Northern Greenhouse

Northern Greenhouse

Bob's Projects & Ideas

Water Trench In My Rebar Greenhouse

Drastically Reduce Watering!

Where the poly cover meets the soil on each side I have dug a shallow trench. The poly is laid over that, and anchored with boards and blocks. The rain then runs down the side into the trench. Another poly-lined trench from inside the greenhouse intersects this. A hole is punched into the first poly lined trench coming from the outside, which lies over the bisecting inside trench and water is thus quickly channeled into the greenhouse. Down the center of the greenhouse I've dug an 18-inch deep 3 foot wide sunken pathway. This trench pathway is lined with woven poly and secured at the top with nails poked into the soil. Rain enters this trench from the poly-lined trench going to the outside. Boards are then laid across the sunken pathway at intervals to permit walking along it. What happens is amazing!

All those thousands of pounds of water act as a giant thermal mass absorbing excess heat in the day and warming the plants at night. I water the plants by simply scooping water from the trench with buckets and drenching the plants along the sides or in the metal barrels that line the pathway. But even though the temperatures are frequently in the nineties, I do not water often, sometimes as long as 4 weeks apart. Heavy mulching keeps the soil moist.


Two reasons. First, the water trough produces a steamy humidity, which envelops the plants like a fog. This prevents wilting even if it hits 100 degrees F. The leaves bathed in this humidity do not need much watering. Secondly, I heavily mulch all exposed soil. This lessens evaporation and also practically eliminates weeding. Tomatoes, melons and cucumbers seem to enjoy the humidity. Incidentally high humidity could spread mildew and fungus, especially in humid climates. In that case cover the water trench with a layer of poly beneath the boards. I've noticed the cabbage family like drier air.

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