posted 6 years ago
I have a little greenhouse, entirely passive. Last year we had tomatoes into the middle of December. This year I have two tomato plants, two peppers and two sweet potatoes. It's only the 2nd full summer with the greenhouse, so I'm still experimenting.
It depends on a lot of things--I assume you're trying to bring the temperature up at night. Is the greenhouse insulated? Any thermal mass? Are you looking for year-round growing, or just extending the growing season? Are the tomatoes for sale, or for your use? Are they in the ground (my preference) or in hydroponics, or in wicking beds? What kind of temperatures are you trying to mitigate?
If you have space, I'd say go for the compost heap (or pit). I didn't have room for that in my greenhouse. The compost won't stop radiating during the day, so you'll need a way to get rid of (or store) the excess heat. I created a waterwall and put in big water barrels for thermal mass. Straw bales are another option, or layers of insulation.
New location. Zone 6b, acid soil, 30+ inches of water per year.
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