Planting An Avocado Tree
Where to plant your Avocado tree
Avocados need a well-drained soil. In heavier soils they are susceptible to the root disease Phytophthora cinnamomi. Even if this pathogen is not present, the roots can drown if heavier soils get waterlogged. If you are planting a tree in a heavy soil you are better to plant the tree “high” and build well drained soil, mulch or compost up around it. This will allow the soil around the roots to drain if they get too wet.
Avocados prefer a neutral to slightly acidic soil
If you plant in a soil with a lot of limestone you can expect to see yellow leaves with green veins which will need to be treated in an ongoing basis. You can also expect root diseases to be more severe in soil with a high pH.
Avocados can tolerate some shading
Will need a bright spot for good productivity though. Very windy sites will compromise their establishment and productivity. Avocados are one of the most sensitive horticultural plants around to salt. If you don’t have a good water source don’t bother.
Avocados are sensitive to frosts
Either avoid areas that get frost or be prepared to have an action plan for dealing with frosts.
Compost / Mulch
The soils that avocados are commonly grown in West Australia are very infertile. At Avowest when we plant trees in our commercial orchards, we add mulch and compost. Usually we apply large amounts of low-quality mulch in the tree rows then rotary hoe it in.
Spreading mulch before planting
Rotary Hoe it in
When we plant the tree, we add high quality compost to the hole. A little is placed in the bottom of the hole before the tree is planted.
You want to avoid the trees graft union becoming covered with soil
If you do put compost in the hole it may subside with time. You might have to plant the tree a little higher in the ground to allow for this. When the tree is in the hole, add more compost around the side. After the tree is planted, add more mulch to the top to help conserve water.
There is a difference between compost and mulch
Good compost is a basic mulch that has been broken down by microorganisms and will require the addition of artificial or organic nitrogen. There has been a lot of research in West Australia that shows incorporation of compost prior to planting trees will improve the survival and growth rates of avocado trees.
Avocados have surface roots and love mulch additions after planting. Pine bark is an excellent mulch but there are many others. Be cautious with manures. Chicken manure in particularly can have a lot of salt in it.
This video is aimed at commercial growers planting trees but the same principals apply for home gardeners
The single most important thing your tree will need to survive is good irrigation management. You will lose newly planted trees if you don’t water them every day. Your avocado tree will also need regular irrigation if you want to get fruit from it. How much will depend on the site and the temperatures at the time.
The first thing to do after you have planted your trees is to heavily irrigate the site to wash soil particles against the roots and eliminate air pockets. If the water pools for too long you probably have the wrong soil type. Consider raising the tree height with extra additions of mulch around it. This will allow heavy applications of water to drain away from the root zone.
You can kill avocados by irrigating too much
You can kill avocados by irrigating too much. If the water pools on the surface for longer than 5 minutes after irrigation there is probably too much water. Too much water will stop the trees roots from “breathing” and encourage root disease. Many people assume if their tree looks sick that it needs more water. Often this is the worse thing you can do. There are a number of devices available from nursery supplies that can measure soil moisture. At Avowest, we spend thousands of dollars every year in managing equipment to monitor soil moisture. This is the single most important aspect to successfully growing avocados.
At our orchards at Avowest most of the fertiliser is applied through irrigation so we do not usually worry about putting fertiliser in the planting hole.
If you do wish to do this make sure it is not in direct contact with the roots. Because avocado roots are shallow, they are easy to feed with surface applications. General NPK fertilisers are fine but try to use brands that have potassium present as sulphate not chloride. Chloride fertilisers will contribute to salt burn.
Symptoms of salt burn
Root rot (Phytophthora cinnamomi)
Avocados are highly sensitive to Jarrah dieback Phytophthora cinnamomi. It is the main root disease of avocados in the world and is widespread in West Australian soils.
Phytophthora unfortunately has a widespread distribution in WA and you should usually assume you have it. Setting your planting up with correct mulch / compost will help your tree. There are systemic fungicides based on phosphite which are effective if used correctly.
Keep the mulch up after the tree is planted.