PicoBlog

Avocados are a subtropical fruit native to the Americas, originating in Mexico and Guatemala. However, they are easy enough to grow in warm-temperate climates like Melbourne’s (provided you can keep the possums off them).

I live in Kyneton, which has a cool-temperate climate. Most gardeners would say that trying to grow avocados here is ill-advised. But I’m trying anyway. I’ve successfully kept a few avocados alive in the ground for two years now. I’ve also killed a few. I’m yet to harvest a single fruit, but I’ve already learnt a lot in the process.

Our winters are cold, and we have some severe frosts (but it rarely snows). The cold weather can slow the growth and even damage the foliage of the trees, but it’s not the biggest problem I’ve had with my trees.

The biggest killer of the trees has been the heat.

Think about it: an avocado is an evergreen tree. In its natural state it grows in a dense rainforest. Young trees have the protection of an established tree canopy. It is only when the tree grows large and breaks through the canopy that it experiences harsh direct sunlight. Young trees need protection from cold AND harsh sun.

I planted two trees inside my netted enclosure. This is a large space that creates a mild microclimate by reducing wind and increasing temperature. This post on using a thermal imaging camera shows the netting affects nighttime temperatures.

I use internal fencing to create rooms within the netted enclosure. One such room is the chicken run. It is in this chicken run that I’ve planted the avocados.

Apparently, avocados hate root disturbance and therefore aren’t suited to planting in chicken runs. I’ve overcome this by fencing the trees off, so the chickens can’t scratch underneath them. I added poly pipe arches to the structure and have installed 50% shade cloth so that it covers the tops of the trees and the north and west sides. This helps to stop the hot afternoon sun, but allows the more mild morning sun to penetrate. The shade cloth also helps to reduce frost damage.

This protection has not been enough and one of the trees died back to the graft in autumn. The other tree, a bacon avocado, has not put on much new growth at all. So there must be other factors at play.

I planted two trees in the chicken run “room” of my netted enclosure. I was quite specific about which varieties I wanted to grow. The trees needed to stay fairly small, and be cold tolerant. Avocados are divided into two types (Type A and Type B), based on when their flowers open and their pollination behaviour. Avocados need cross pollination from a different type, so I wanted one of each type to ensure successful pollination. Based on various research methods I whittled my list of candidate varieties down to the following:

• Reed (large fruit with thick skin, tree stays fairly small)

• Lamb Hass (upright, compact habit, popular commercial variety)

• Pinkerton (apparently shows some cold tolerance; a small tree)

I had a Fuerte variety (Type A) growing in a pot. According to my research they are very cold tolerant, but grow quite large. So I opted to plant that into the “Avocado Graveyard” (more on that towards the end of this article).

When I went on my fruit tree shopping spree in 2020 I had limited options to purchase avocados. Twin Hives Nursery sold me a fantastic Bacon Avocado tree. It was about 140cm tall.

The best Type A avocado from my wish list was a Pinkerton. It was pretty small, at only about 80cm tall, and quite spindly. I purchased it from another retail outlet.

The smaller Pinkerton tree struggled from the outset. I’m convinced that the best way to grow avocado trees in my climate is to start with large, established trees in the first place. I’ve since sourced a large Reed avocado from Twin Hives Nursery and have just planted it in the place of the Pinkerton.

Timing of planting is critical to avocado success. Winter is too cold and the trees will languish. Summer is too hot and the trees will become scorched and heat stressed. Plant them in spring, as the soil warms up. This gives them an opportunity to establish before the onset of summer. Aim to plant avocados at around the same time you plant your tomato plants.

Usually, I treat my fruit trees harshly. This results in a small but very productive tree. For the first two years, my main two avocado trees were on the same watering zone as the rest of the deciduous fruit trees. This meant they were watered via two drippers (each 2 litres per hour) for 40 minutes once a week.

Last year, I noticed that this wasn’t enough for the avocados and I needed to get the hose out regularly to top up the soil moisture. I think this lack of water may have contributed to the dieback of the Pinkerton avocado. The Bacon avocado struggled, lost a few leaves, but bounced back in autumn.

This year I have upped the watering regime. I’ve re-configured the irrigation, so the avocados are now watered as part of the berry patch zone. This zone is activated for 20 minutes every three days in the warmer months.

I have also added a length of drip line at the base of each tree. For example, the Bacon tree now has an extra 13 drip holes. This should equate to lots more water, more often, for each tree. I did the maths and it works out at around 10 times more water by volume per week for the tree.

I’ve also added a thick layer of mulch under each tree to help retain soil moisture and regulate the soil temperature.

Our native soil is sandy and lacking most nutrients. I use this to my advantage to help keep my fruit trees small. When I planted the trees, I didn’t incorporate much compost and just planted into a mound of predominately native soil. This mound is designed to keep the roots out of waterlogged soil during wet winters. This strategy was successful, as our very wet spring of 2022 didn’t kill the trees.

However, I think that the avocados are struggling with a lack of nutrients. So this spring I’ve added lots of compost and chicken manure. I dug this through the mound before planting the new Reed avocado.

Essentially I’m finding that avocados are a lot like citrus trees and should be treated the same way. They hate cold, they hate hot, they hate wind, they hate dry soil, they hate waterlogged soil, and they need just the right amount of soil nutrients, but probably hate heavy or inconsistent fertilising.

I’m hoping that increasing watering and soil nutrients will help stimulate a lot more growth of the avocado trees.

I like to experiment in the garden. It helps me understand plants, optimise success and find new ways of doing things. The big storm of 2020 tore down a few trees in one section of my property. I decided to use this opportunity to experiment with evergreen trees, particularly avocados.

My team of interns and I decided to see how many avocados we could kill in quick succession. Killing avocados would help us work out what not to do!

We started planting seeds from store-bought avocados. Some were propagated in pots in the greenhouse, others sown directly. Once planted into the avocado graveyard, they were all irrigated using an automated drip system.

The avocado graveyard was surrounded by large established trees. A shed protected one area from frost rolling down the hill. Some areas had morning sun, some had afternoon sun. Other areas were shaded by trees for most of the day. None of them had mollycoddling protection like the two in the netted enclosure do.

Two years later and very few avocado trees are still alive. A few are doing okay, though. Here’s what I learnt from the experiment:

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