Robin Gale-Baker, from Sustainable Macleod, discusses growing avocado trees. This is one of a series of articles she has written about growing fruit trees (see right hand sidebar). She has also written a number of articles about growing various vegetables, growing various herbs and general growing techniques.
Have you ever considered that when you buy an avocado you could be supporting a Mexican criminal cartel or supporting water rights in Chile that are resulting in thousands of small farmers being effectively deprived of their livelihoods?
Mexico is the biggest producer of avocados in the world, having a perfect climate for production. The industry has, however, apparently been controlled by cartels since the late 1990s. Avocados have become a new conflict commodity, much like conflict diamonds, as cartels illegally log, clear land and murder small farmers.
Chile is the 14th largest producer of avocados in the world. Chilean economists in 1981 adopted an ‘American’ water rights system (much like the Australian one) that has left smaller farmers asking the world to stop buying Chilean avocados. These farmers are not getting a water allocation at all and, not only are they going broke, but they are also unable to use their land for anything else.
What better argument could there be for purchasing local food or growing your own?
Avocados are tropical trees which do well in warm, humid climates with little temperature variation. Sudden drops in temperature and frosts are very damaging to the fruit.
There are, however, varieties that can grow in temperate zones such as ours. Wurtz ‘A’ Type is one. This grafted ‘dwarf’ grows to 4 metres in height and 6 metres in width. It has a weeping habit, medium sized fruit and can be pruned down to 2 metres. It flowers and fruits from November to February but takes at least 3 years to produce. It is partially self-fertile but will fruit better if a type B cultivar is planted nearby (e.g. Bacon, Fuerte or Sharwill).
[Editor’s note: when an avocado flower blooms, it does so with either its female reproductive parts available or its male reproductive parts available, but not both. With the Type A varieties, the female parts tend to be available in the mornings, with the male parts then becoming available in the afternoons (with the female parts becoming unavailable). With Type B varieties, it is the other way round. This process is ‘designed’ to hinder self-fertilisation.]
Wurtz can be grown in a large pot (75-100 litres). This is often a good way to grow an avocado as it means that in winter, when the tree needs protection from frost, it can be moved to a sheltered spot. Alternatively, build a semicircular mud brick wall around it and the thermal mass of the mud brick will keep it free from frost damage.
Avocados are shallow rooted and have a weak root system. They are best grown on a large mound or a slope as they need to be well drained. They also need plenty of water (it takes about 68 litres of water to produce one avocado in tropical climates, a bit less in temperate ones). They are easily stressed by dryness, windburn or sunburn and (unusually) like being watered in the middle of the day. Trunks can be protected from sunburn with whitewash. Stake the tree to prevent breakage or loosening from the soil in wind.
In our clay soils, it is best to add gypsum, compost and well-rotted cow manure and some blood and bone to the soil, and build a high, wide mound. Then mulch it well to keep moisture in the mound but keep the mulch away from the trunk to prevent collar rot.
Avocados are climacteric, meaning that they ripen off the tree. Once an avocado has reached full size, twist it from the branch and let ripen it for 2 weeks. If it does not shrivel, then the fruit is ready and all can be harvested or some left on the tree for later use.
[Editor’s note: I have been trying to grow avocados for a number of years. For a young tree to survive, it needs protection during both the Winter and the Summer (I use shade cloth). I have never solved the problem of all the fruit dropping off the tree when still minuscule.]