Gravel bed grown trees

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Variegated dogwood growing in pea gravel the first year after planting.

The most common tree failures we see are related to root problems and poor planting of container grown trees. The typical failure is from 3-10 years after planting due to unseen problems in the root ball and improper planting. Sadly we see containerized or balled and burlapped (B&B) trees planted by the “drop and plop” method–drop the container and plop the root ball into hole, which is usually dug incorrectly. Without visual inspection of the root system problems go unnoticed. Some nursery tags encourage “drop and plop” planting with warnings to not disturb the roots. The problem is the health of root system is a mystery, and the future of the plant is also a mystery.
So are there better methods?
There certainly are, and one is found in our “Root Washing” blog. Root washing is a technique that exposes roots for proper transplanting as explained in the blog and another method is to grow trees in a soil-less media, like pea gravel.
To demonstrate the advantages we are growing trees in pea gravel at our facility in Olympia. The intent is to show how quickly roots grow and to encourage correct transplanting techniques. We’ve been coached by Dr. Chris Starbuck, MSU horticulture professor who has grown trees in pea gravel for transplant on the Missouri State campus for many years. The resulting root growth was pretty amazing as the picture below demonstrates.

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This tree was field dug and planted in pea gravel with  9″of roots on either side of the stem. With roots spread out they would easily measure 4′ across during the second year in the pea gravel bed . The tree weighs a just few pounds without the soil.

Plant anytime, even in full leaf or bloom.
Gravel bed trees and root washed trees can be planted anytime of the year as long as irrigation is provided.

No soil = no heavy root ball.
Back injuries top the list of landscape injuries but a 3-4” caliper gravel bed tree can easily be carried by one         person, where a B&B tree could weigh hundreds of pounds requiring more personnel and equipment to move.

Transportation is easier because trees can be placed much closer together.

Without soil there is no interface problems for new root growth.
If B&B or potted trees are planted with nursery soil intact it creates an interface between the nursery soil and the planting soil. New roots may not “choose” to grow into unfamiliar soil with different biological components and stay in the nursery soil creating circling roots that can lead stem girdling (strangling) roots which can kill the tree.

Nursery soil is typically heavy and will retain moisture but if the soil dries roots will die.
We’ve seen countless tree failures where root ball irrigation wasn’t provided at planting. Gravel bed tree roots have immediate contact with moisture at planting and with proper irrigation don’t go through the stress that containerized trees do and continue to grow normally.

Planting depth can be correctly determined when roots are visible.
Containerized trees are often planted too deep. The root system of a gravel bed grown tree can be viewed and the tree planted correctly, with root collar or root flare visible above the finished grade. The planting hole (shallow, saucer shaped) can be dug at the right depth so the root plate (where the roots turn away from the stem or trunk) will lie on firm soil, eliminating the problem of sinking (subsidence) often found when heavy root balls are planted in loose soil.
With the roots visible, planting with a mudding technique where soil and water are placed in and around every root ensures good stabilization and staking is usually unnecessary.

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We have about 50 gravel bed trees for sale now at wholesale prices. Please call for current pricing and species list. We will be planting different species next spring and those should be available next fall. We hope this method catches on and someone in the Northwest starts growing a significant number of trees in pea gravel.

The Gravel Bed Project Slide Show