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Heat From Water

Wall-o-waters work to add early-season heat to vegetables.  They collect warmth during the day from the sun, and then release it at night to keep plants warmer.  They work well in my experience.

But wall-o-waters are an absolute pain to erect and to keep standing.  I heard a suggestion once to open them up around a five gallon bucket, fill them water, then carry them to the plants.  It helped, but I still don’t like them.

Using water to warm your vegetables can be done in other ways.  Gallon milk jugs can be used.  We buy laundry detergent in two-gallon plastic jugs, which are even taller for more heat and protection.  Spray-painting these jugs black will add to their heat holding ability.

To provide more heat, five gallon plastic buckets can be used, or 32-gallon garbage pails.  I set these next to a few of my tomato plants in my hoophouse.  After cold temperatures have killed the tomatoes that aren’t near the water, the tomato plants with this warmth next to them are still looking green and beautiful.

A metal container is quicker at transferring the sun’s heat into the water, but plastic will also work.  Both work best if they are painted black.  Or you can place a large black trash bag over the barrels.

Large water bags are sold for greenhouse use.  The merchant recommends at least three gallons of water for every square foot of greenhouse wall that admits sunlight.   That’s a lot of water.

Other heat absorbing materials are rocks or concrete blocks, but water has about two-three times the heat holding capacity.