PLANT HEALTH CARE
Watered trees vs. not watered on same street.
In Minnesota, where I live, we are having an incredibly wet season
this year.We have had more days in June with rain than days without.
We have not had two weekends in a row without rain since the first
weekend of March, which is only because there was still snow coming
down then.The windows where I am writing today are still dripping
from last night's thunderstorm, so it begs the question — why are we
talking about drought? Clearly, it's raining, so the drought is over, right?
Well, maybe, but drought isn't a matter of it raining for a few weeks in
the spring or not. Drought is a long-term climate issue, one that most of
the United States is in the seventh or eighth year of, and it is taking its
toll on the plants.
Last year,in fact,was one of the most stressful years for plants on record.
In the northern parts of the country, folks were treated to a gloriously
warm and early spring — up to six weeks ahead of schedule in many
places.The trees and plants came out of dormancy to an environment
where water and sunlight were in abundance,and they responded accordingly.They dug into their reserves to put out flushes of growth and created
large vessel elements to transport the available water quickly.All was well.
Then someone turned off the tap.
12 Arbor Age / July/August 2013
By all accounts, the summer of 2012 was a historic drought. In fact,
according to a recent report from the National Climatic Data Center, it
was the largest drought in nearly 50 years, with 54.6 percent of the land
in the lower 48 states in drought conditions by the June. Measured by
an algorithm called the "Palmer Drought Severity Index," last year's
drought was the sixth worst drought since 1895 in terms of percentaffected land.To put this into perspective, the drought of 2012 edges the
1936 drought, and is slightly behind the 1934 drought that make up the
Dust Bowl era. In the 1930s, the droughts began in the spring so the
plants woke up to dry conditions and were able to plan accordingly.Thus,
in terms of the drought resulting in plant stress, 2012 was perhaps the
worst year ever recorded.
Even school children know that plants need water, but what are
they using that water for? Like most living things, plants are mostly
water; in fact, up to 90 percent of their mass is comprised of water. Not
only does water provide the turgid pressure that keeps plants rigid, it
is their primary means of temperature control. Nearly 95 percent of
the water a plant takes up is transpired to keep the plant cool. Plants
also use water for osmosis, chemical movement and photosynthesis.
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