What's blooming
Rodger Whitlock (Thu, 23 Feb 2012 17:19:55 PST)

On 22 Feb 2012, at 18:18, Sujit Hart wrote:

Essentially a topless, bottomless wooden box covered with glass or transparent
or translucent plastic.

You wouldn't think so, but even such a simple affair can give a surprising
amount of protection from winter cold, thanks to the earth itself acting as a
source of heat - not high temperature heat, but heat nonetheless.

In addition, a coldframe offers protection from rain, important in winter-
rainfall climates like the Pacific Northwest.

Covered with a screen in warmer weather, a coldframe can also keep flying pests
at bay, notably narciussus flies.

Another benefit is that in summer a coldframe keeps the sun off the sides of
pots in it and prevents the soil in the pots from overheating. This is why many
nurseries corral their potted plants in areas surrouned with low walls of
masonry or wood.

You can make coldframes of any convenient material, but my experience is that
once you have a little experience with them, it's a good idea to draw up a
fixed design instead of cobbling them together from whatever is handy. This
mostly affects the cover: should it be old windows, or something made to
measure.

A bulb frame is a little different, usually referring to a masonry raised bed
containing pots plunged in sand, but invariably covered with barn cloches or
something similar that gives the plants some head room when they flower in
early spring (typically).

--
Rodger Whitlock
Victoria, British Columbia, Canada
Z. 7-8, cool Mediterranean climate