Fruit Trees and the Benefits of Wood Mulch

Q. Could you provide me with a copy of the mulch trial you conducted on fruit trees several years ago? You randomly applied mulch to different fruit trees and grew some without mulch. I lost this information.

This is a picture of the mulch trial performed at the University Orchard in North Las Vegas. A variety of fruit trees were planted with and without 3 to 4 inches of wood mulch at their base. They were all watered and fertilized the same. Mulch was wood chips made from trees that were removed from residences. Mulch was donated by First Choice Tree Service.

A. I conducted this mulch trial in 2009 – 2011 with the First Choice Tree Service on bare root fruit trees planted in our desert soils according to my specifications using 50% compost mixed with raw desert soil in a volume to volume ratio.

Look at the change in soil color after a very short time when wet soil is covered with woodchip mulch. The wood chips "melt" into the soil with time, decomposing and adding nutrients, stimulating microorganisms and make a healthy environment for earthworms.

            Mulch is a layer or blanket applied to the surface of soil. Mulch can be made from wood, bark, rock, newspaper, cardboard or even plastic. But if this is applied to the surface of the soil and left undisturbed, it is considered mulch.

This is Redwood decorative bark mulch. Bark mulches do not provide the same nutrients as woodchip mulch which is much better. Would chip mulch is made from the entire tree, not just from the bark.

            A 50% mixture in a volume to volume ratio, means, for instance, a 5 gallon of compost mixed with a 5 gallon bucket of raw desert soil. In a few months of watering this results in a raw desert soil with less than 1% organic matter increasing to between five and 10%, not 50%. If you want to know why, attend some of my classes.

            Peaches, plums, pluots were planted in holes about 3 feet wide and deep enough to accommodate their roots and no deeper. The holes were not deeper than this because water added to planting holes drained water in less than six hours.

This fruit tree was covered with a layer of rock mulch about 2 inches deep. Organics that were added to the soil at the time of planting will be gone in 3 to 5 years. These organics will be replaced with a mineralized soil that has no organics in it, soil life is dying and water drainage is getting increasingly worse.

            Fruit trees were planted using a 50% (volume/volume) mixture of compost and raw desert soil. All fruit trees were staked the first growing season and pruned in the same fashion after planting. No fertilizer was applied except for phosphorus to the bottom of the planting hole at the time of planting.

            All fruit trees were watered the same using a 3 foot wide basin, 4 inches deep, filled with water. All trees were staked and surrounded by chicken wire to prevent rabbit damage.

Irrigation basins around fruit trees, if they are not being watered by drip irrigation, should be level, large enough to be half the size of their canopy and 3 to 4 inches deep. Irrigation basins must get larger as the tree gets larger to provide enough water to the tree.

            Half of the fruit trees were randomly mulched with a 4 to 6 inch layer of wood chips made from local trees removed from home landscapes locally by First Choice Tree Service. The other half of the fruit trees were surrounded by bare soil.

            Mulch was kept away from the tree trunks a distance of 12 inches. The mulch was made from a variety of local trees not including palm and mesquite.

Mulch like this with a variety of different types of wood, not 100% bark, makes a great addition to the surface of desert soils. Don't let this valuable commodity go to waste in our landfills.

            At the end of the first growing season, fruit trees surrounded by surface mulch were more than twice the size than those without surface mulch.

            This mulch is available for free on a serve your own basis from the University Orchard in North Las Vegas and made available to the Orchard by First Choice Tree Service. If you want a large volume delivered, contact First Choice Tree Service.