By Nina Bassuk and Michelle Buckstrup
Ithaca, NY (2003)- Whether from a nursery field to the city tree lawn or just from one place in your yard to another, it’s the roots that suffer when trees are transplanted. Consider this: Shade tree roots are found primarily in the top 12 inches of soil. Tiny absorbing roots, responsible for most of the tree’s intake of water and nutrients, are in the top several inches of soil. Not only do roots grow horizontally beyond the dripline, but there is often a higher percentage of them beyond the dripline than within it. An unbelievable 90% of tree roots are routinely left behind in the nursery at the time of harvest. The fine absorbing roots that are harvested are easily broken off, damaged and desiccated. Water stress, resulting in part from the tremendous reduction in root mass, is the main reason transplanted trees fail. Bare root method planting could be the answer to this problem.
The three main arguments for bare root plantings are:
1. You can plant more trees more cheaply. Bare root trees are one-third to one-half less expensive than B&B trees. Because they are so much lighter and many more can fit on the bed of a truck, they are cheaper to ship. Planting a bare root tree costs virtually nothing when done by volunteers with shovels. The cost of planting a B&B tree, by contrast, is markedly higher because the sheer weight of the ball requires machinery and machinery operators to load the tree, unload it, and to get it in the ground.
2. You will take more roots along. A simple study was done at Cornell to compare the amount of roots in a B&B ball with the root mass on a bare root harvested tree of the same size and species. The bare root trees had 200% more roots. The reason for this? The harvesting machinery for bare root trees digs a much larger root system than the tree spade used for B&B digging.
3. You’ll avoid the deadly planting-too-deep syndrome. Frequently when a newly transplanted B&B tree dies, it is because it was planted too deep. When the fine absorbing roots are buried too far down, they can’t access oxygen and the tree suffocates. Trees should be planted so that their root flare begins just at the soil line. With B&B trees, the soil may be mounded on the trunk, making it difficult to see the buried root flare. On the other hand, the root flare of bare root trees is obvious and the proper planting depth easy to determine.
Need more persuasion? When you plant bare root you can spot girdling roots and remove them before you plant; with B&B trees girdled roots can be buried. With bare root trees you won’t rob nurseries of their valuable field soil and there is no ball of nursery soil meeting the city soil with potential “interface” problems in terms of water movement.
For municipalities with limited tree budgets, the low cost of the bare root method is the most critical factor. With a budget of $500, volunteers can plant ten trees a year.
The Bare Root Method
Urban Horticulture Institute