Last year's Zone 5 plants didn't read the new
If your landscape is populated with plants chosen because
they had proved hardy to zone 5 temperatures (-10F to -20F average
minimum temperature), it doesn't matter that your neighborhood is
now included in a warmer zone 6 on the redrawn USDA maps. Your
plants can still handle that cold.
With respect to the USDA weather experts, we remain
skeptical of the new zoning and will keep selecting plants as we
did before. We will keep choosing -20F plants because we have seen
-20F in our garden in our lifetime.
Our skepticism rests fairly simply on the difference
between the hardiness zone map's revision interval and plant
longevity. The hardiness zone map was revised based on something
more than 20 years of data. Sounds like a lot except the trees and
shrubs we plant can live a century or more and although we won't
see all of that we certainly love to imagine them living on into
venerable old age and the future gardeners who may enjoy
Cold? Snow worry!
As for this recent cold, we don't think it caused much
trouble to our garden. We had wonderful,
early, deep snow cover with an extra blanket laid on just
before the deepest cold descended. The soil was not even frozen
below the snow -- check it now, you'll see. So the crowns of
perennials and the most tender parts of woody plants -- the
bases of trunks and the roots -- were cozy at 32F or above and well
protected from wind. (This, by the way, may be a mixed blessing.
There are many people rooting for the cold to kill
invasive species and that wish wouldn't be fulfilled in cozy
We're not surprised that a soil probe won't penetrate.
Even a very thin layer of ice can stop a blade, and there may be an
inch or more of frozen soil capping the ground, especially in
places where the sun doesn't reach. However, that soil is not super
cold though, not cold enough to hurt plants. It can hold at 32°F,
not becoming super chilled unless it's directly exposed to even
colde air -- not going to happen with a snow buffer between!
Rabbits, mice another matter
The snow may buffer something we don't want, too. We may
see extra trouble from rodents and rabbits. It may be happening now
but we won't see it until spring unless we go digging now. That is,
all that snow provides protection (from hawks and owls) for
trunk-gnawing rodents, and elevation for hungry rabbits. Poor
plants, poor gardeners, we slip one punch only to meet another --
it's always something!
And then, the "garage plants" - a 3rd different
Argh! We should have thought about this when we first
heard the weather forecast: The marginally hardy plants we store in
our unheated garage over winter. They survive out-of-zone because
they have a few degrees of extra protection. This year the zone 6
rosemary (Rosmarinus officinalis) was there, rather
than in the house. Sad, when something we've had for 20+ years
may be a goner. Too late now!
Weather and work
Aren't weather stations fun? Now you can become a weather
reporting station, too. I love to check the weather (we like weather
underground's format) and see exactly where the reported
We are indeed staying warm - thanks for your concern. We
did stay indoors when the mercury dropped to -17F and we didn't
stay out long when it was -10F and windy. However, with thermal
underwear, warm pants and shirt, sweatshirt, vest and coat plus
boots and insulated gloves, we actually got sweaty while working.
Things we had to do: Shovel snow, lift up overburdened branches so
snow could slide off, clear deep snow from the bird feeding areas,
and keep an air vent in our pond.