Free-draining, slightly acid soil is essential as avocados are very prone to root rots. Even waterlogging resulting from a freak storm, that drains in just 48 hours, can kill your tree. Extremely frost sensitive when young, they also need to have a sheltered position away from prevailing winds. The young bark can be killed by sunburn, so screen it from hot afternoon sun or paint the trunk with white water-based house paint. Once established avocados can tolerate down to -6°C for short periods.Avocados have a shallow root system so a good layer of mulch is essential, as is a plentiful water supply in the dryer months. Like citrus fruit, avocados like plenty of nitrogen, pelletised chook manure is ideal from early summer when the fruit is setting.
Pruning and training
Avocados will naturally grow into large trees, which can make harvesting difficult. So gardeners should prune them back to 2-3m picking height each year. If you don’t regularly prune and you have a large tree, they can still be pruned right back to a few branches, which will re-sprout from dormant buds.
This will lead to leaf and stem growth with no fruit for some time. Pinching out new growth from an early stage is best. Keep the centre of the tree open to discourage fungal diseases. Prune for shape after the fruit has set.
Avocados can be ‘stored’ on the tree. The fruit will not ripen until after it has been picked, so you can choose – within reason – when to harvest your fruit. Hass avocados last the longest, and can stay on the tree from November to April. However, if you leave mature fruit on the tree beyond a few months, your avocado may tend to biennial bearing, that is, only cropping every two years.
Pollination and Fruiting
There are differing opinions on the need for cross pollination with Avocados. Avocados are classified into ‘A’ and ‘B’ type cultivars (see below). Both types can be self-pollinating, with the aid of insects.
Under most variable spring conditions, there is a time when there are both male and female flowers present on the one tree. This ensures self-pollination as long as temperatures do not drop below 10ºC.
‘A’ types are more tolerant of cooler climates and pollinate at lower spring temperatures. Only where there are constant temperatures at flowering that do not drop below 20ºC in the day, and 10ºC at night should both ‘A’ and ‘B’ cultivars be planted to ensure a crop.
Flowering occurs in spring on new growth. Subsequent fruit should be thinned. Fruit takes up to 12 months to ripen, so both flowers and fruit can be present on the tree at the same time.
Choose ‘A’ types for cooler regions.
- Hass ‘A’ type: The best backyard variety with excellent flavour and thick, black, warty skin. A tall upright tree.
- Reed ‘A’ type: More like a small cannonball than an avocado, this early-bearing upright tree flowers in late spring – ideal for areas with cold, wet springs.
- Wurtz ‘A’ type dwarf: The smallest-growing of all avocados that can be grown in a pot. Producing delicious, green pear-shaped fruit on weeping branches.
- Bacon ‘B’ type: Quick growing, cold-tolerant, upright trees that bear fruit at an early age. The thin skin is prone to fruit fly attack.
- Fuerte ‘B’ type: Classic pear shaped, thin skinned fruit on a wide spreading tree. Best in warmer climates.
Tips on growing
- Birds are not a problem for avocados, so there is no need to net your tree, and they suffer fewer pests than apples, making them the best value backyard fruit tree.
- A few weeks prior to planting, improve your soil by digging through a mixture of well-rotted manure and blood & bone.
- Citrus do not need pruning, but it can improve crop development.
See more on Avocado planting and harvest time.