Green thoughts: When drier means tougher Baby, it's cold
outside! While we huddle up to the fireplace or pay the oil
delivery man for our comfort, trees and shrubs just stand out
there and grin. How do water-filled woody plants survive
freezing, especially when temperatures fall well south of zero?
Let's de-mystify this rather complex process. Cold hardiness
depends upon not just how cold the air turns, but also on
rainfall, light intensity, day length, soil fertility, previous
high temperatures, and the consistency of temperatures. The
shrinking light and dropping temperatures which accompany autumn
are the most crucial of these influences which naturally trigger
plants to develop cold tolerance. The longer a plant is exposed
to these changes, the hardier it gets. Scientists call this
"acclimation," while gardeners know it as "hardening off." If
frigid temperatures occur before proper acclimation, plant
damage may result. For example, August's English ivy plant may
die if exposed to 25 degrees F, while it ma