How do I prepare rocky soil for planting an avocado tree?

Question

I would like to plant some avocado trees in my garden. The soil seems very stony (<3cm in diameter stones on average, but a couple of bigger ones) and they go down at least 30 cm.

Do I need to do anything to the soil in preparation for the fruit tree? Will it be okay with the stony soil or should I remove the stones within a certain distance?

The research I have done mainly talks about removing stones from flower beds but not bigger plants like trees.

The tree is about 1m tall and was home-grown by my dad. He lives in another part of the country but there are simmilar soil conditions there. There are other avocado plants in the area. A neighbour has a couple too, I believe. I live in Swellendam, South Africa. This is a map of the soil in the country:

I live in the bottom left province where the soil conditions are mostly red and green:

Answer 1

What a beautiful city you live in! Avocados are grown around the world and are very adaptable. South Africa produces over 80,000 metric tons of avocado every year. The Western Cape area where you live is a large grower.

Avocados come in different varieties and it would helpful for you to find out what kind it is. Each variety copes better with different conditions. You can start diagnosing what type you have with this tip:

• The leaves of West Indian varieties are scentless
• Guatemalan types are rarely anise-scented
• Mexican types have a pronounced anise scent when crushed.

The best procedure for planting trees is not to amend the local soil. If you have large stones then remove them from the planting pit if possible. Do not add soil that is different from the soil you dug out of the hole.

This article is very specific to the requirements of avocados in South Africa.

• Watering: All avocado cultivars that are grown commercially in South Africa are known to be sensitive to water stress...supplementary irrigation during this [flowering] period is essential.
• Best soil types: Only reddish-brown, red and dark-brown soils, particularly in the subsoil, are suitable. Temporary to permanent waterlogging with concomitant root rotting usually occur in yellow, grey, light-brown and white soils. Very dark and black soils usually have either a high clay content that could lead to poor root development, or a large percentage of organic matter that can lead to excessively acid conditions and aluminium toxicity.
• Planting: Holes at least 0,6 m deep and wide are prepared well in advance ... After the young plant is put into place mulch is beneficial, weeds should be controlled, and watering is necessary until the roots are well established
• Location: Avoid Cold pockets [which] will occur in low-lying areas such as the bottom of a valley. A warm sunny place which is sheltered from the wind is best.
• Fertilization: for young trees after one year of growth, using a balanced fertiliser, four times a year. This changes as the tree ages and starts to fruit
• Pests and diseases:
  • Rats and squirrels will strip the fruit. Protect with tin trunk wraps. Leaf-rolling caterpillars (Tortrix and Amorbia) may destroy branch terminals.
  • Avocado brown mite can be controlled by powdered sulphur. Six-spotted mite is very harmful; even a small population can cause large-scale leaf shedding.
  • Two fungi and one virus cause more damage than any other pests.Dothiorella (Botryosphaeria ribis) canker infects the trunk, causing dead patches that spread to maturing fruit, causing darkened, rancid smelling spots in the flesh.
  • Mexican types are immune to trunk cankers but the fruit is not.
• Other tips:
  • Current orchard practice avoids staking. The best results are obtained by fencing the tree with plastic mesh for the first two to three years.
  • The skirts of avocado trees are sometimes trimmed to discourage rodents otherwise the trees are usually never pruned.
  • It is better to avoid any pruning.