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SMALL TREES GROW FASTER THAN LARGE FOLLOWING TRANSPLANTING
Ever wonder why large transplanted trees don't seem to grow very fast during the first years following transplanting?
The reason, according to Dr. Gary Watson of the Morton Arboretum, is that as much as 98% of a tree's root system can be left behind when it is dug out of the ground. When transplanted, often less than 5% of the absorbing roots are moved with the tree, Watson says.
While the percentages hold for both large and small trees, larger trees lose a much greater mass and lateral spread of roots than smaller trees. Because roots of large and small trees grow at the same rate (roughly 18 inches a year), it takes the large tree several years longer to regain the size of its original root system. Thus, Watson explains, large trees often experience a long period of slow top growth after replanting.
A tree with a 4-inch diameter trunk will require, according to Watson, five years to regain the size of its original root system, which was 18 feet in diameter. A 10-inch tree with a 45-foot diameter root system will need 13 years to recover!
Watson says the root system of the smaller tree will have become nearly as large as that of the 10-inch tree after this 13-year period. Therefore, he concludes, because the smaller tree has had several years of vigorous growth while the larger tree was under stress, the smaller tree actually may overtake the large tree in growth by the time the larger tree had restored its root/shoot balance!
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Why are majestic bur and white oaks dying? I've raised the question before in this column, and received many phone calls about the problem.
I recently read the best explanation yet for a possible cause. An article in the DNR's Forest Disease Newsletter reported that many oaks in recent years have been turning yellow during the second half of the summer. Yellow foliage is a sign that the chlorophyll molecule, so critical in photosynthesis, is breaking down. When photosynthesis stops, the tree must begin living on stored reserves.
Oaks - all trees, for that matter - need green leaves during all of July, August and early September. This is the time of year that oaks, having grown new leaves, shoots, acorns and wood for the year, begin to stash starch for future use. Trouble is, chlorotic (yellow) leaves don't photosynthesize. The sad fact is that these chlorotic trees are in trouble because they can't manufacture food.
To make matters worse, these weakened trees are susceptible to the two-lined chestnut borer, the bane of weakened oaks, which initially kills the very top branches and, eventually, the entire tree.
One condition common to many of these chlorotic trees is high soil pH (over 7.5). The article reported that several severely chlorotic trees have had a pH of 8.0 or greater!
Factors contributing to high pH include: leaf raking and removal, removal of grass clippings, sod liming, watering with city water, road salt, and residue from concrete foundations and driveways.
You can encourage a more favorable soil profile for trees by mulching grass clippings and fall leaves back into your lawn, never liming under trees, and mulching the soil around trees so that irrigated water filters down through the decaying organic material.
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PUTTING DOWN ROOTS:
A Delightful Blend of
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