From: hud@netcom.com (Hud Nordin)
Subject: Re: Cold frames
Date: Fri, 13 Aug 1993 19:56:18 GMT

"Charles R. Estabrooks" CRE@IMAGESYS.COM writes:
> As a bonsai newbie, please help me understand.  I have two junipers,
> which I have been told by an experienced bonsai hobbyist can be kept
> outside year round, and, indeed, need to be kept outdoors for their
> required dormant stage.

> My bonsai trees and I live in upstate New York, and we have fairly
> long, cold (weeks of sub-zero, sometimes) winters.  There is often
> snow on the ground, but not always.  Do I need to protect even the
> cold-climate bonsai plants like the Junipers, or is protection from
> wind dessication required only for certain bonsai varieties?

It depends on the variety, but if the stock was sold for landscape use
then it should be perfectly able to survive your winter. But, a bonsai
in a shallow pot needs a little more care than a similar plant in the
ground.  Its poor little roots are mere inches away from the air.

I understand that temperature variations are one of the big factors in
winter damage, and not just the cold. Weeks of sub-zero (Fahrenheit, I
presume) can be surrounded by time near, or--Horrors!--above,
freezing.  The plant with its roots in the ground, often covered by a
blanket of snow, doesn't see the changes like an unprotected bonsai
does. A "January thaw" can wake an unprotected bonsai out of dormancy,
to disastrous results when winter makes a comeback, while the plant in
the cold ground doesn't notice the heat wave.

So, one key is to provide some shelter to the bonsai. Coldframes are
often sunk into the ground, so that the surrounding earth moderates
the changing temperature, and, with glass, trap a quantity of air
around the bonsai, again to insulate them from the changes. Especially
when the temperature in the coldframe might hover around freezing due
to the greenhouse effect, people actively monitor conditions inside
the coldframe and try to keep them fairly constant, e.g. by opening it
up a little on warm days.

I'm the guy who just buried my pots in the ground for winter and
covered the trees with snow. This worked in Minnesota because the
frigid temperatures ensured the blanket of snow stayed in place pretty
much all winter. I never had any problem with the native species or
those sold for landscape purposes. In slightly warmer climates,
"artifical snow" in the form of a coldframe, or an enclosed porch, are
usually necessary.

Brr. All this talk of winter!

How are you folks on the other side of the equator doing? In
California, when it is one month before spring, I can see dormancy
begin to break, and it is an exciting (and busy) time. With spring
approaching, how's it going where you are?
-- 
Hud Nordin
Cybernetic Arts                 hud@netcom.com
Post Office Box 2066            Telephone: 408.248.0377
Sunnyvale, California 94087     Facsimile: 408.248.0416