The Cheap and Easy Greenhouse: No Heating Required
In my last post, I discussed Peter Henderson’s 1875 greenhouse/hothouse plans for the wealthy. But Henderson deserves credit: he didn’t just write for the rich, he wanted people of every income to have a chance to grow a plentitude of houseplants and exotics.
After he’s exhausted himself on the subject of the Ideal Greenhouse, his Gardening for Pleasure continues with ideas for attached greenhouses and greenhouse-pits that need no artificial heating to hold the plants you would keep in a cool greenhouse. It’s advice that modern half-hardy and tender plant growers might use, since rising fuel prices make heating a greenhouse an increasingly expensive proposition.
The attached-greenhouse method only works in areas with relatively mild winters; Henderson wrote from Jersey City Heights, where it freezes and snows, but not inordinately. (New Jersey, whose car licenses still read “Garden State”, was at that time a huge market-garden area that served the massive population of New York City.) A small greenhouse attached to a heated building, properly constructed, says Henderson, will keep plants going in places where the temperature doesn’t fall below 25 degrees F (-4 C). It needs to be tightly glazed, and shielded from the north and north-west (if you’re below the equator, change the directions accordingly).
The pit greenhouse (which seems to be a kind of glorified sunken cold frame) is even better, Henderson says. “This is formed by excavating the soil to the depth of from 18 inches (45.7 cm) to 36 inches (91.4 cm), according to the size of the plants it is intended to contain. A convenient width is 6 feet (1.83 meters)…and of such length as may be desired.” He cautions that the ground must be dry enough that water won’t seep into the pit, and advises walling the sides of the pit 4 (10.2 cm) to 8 inches (20.3 cam) high with brick or planks.
“The back wall should be raised about eighteen inches (45.7 cm), and the front six inches (15.2 cm) above the surface, in order to give the nursery slope to receive the sun’s rays and to shed the water.” If glass is laid on top, and light shutters or half-inch boards laid on top of the glass every evening, “it may be used to keep all the hardier class of greenhouse plants, even in localities where the thermometer falls to zero (-18 C). ”
While plants in such cool greenhouses won’t thrive lustily, they will be ready to go at the first sign of warm weather. That way, you wouldn’t have to grow out tender or half-hardy plants from small slips every year, or buy them new. If I bestirred myself to make such a pit-greenhouse, I could have the large collection of scented and flowering geraniums I’ve fantasized about, or keep beautiful brugmansias over winter reliably, and flower them before frost. I wouldn’t have to beg friends to babysit my houseplants when I go away in winter, either. (I don’t have central heating, so if temperatures fall below freezing, my houseplants turn to mush.)
Older technology has a lot to teach us. While we may not have the stay-at-home lifestyles or cheap help of past eras, many of these antique ideas make better sense than energy-eating options we are offered today.