Commercial avocado growers plant their trees in massive groves where they grow more than 60, sometimes 80 feet tall. While Mexico leads the world’s avocado production volumes, this delicious fruit is grown commercially in California, Florida, and Hawaii. Very small volumes are grown in the Lower Rio Grande Valley in Texas.
Because most avocados develop into large trees, you will have to prune your avocado trees quite radically to grow them in a greenhouse. Alternatively, you can grow a dwarf variety that doesn’t grow nearly as tall. Most varieties don’t tolerate cold weather, so it’s important to control the temperature and humidity in your greenhouse.
Can I grow avocado indoors?
Yes, you can grow avocados indoors. In fact, many people grow avocados from the large seed that you find in the center of the fruit.
It’s not difficult to get an avo seed to germinate and it will grow in a pot indoors or outdoors. You can also plant established seedlings in your garden, provided of course you have the space.
But there’s a caveat. When you grow avocado plants from seed, they won’t usually flower or produce fruit.
Also, as the Royal Horticultural Society (RHS) warns, when you grow them as houseplants, which lots of people in the UK do, avocados commonly decline after a few years. They tend to become spindly and their leaves turn yellow.
It’s not easy to maintain ideal growing conditions for an avocado tree indoors. So, it stands to reason that they will decline if they don’t get sufficient light and humidity.
Re-potting declining avocado plants can help them revive.
Sometimes people move avocado plants outside into a warm, sheltered spot during spring, summer, and early fall. Then they bring it back inside during winter.
This is fine when avocado trees are relatively small. But as they grow, you will need to transplant them into larger pots with more soil. Then it can be totally impractical to move them because of their weight.
Can I grow avocado in a greenhouse?
You are likely to have much greater success growing avocados in a heated greenhouse where you can also control the humidity levels. But there are important elements you need to be aware of including the size and height of your greenhouse.
Dr. Mary Lu Arpaia and Dr. Ben Faber, from the University of California Department of Agricultural & Natural Resources, offer advice on growing avocados in a greenhouse.
Because avocado trees often grow very tall, you’re going to have to prune your tree regularly to keep it small enough to grow in your greenhouse. Presuming you buy a grafted tree from a garden center, see if you can find a dwarf or semi-compact variety.
Basic Steps in Growing Avocados in a Greenhouse
You can germinate your own avocado plant from the seed inside the fruit or buy an established plant from your local nursery. The problem with germinating your own plant is that you’ll need to graft a branch from a propagated avocado plant if you want it to flower and fruit. And that’s not easy.
Another factor to remember is that avocados have male and female parts that don’t function at the same time. So for pollination to occur, you’ll need at least 2 types of trees. And because of cross-pollination, you’ll produce fruit that isn’t the same as the seed you started with.
There are two ways to germinate avo seeds. In damp compost or in water.
Germinate Avocado Seed in Water
You will need a wide-necked jar that has sufficient space to accommodate the seed, which should be in a vertical position. Fill the jar with water and push 3 or 4 cocktail sticks into the seed or pip so you can rest it on the top rim of the jar. The rounded end should sit in the water – not the whole of it.
It should take about 6 weeks for it to split in half and for the roots to start sprouting. Soon after, a stalk will start to sprout upwards.
Germinate Avocado Seed in Compost
Soak the seed in hot water (not boiling) water for about 30 minutes. Cut a small piece off the pointed end of the seed.
Fill a pot with moist, sandy compost and push the seed into the pot so that the cut endpoints upwards. Only this flat cut bit should be above the soil.
Place on a windowsill that gets lots of sun and keeps the compost moist. It should germinate in 4-8 weeks.
Planting the Avocado
Once your tiny avocado tree has a few leaves, and plenty of fibrous roots, remove it from the jar and plant it in good-quality potting soil or potting compost. Keep the plant warm and the soil moist as it starts to grow.
Cutting the Shoot
Once your avo plant is 12-18 inches tall, snip off the top 2-4 leaves at the top of the shoot. This will force it to produce lateral branches and bush out.
How to Produce Avocado Fruit
Now for the bad news!
Avocado plants that we grow from seed are usually sterile. For this reason, if you want to grow your own delicious avocado pears, you’ll need to graft a fruiting avo branch onto your homegrown avocado tree.
There are plenty of blog posts on the internet that make grafting avos sound super-easy. But, if you read articles about growing avocados written by university extension officers, you will quickly realize that there’s nothing quick or easy about it.
Dr. Arpaia, who is an extension subtropical horticulturist, states categorically: “Avocados are not easy to graft.”
She also warns that if you’re growing an avocado from seed, it can take anywhere from 5 to 13 years before the tree is mature enough to set fruit. If it ever does set fruit!
Types of avocados you can consider growing in the greenhouse
There are hundreds of avocado varieties. Even though you can control temperature and humidity levels in a greenhouse, it makes sense to consider the local climate.
There are three main varieties of avocado, Guatemalan, Mexican, and West Indian. The first two originated in the mid-altitude highlands of Mexico and Guatemala while the West Indian type originated in the tropical lowlands of Central America and Mexico.
Mexican avocados are regarded as semi-tropical, while Guatemalan is subtropical, and West Indian avocados are tropical.
There are also well-known hybrids including Hass, the main California avocado, which is a cross between a Guatemalan and Mexican species. It has minimal cold tolerance so will only survive in cold areas if it is well protected from freezing.
The West Indian x Guatemalan hybrid, Lula, suffers from severe freeze damage if grown in temperatures below 27 ℉.
Some Mexican varieties have good tolerance to the cold, others don’t.
Indoor Avocado Varieties
Unfortunately, there is no such thing as an indoor avocado variety. If you’re planning to grow your avocados in a greenhouse, all you can do is prune the trees radically or opt for small-sized varieties.
Small Size Varieties
According to the University of California Gardener Program of Contra Costa County, there is only one true dwarf variety of avocado, Wurz. Sometimes called Little Cado, it is a Mexican x Guatemalan species and only grows to about 10 feet.
It does well in a container. But, depending on the height of your greenhouse, you may still have to prune your tree.
Another smallish avocado tree is Gwen, which grows to about 15 feet. But, because it has small limbs, it is easy to prune.
The Holiday avocado is another semi-dwarf variety. It is sometimes called the weeping avocado because it tends to sprawl on the ground.
As suggested above, avocado flowers are very different! They have both female and male organs that function at different times of the day.
So, while all avocado trees are technically self-fertile, the likelihood of self-pollination ever happening is minimal. Rather, this unusual flowering behavior results in inevitable cross-pollination.
This means that you are going to need at least two avocado trees with different flowering types to ensure pollination that will result in fruit. We call the two types A and B varieties. The male organs of the flowers of the one type are functional in the mornings and the female organs in the afternoon. And vice versa.
This is why you’ll need at least Type A and one Type B avocado to get fruit.
How long does it take for an avocado plant to bear fruit?
According to Avocado Production in California written by a bunch of specialist academics, seedling avocados take up to 10 years to bear fruit. Some seedlings never bear fruit.
Grafted trees will bear fruit a lot more quickly than those started from seed. Most will bear fruit in the third year after planting.
A grafted Wurtz, for example, will produce abundant fruit within 2 or 3 years of planting.
Growing avocado trees isn’t particularly difficult. The challenge is to grow avocado trees that produce fruit.
Growing avocado trees in a greenhouse obviate the worry about climatic conditions being right. You can control temperature and humidity quite well in a properly designed greenhouse.
But the height and size of your greenhouse will be of paramount importance. Certainly, if you want a greenhouse-grown avocado tree that is going to bear fruit, there’s a lot of planning that you’ll need to do to get it right.