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Except where cold comes
early and is accompanied by high winds, fall is the best season
for planting trees and shrubs. A long autumn, plus fall rains
spur rapid and abundant production of new roots because the
plant does not need to put energy into making and maintaining
new, above-ground growth.
Most references say its
safe to plant woody plants until the ground starts to freeze. A
more precise safe-date determination was made by researchers
from Cornell University.
Plantings were made on the
21st of each month from August through November. Evaluation of
the plants during spring and summer of the following two-years
showed that those planted as late as October 21 had only
slightly more winter injury than earlier plantings, but those
planted on November 21 suffered significant to considerable
winter injury, with reduced size and quality, still evident
two-years later.
The November plantings were found to have developed virtually no
new roots, due to the soil temperature a
6-inches depth having
fallen below 40-degrees at the time of planting.
Thus the last safe planting date the researchers concluded, is
about 4-weeks before soil temperatures in
the root zone falls to
40-degrees, at which time root formation is halted.
Maryland Soil
Temperatures
The Belstville Agricultural
Research Center has a 24-hour/7-Days per week soil temperature
reader off of Powder Mill Road and six years worth of data. The
soil temperature reader covers 2, 4, 8, 20 and 40-inches in
depth.
I tried to get mean monthly temperatures for 4 and 8-inches,
during September, October, November and December and then
extrapolate when we hit the 40-degree mark on average, and then
backtrack 30-days.
I can't interpret the data. Maybe you can?
I've always
understood that late September thru the end of October was
'prime time' for hardwood
planting, and never planting past
Thanksgiving, then being better to wait until the
March/April planting season, especially for evergreens.
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