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Fall is in
the Air
Aspens & Chokecherries |
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The seasonal aspect of life in
the geographic regions north (and south) of the
tropics is so much an integral part of our life that
we tend to not even think about it—except perhaps
for those one or two weeks where the change of
seasons is relatively obvious. Like the first
frost of autumn, the first snowfall, the first
spring rain, and the first truly hot day of
summer. These tend to be the jarring events that
hit us over the head every three months or so to
remind us of the seasonal nature of our lives.
Seasonal growth and dormancy
are the adaptation of plants and animals alike to
the changes in weather produced by the joint effect
of our planet’s tilted axis relative to our sun and
the planet’s annual orbit around the sun. While we
in the northern latitudes may assume that all plants
winter dormancy is an inherent aspect of plant life,
that simply isn’t so. Dormancy is merely an |
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Research has shown, however,
that trees and shrubs mostly just change the
composition of the fluids in their trunks and
branches over the winter so that it won’t freeze.
Think of it as though they made their own
anti-freeze each fall. And it also appears that
some of the moisture in the branches of woody plants
does freeze over the winter, but the adjacent
tissues are able to expand to accommodate the
freezing without being damaged. Still other
trees—the evergreens—even keep their leaves in the
winter. And there is some evidence that those
leaves continue to function as temperatures permit
through the fall, winter, and spring. Likely the
main reason that so many of the northern forests are
dominated by evergreens
The means of surviving winter temperatures makes a
big difference in the ability of each type of plant
to be able to compete for space within their |
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Herbs
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Wildflower Week
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August 31st
Tree Roots at the
Old Pen
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Recipe for Enjoying
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September 14th
On the Road to Casper
Coming Soon
A Prairie Garden Journal
Searchable Archives |
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Seasonal growth and dormancy are the adaptation of
plants and animals alike to the changes in weather
produced by the joint effect of our planet’s tilted
axis relative to our sun and the planet’s annual
orbit around the sun. While we in the northern
latitudes may assume that all plants winter dormancy
is an inherent aspect of plant life, that simply
isn’t so. Dormancy is merely an adaptation of some
plants to the annual fluctuations in temperature and
perhaps light volume attributable to the earth’s
orientation and movement relative to the sun. And
what a remarkable adaptation it is.
Some plants survive the adverse conditions of winter
by producing seeds which can survive the winter even
though the plants themselves die. This is the
adaptive mechanism of the plants that we call
“annuals”. Certain other plants survive winter by
pulling all of their growing resources back to the
more stable temperature environment of the upper
layers of the soil for the coldest seasons. We
call these plants perennials. They re-grow their
above ground stems and leaves each spring and
summer, but rather than keep the stems and leaves
alive through the cold of winter, they simply store
extra energy in their root system each growing
season to be able to form new stems and leaves at
the start of each growing season. We call these
plants “perennials”. Many of the planet’s grasses
fall into this category, although there are also
many “annual” grasses.
Trees and other “woody” plants
have evolved even more sophisticated means of
surviving the seasonal changes in the weather of
northern climates. They only re-grow and abandon
their leaves annually, because they have developed
the ability to “winterize” their stems—the trunks
and branches. Many still mistakenly believe that
hardy trees and shrubs pull all of their “sap” back
down into the ground each fall and store it in their
root systems over winter. |
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native ecosystems. Trees are
the clear winner in the competitive race for space
in their native ecosystems. The ability to have
their trunks and branches survive the winter allows
them to grow much taller than the perennials and
annuals which must begin growing from the ground
each spring. So it’s only adequate supplies of
water and soil nutrients that are the primary
factors which limit tree and shrub growth, while
space, time, and quantity of sunlight are the
factors which limit the growth of perennials and
annuals.
The process which we now see
being played out in our gardens and landscapes is
truly remarkable. The ability of plants to grow
seasonally and then to “shut down” through the
inhospitable winter may not be quite as
awe-inspiring as the transformation of a caterpillar
into a butterfly, but it is nonetheless one of the
true wonders of the natural world. Perhaps it is
no accident that this transformation of the
landscape is also characterized by dramatic displays
of colorful leaves, stems, seeds, and fruit. Enjoy
the new season!
Nannyberry Viburnum |