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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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May 20

Cold Frames

Posted on May 20, 2016 at 9:19 AM by Ann Vallee

by Charlene Burgi

Tomatoes protected by water walls
 Tomatoes protected by water walls
After a mini heat wave this week in Marin, cooler weather is in the forecast—just another example of spring's fickleness.

These unstable spring weather conditions and cool nighttime temperatures can play havoc on starting a vegetable garden. Create a stable environment for your tender seedlings by protecting them.

Tomato plants manage the varied cold temperatures better when planted with water walls surrounding them. Water walls can be purchased at your local nursery. For other tender seedlings, keep them in cold frames until the temperatures stabilize.

Cold frame
Cold frame with top removed. This one is built on casters so it is easy to move.
Cold frames are easily constructed by placing an old window pane or rigid sheet of plastic on top of a four-sided wooden box placed toward the sunlight. If it is warm enough during the day, raise the window for air circulation, then close the window during the evening hours. If the temperatures remain frigid, keep the window closed to maintain the warm collected solar air inside.

You can also make a simple hoop house for raised planter beds by purchasing a length of chicken wire. Arc the wire over the raised bed and secure it to the wooden sides of the bed with U-shaped nails. Cover the wire and the open ends with plastic sheeting material. 

The benefit of this method is that, when the sheeting is removed, your plants are still protected from rabbits and deer (be sure to enclose the ends of the hoop with wire or secured material).  And the chicken wire openings are large enough to allow bees to come in to pollinate!

If you employ cold frames, take note that they can dry out the plants faster. Be certain to watch the moisture level of these protected plants.


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