Match the tree to the soil
If you’re not sure what kind of soil you have or its properties, there's a great online resource you can use – for free – to find out.
The Visual Soil Assessment (VSA) field guide has comparative pictures and notes that teach you how to grade your soil. It's fun (to me) to look, sniff and feel soil, and all you need is a spade.
You can choose either Volumes 1-2 (flat to rolling land) or Volumes 3-4 (hill country): www.landcareresearch.co.nz/ publications/vsa-field-guide/
1 test to do before you start
If you have clay soil or a hard pan (a hardened layer of soil) within 1m of the surface, dig a hole and fill it with water late in the day. If the water doesn't drain away by morning, you need to find another location for your tree. If it's a hard pan, dig through it until you reach free-draining soil.
Know your soil moisture
Most fruit trees prefer their roots to be moist but not waterlogged. There are exceptions, such as persimmons and figs, which are more tolerant of having wet roots than most fruit trees. Conversely, the roots of the avocado are susceptible to the fatal root rotting disease (phytophthora) in moist soil. If you have free-draining soil or soil prone to drying out: plant in a depression or, if on a slope, on a terrace or swale that holds the water and directs it to the roots. If your soil gets boggy in winter: create a mound of soil and plant into that. Most roots are in the top 30cm of soil, so it doesn't have to be a high mound to be effective. Even 10cm of height will give the uppermost roots air and can be the difference between life and death.