Simple hotframe
by Alan Detwiler April 12, 2013

Make a simple hotframe: 200130412

If you start your own cabbage, cauliflower, or brussel sprout plants from seed and do not have a greenhouse or hotbed, you may have had trouble with the seedlings growing tall and spindly from lack of sufficient light. Here in zone 6, placing early spring seedlings near a south facing window just does not give the optimum amount of light needed for sturdy growth. It's often too cloudy and there is not as much light in any indoors location as there is outdoors.

Last year I configured a simple hothouse with just a frame of window glass and a few pieces of brick. The window glass was leaned at a 45 degree angle against the outside of a south facing wall of my house. The brick was used to close off the ends of the hothouse. That arrangement exposes the seedling to somewhat more light than an indoors location near a south facing window. Having the seedlings also has the problem of too warm a temperature during cloudy weather. Heated indoor space is too warm for low light conditions. You don't want the high rate of growth and spindly structure that the combination of warmth and low light produces. The simple hothouse with the ends open usually provides cool temperature during cloudy weather.

During sunny cold weather the ends can be closed with the brick to boost seedling growth. If frost is forecast, a blanket can be placed over the glass to protect the seedlings.

You do have to be careful when the weather is sunny. With ends closed off, temperature within the hothouse can be 40 degrees F. or more above ambient. That can dry or cook seedlings quickly. Make sure the ends are wide open when temperatures are above 50 degrees and the weather is sunny.

Using this simple hothouse is easier and produces better growth than having the plants indoors and/or moving them back and forth between indoors and outdoors every time the weather dictates. It is especially good for the cabbage member plants as they can be left outdoors during light frost if protected with a blanket. The brassicas seem to do better than heat loving plants like tomato and peppers in the sometimes chilly weather of spring..

Cauliflower seeds being sprouted in almond milk containers behind glass in early spring 2012. Thermometer monitors temperatures. Opennings at ends of hothouse are widened or narrowed to regulate temperature.
three 2X6s form a protected space

Best wishes,
Contributed by Alan Detwiler. Bio at

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