Steady Cold Temperatures
helps that this winter has stayed seasonably cold pretty much since
it started, rather than big temperature swings that have marked
Pittsburgh winters in recent years.
Plants are better off when it gets cold and stays
cold through the winter, and attain their maximum cold hardiness in
January and early February. While humans enjoy those warm spells in
winter, they can cause plants to lose some of their cold hardiness,
which makes them more susceptible to severe damage from
exceptionally cold weather.
Soil drainage is another important factor.
Well-drained soil that allows water to drain away from the roots and
crowns of plants improves their winter survival greatly. Conversely,
poorly drained soil that allows water to pool around the roots and
crowns of plants is a recipe for disaster. Do not assume that sloped
sites have good drainage. Pockets of deep clay, drainage from
natural springs, and runoff from building sites can cause poor
drainage even on slopes. It can be frustrating, because an area can
differ in drainage patterns practically from foot to foot.
Cultural practices also have a bearing on a plant’s
winter hardiness. Plants that receive optimal moisture and fertility
and protection from insect and/or disease problems during the
growing season are healthier and will fare better through the
winter. Plants suffering from drought stress, nutrient deficiencies
or insect and/or disease problems may not survive the added stress
of our extra-cold winter.
Proper management practices help plants harden off
for the winter. Avoid pruning and fertilizing trees and shrubs in
late summer and early fall. These practices stimulate succulent
growth that may not harden off before cold weather arrives. Do not
fertilize perennial herbaceous plants in late summer and early fall
for the same reason.
serves as an
Insulation Blanket for Plants
It may seem counterintuitive, but good snow cover is
great insulator. Unfortunately, we had unseasonably warm weather
just before the first polar vortex descended on us that resulted in
very little snow cover, at least in and near Pittsburgh. We did have
more snow for the polar vortex’s second visit, but the cold stayed
with us much longer. The impact of lingering cold can range from
dead flower buds on plants such as forsythia and bigleaf hydrangea,
to plants that die above the snow line, but are fine where they were
USDA Plant Hardiness Zone Map
Finally, when buying woody ornamentals, make sure
that seed-grown plants originate in the same zone or a colder zone.
Seed from plants grown in warmer climates may produce individuals
that are unable to overwinter in colder climates, even though the
species is considered hardy. Red maple (Acer rubrum) is a great
example because it ranges from Quebec to Florida. Offspring of
plants growing in Quebec are unlikely to tolerate the heat and
humidity of Florida, and offspring of plants growing Florida are
unlikely to survive the winter (especially this winter!) in Quebec.
Storing Seeds from your Garden
Winter garden beauty