How to Grow Avocados in a Greenhouse: A Step-By-Step Guide

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To grow your avocado in a greenhouse, you must germinate it initially, cut off the tip of the plant shoots, and then plant it in well-drained soil. Move on to graft a scion onto your rootstock while ensuring proper care for the plant. Finally, you must cross-pollinate your avocado tree to make it bear fruit.

A much more in-depth and step-by-step process will be covered in the following sections, so read on.

Avocados – an introduction

Avocados fruits grow from trees that are said to have originated in south-central Mexico. Avocados are considered to be large berries containing a large seed at the center of their fruit.

Avocado fruit on the tree

I use color as my chief guide. But I always squeeze an avocado – you want the fruit to feel close to the skin. If you can feel a separation, the avocado is past its prime. The avocado should have a little give, but not much.

Dorie Greenspan

Over the last 20 years, the US has accounted for a 443% increase in consumption of avocados throughout the years, starting from 1.6 pounds in the 1995s and reaching 7.1 pounds in 2015 (source). This shows how much there is a need for more of this fruit.

A Step-By-Step Guide to Growing Avocados in a Greenhouse

There are several steps to ensuring proper growth for avocados, and we will be unpacking them step by step and the needed tips for its growth.

1. Seed Germination of avocados

Germinating avocado seeds is exciting and fun. You get to see the roots and shoots growing from the pit. This is how you can germinate an avocado seed:

Clean the avocado Seed

Soak the seed in water for a few minutes to clean the seed. Make sure that you do not peel out the brown skin. The brown skin is the seed cover, protecting the embryo from bacteria and fungi.

Locate the Top and Bottom Parts of the avocado Seed

A side of avocado seeds is usually pointed, and their top/bottom sides are easily recognizable. The top is the side pointed up, while the bottom is flat.

Before we get into the details of how to grow avocado in a polytunnel, I made a video showing you how to do it and the many methods. The video and this article will have you growing them like a pro.

Hang the avocado Seed in a Glass of Water with Toothpicks

Pin three toothpicks at the bottom angle of the seed. Using the toothpicks, hang the pit on a jar of water. The pit should be half-submerged. Always add more freshwater so the base of the seed will remain submerged.

Within two to eight weeks, you should notice that the seed is splitting and a tap root has emerged from within. Always add fresh water. You should also notice a shoot growing from the top of the seed.

Eight weeks are enough for avocado seeds to germinate. If you do not notice any growth after eight weeks, try the process with another seed. When your seed has germinated, move on to the next step.

2. Cut Off Half of the Shoot of the avocado plant

growing avocado with toothpick method

When the shoot reaches a height of 30cm, cut 15cm off.

Cutting off the shoot is essential because it helps you identify a healthy plant (with established roots) and makes the avocado bushy instead of growing tall.

3. Plant the Avocado in Your Greenhouse

When a new set of leaves have grown, transplant the stalk into a large pot or on your greenhouse soil, the tip of the seed should poke out of the soil. The soil should also be moderately rich and well-drained.

When watering your avocado, constantly water when the soil becomes dry; avocados grown in a greenhouse are not watered as often as those planted outdoors. Do not use inorganic fertilizer and instead opt for peat moss or compost.

4. Graft a Scion onto The Rootstock of your Avocado plant in the greenhouse

Avocado trees planted from seeds are sterile, which most don’t know. To get a tree that produces fruits, you will need to graft the branch of a propagated tree onto your avocado.

When your avocado shoot is two feet tall, graft a scion (i.e., the branch from the propagated tree) onto it.

The scion should be grafted properly so water and nutrients can flow from the rootstock (i.e., your plant with already established roots) to the scion.

After six months to a year, or when the roots of your avocado have covered the pot, transplant the young tree into a large pot (which will be its permanent pot). Continue watering as instructed above, and add fresh compost or slow-release manure to the plant.

5. Provide Regular Care to your avocado plant in the greenhouse

How can you care for your Avocado in your greenhouse? Here are some valuable tips:

The temperature of the greenhouse is essential to check for fostering avocado plants

Avocados are tropical and subtropical trees. To grow and produce fruits, avocado plants need 15°-29°C (60°-85°F).

In temperate places like the UK, the USA, etc., planting avocados in a greenhouse is more advantageous than planting outdoors because a greenhouse traps atmospheric temperature (i.e., the inside of a greenhouse is warmer than the average temperature outside the greenhouse).

Since it is easier to regulate the temperature in a greenhouse, greenhouse avocados survive during winter. Unless you are lucky enough to have a cold-hardy variety, your avocado will not be able to survive winter or frost.

Avocados Love a Humid Greenhouse

The humidity in your greenhouse should always be above 50%. Avocados cannot survive in an environment with less than 40% humidity.

Growing your avocado in a greenhouse is more advantageous than planting outdoors because greenhouses trap water vapor lost by evaporation or transpiration. The vapor trapped by greenhouses increases the humidity of the room.

If the average humidity in your greenhouse is below 40%, look into installing a humidifier.

Watering Avocados in the greenhouse

watering avocado plants indoors

Do not overwater your tree. Avocados can get root rot when they are overwatered.

In a greenhouse, water loss by evaporation and transpiration (i.e., water lost from a plant leaf) is reduced. You should water your greenhouse avocado only when the soil is becoming dry and make sure that the soil is well-drained.

How to Get a Bushy Avocado in the greenhouse

Outdoor avocado trees can grow up to 40 feet tall, while indoor-grown counterparts can reach about 20 feet.

A trick that can reduce the height of your avocado tree into a bushy-like plan would be to cut off overgrown branches and leaf petioles.

When a branch is cut off, the plant grows more branches scattered in different directions from that point. This stops your avocado from growing tall and gives it a bushy appearance.

Fertilizing Your Avocado Tree in the greenhouse

Generally, trees like avocados do not require excess fertilizing since they grow and produce fruits slowly.

Fertilizing your avocado depends on the type of potting mix ratio. Add more compost or slow-release fertilizers to the pot if you have more sandy soil.

Earthworm castings are also known to be beneficial to your avocado. If you can, introduce earthworms into the pot, as they will hasten the decomposition of your compost while providing your tree with nutritious castings.

6. How to Pollinate Your Avocados in the greenhouse

bee on yellow flower

Avocados are entomophilic plants. This means that insects pollinate them. You can also look into cross-pollinating it with another avocado tree.

Pollinating avocados is complex and confusing for people not experienced with avocados or growing avocados in greenhouses. Hopefully, the tips below will help you learn about this process more clearly.

Plant More Than One Avocado Tree in your greenhouse

Except if you are growing your avocado in a region where avocados are popularly cultivated, you will need to grow more than one avocado tree if you want your tree to bear fruits.

When there are multiple avocados in an area (in this case, a greenhouse), your trees have better chances of producing fruits.

Consider Introducing Insects to aid in Avocado tree Pollination in your greenhouse.

Avocados are entomophilic, so you must either take your plants to anthophilous insects (i.e., insects that pollinate plants) or bring pollinating insects to your plants.

Examples of pollinating insects for avocados would be bees, butterflies, wasps, etc.

To produce more fruits, you can hire bees from a local beekeeper or take your avocados outside when they are flowering.

7. Growing and bearing of fruits period for avocado plants in the greenhouse

Note that avocados can take five to ten years to produce fruits. During the said period, you should add fresh compost into your pot yearly and continue watering as instructed above.

Types of avocados you can consider growing in the greenhouse

cut in half avocado showing the pit

The different varieties of Avocados are grouped into two types: Type A and Type B.

Type A avocados open the stigma (i.e., the female part of their flowers) in the morning, then the anther (i.e., the male part of their flowers) later in the afternoon, while in contrast, Type B avocados open their anthers in the morning, then their stigmas later in the afternoon.

The difference between the types of avocados implies that the chance of your plants producing fruits is more when different types are cross-pollinated.

Cross-pollinating different types of avocados is why offspring avocado plants are sterile (i.e., they cannot produce fruits).

Examples of Type A and Type B avocados will be given below:

Type A and Type B Avocado Varieties

The table below lists the varieties of Type A and Type B avocados.

Type A VarietiesType B Varieties
Gwen Fuerte
StewartSir Prize
Lamb HassWinter Mexican  
Carmen HassWilma (aka Brazos Belle)
Opal (aka Lilas)
Mexicola Grande
Pryor (aka Fantastic)

We will also be introducing cold-hardy varieties that can be grown in temperate regions in the next section.

Cold-Hardy Avocado Varieties

The table below contains avocado breeds, their type, and the least temperatures they can tolerate. When growing your avocado tree, it is best to grow the trees in warmer temperatures.

BaconB-7° to -6°C (20°-22°F)
BrogdonB-4°C (24°F)
FantasticA-9°C (15°F)
FuerteB-1°C (30°F)
JoeyB-9° to -8°C (15-18°F)
Mexicola GrandeA-8° to -7°C (18-20°F)
OpalA-6° to -4°C (22-25°F)
WilmaB-9° to -8°C (15-18°F)
Winter MexicanB-6° to -4°C (22-25°F)

There should be more than enough avocado types to look into growing and fostering in your greenhouses with the lists above.

Benefits of eating avocado fruit

avocados on white table with seeds and leaves

It is widely loved because it is rich in nutrients and has beneficial fats for managing and lowering cholesterol levels.

They are also known to aid in good digestion and level blood pressure due to their potassium content and contain about 41% of the daily needed folate intake to help prevent congenital disabilities during pregnancy (source).

Avocados are challenging to grow outdoors, so most people foster them within greenhouses. The next section shall cover the step-by-step process of doing that.

FAQs on How to Grow Avocados in a Greenhouse: A Step-By-Step Guide

How do you send more water and nutrients into the avocado scion?
If you find branches growing below the scion that you grafted onto your rootstock, cut them off. These branches will compete with the scion for nutrients and water. The branches below the scion are grown from the original plant (i.e., your rootstock) and will not produce fruits.

How do you protect your avocados from pests?
Your greenhouse-grown avocados will not have as many pests as those grown outdoors. To combat pests from attacking your plants, introduce predatory insects like ladybugs, consider getting insecticides, and ensure that your plant is pest-free before taking it indoors (after pollination).

Why are Avocado Roots Poking Out of the Pot?
If the roots of your avocado tree are poking out of the pot, it means that your pot is too small. Consider repotting the tree into a bigger pot or transplanting it to the greenhouse soil. Remember that avocados need well-drained soil, so make sure the pot has holes for drainage.

Should You Grow Avocados from Seeds or Buy from A Nursery?
If growing avocados for commercial purposes, get an already-grafted avocado from a nursery to lessen grafting mistakes. Also, get one from the nursery if you don’t want to foster it from its germination phase. If you are growing it for fun, grow it from a seed to get the full experience.

How Can a Subtropical Avocado Be Grown in a Temperate Region?
It is possible to grow avocados in temperate regions. Some cold-hardy varieties are specifically bred to withstand the low temperatures of a temperate region. You can also utilize a greenhouse to regulate the temperature to suit the plant’s required 60-85 F.

Conclusion on how to grow Avocados in greenhouses

Avocado fruits have many great benefits for health and taste good, making them a very sought-after fruit. Due to this peak demand, countries like the US have also been importing about 80% of these fruits worldwide to meet consumer needs (source).

With you being an aspiring gardener, instead of buying them, hopefully, with this information and tips, you can now look into growing them yourselves in your greenhouses and be proud that you were there every step in its growth process.

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