Dont Dig Deep Hole for Fruit Trees

Q. I am planting a 15-gallon ‘Wonderful’ pomegranate and suspicious if the plant would benefit from a deeper hole amended with washed sand to help with drainage.

A. Unless there is a drainage problem, 99% of the time there is no benefit from digging a hole deeper. There is even less benefit when adding sand to the hole in any form and this practice is likely to make drainage worse! When drainage is a problem, the simplest method is to plant on mounds.

            The majority of small tree or la
rge shrub roots are about 18 inches deep. That’s all. But the soil they are planted in must drain water or the roots will suffocate or “drown”. To check for drainage, dig a hole to the same depth as the 15-gallon planting container. Fill the hole with water and let it drain. Fill the hole a second time and watch how fast it drains. Filling this whole a second time is very important because the first filling only measures how fast water enters the soil or its “infiltration rate”. Filling the same hole a second time, when the soil is still wet, measures true drainage or its “percolation rate”.

12 year old fruit tree removed and showing the depth of its roots. Most fruit tree roots are about 18 inches deep. So wet the roots to 18 inches on fruit trees like pomegranate.

            If the water in the hole drains overnight, its drainage is acceptable. Only very shallow rooted plants like lawns, vegetables and annual flowers are watered daily during the summer months. When watering trees and shrubs the soil should be drained for at least one day between irrigations. This gives they soil and roots a chance to “breathe” before the next irrigation.

            Take my word on this but adding sand to a planting hole, either as a layer or mixed with the existing soil, is a recipe for disaster. Adobe bricks are made from a mixture of soil, sand and organics. Keep that in mind.