination. The flowers of the avocado tree are refereed to as “perfect”, meaning that they have both the male and female reproductive organs. The blossoms are typically yellow-green and nearly a half inch across. The flowers are born in clusters or “panicales” of 200-300 near the end of the branches. Of these hundreds and hundreds of avocado blossoms, around 5% are sterile. Even with those odds only one to three fruits will develop on each of these panicles.
There are two types of flowers of the avocado tree. These types are refereed to as “Type A” & “Type B”. Each variety of avocado tree will have one or another type of these blooms. Avocado trees bloom in a manner known as “synchronous dichogamy”. This means that the bloom time for the two types of flowers is distinct. Type A female flowers are receptive to pollen in the morning and the male flowers of Type A release pollen in the afternoon. Type B flowers are receptive to pollen in the afternoon and their male blossoms shed pollen in the morning.
This means that for maximum yield you would have best luck planting both Type A and Type B species of avocado tree next to each other to promote optimal fruiting.
Cross pollination of avocados can be encouraged if both Type A and Type B varieties of flowers are present. Both of these avocado varieties need to be blooming at the same time and, of course, you need to have the bees and pollinators around to help fertilize. If you are growing your avocados in a closed, screened or glassed in, inside condition you will need to cross pollinate by hand.
Additionally the temperatures of day & night must be in a suitable range for proper fertilization. Overly cold temps will reduce the number of natural pollinators that will visit your blossoms to carry pollen from flower to flower. Intense wind and rain and other inclimate weather patterns will also keep the pollinators at bay. Cool night time temps are needed to induce blooming. Pollination will most likely occur when the night time temps are in the 65-75 degree (18-23 c) range. As with everything though there is a delicate balance in nature, that, if skewed will decrease success in pollination.
While it is true that seeing as avocado flowers are “perfect”, meaning they contain both male and female flowers and should “self” pollinate, they will fruit better and more successfully if cross pollinated with a different variety. Therefore it is advisable to plant both Type A and Type B avocado trees no more than 20-30 feet apart. A list of Type A and Type B avocados is below.
Type A Avocado Species:
Hass - Largest commercially produced variety with excellent flavor and oil content. Green fruit turns black when ripe, with its recognizable pebbly skin. Fruit size 10-12 oz. Ripens April – September, an extremely long season. Large tree, frost sensitive below 32˚F .
Pinkerton - Heavy, early producer near coast and inland. Green fruit, medium pebbly skin. Great Flavor. Fruit size 14-16 oz. Ripens November -April. Medium spreading tree, Hardy to 30˚F
Mexicola - High quality fruit with thin, shiny black skin. Fruit Size 4-8 oz. Ripens August to October. Cold Hardy to 18˚F
Stewart - A compact Mexicola type avocado. Black when ripe, thin skin fruit. Fruit size 4-8 oz. Ripens August - October. Cold Hardy to 18˚F
Gwen - The fruit is similar to Hass but larger, with dark green skin at ripening time. Creamy gold-green flesh. Medium to large, plump oval fruit, 6-15 oz. Ripens April – August.
Lamb Hass - "Hass-like" Cultivar with black skinned fruit. An excellent new addition! Lamb-Hass is a cross between the traditional Hass and a Gwen (Dwarf) Avocado. Lamb-Hass is a precocious, high yielding, late season avocado with good quality fruit. The tree is upright and compact. Fruit Size- 10-16 oz. Ripens April- November. Longer season than traditional Hass!
Reed - Round fruit about the size of a softball. this fruit can easily weigh more than a pound with thick, green, slightly pebbled skin that is easy to peel. Its flesh is a pale golden-yellow & the texture is buttery. The flavor is bold, rich and nutty.
Type B Avocado Species:
Bacon - Popular variety in most areas of low winter temperature. Hardy to 28 * F. Tasty green fruit with medium thin skin. Medium upright tree. Fruit size 10-12 oz. Ripens December - January.
Fuerte - Excellent fruit quality. Green fruit, medium-thin skin. Large spreading tree. Does not produce well near the coast. Fruit size 10-12 oz. Ripens December -May. Frost tolerant to 30*F.
Zutano - Good variety in relatively low temperatures. Green fruit, medium-thin skin. Upright tree. Fruit size 10-12 oz. Ripens November - January. Used as a pollinator for Hass in orchard settings. (Type B) cold hard to 26*