Greenhouses by June Morgan
The growing of plants in a covered house or artificial conditions is essentially a northern hemisphere phenomenon, and the first attempts go back to early classical times. At first were only simple unheated orangeries for protecting citrus fruit, but by the 17th century these had reached a fair degree of perfection. The unheated orangeries were followed by conservatories for protecting tender plants and became the greenhouses of today.
The three major types of greenhouses are the lean-to, the attached and the freestanding. The lean-to is usually small, and opening from an existing house window. Its major drawbacks are a lack of space and a tendency to heat up and cool off more rapidly than desired. The attached greenhouse is an extension of one’s home and often incorporates a living or seating area into the larger space. It provides more control over humidity and ventilation. The freestanding greenhouse is unattached on all four sides. More expensive to construct, it offers maximum light and the best control. In very cold weather it might be a challenge to get out to a freestanding structure, while having it attached can utilize the house electricity and water systems.
The gardener’s first decisions are what he wants his greenhouse to do and where he wants to do it. Will there be raised beds using the ground soil and/or containers on the floor and shelves? Will it be primarily a place to winter plants, start seedlings, raise food, or, at different times, all of these tasks? Since just one greenhouse cannot do everything at once, scheduling according to the seasons and needs of the plants is at least, a partial answer.
Three main types of greenhouse environments are cool, warm, and tropical. The cool season is from mid October to mid March. Then, leafy lettuce and roots thrive between freezing and 50 degrees. This is the time to start seeds. If too early, the seedlings will suffer from transplant shock, be root bound and stunted. If too late, there will not be enough roots to handle the transplant stress. Both warming and grow lights can be raised and lowered to augment the light and temperature by suspending them from the ceiling with chains and S hooks. Some seeds, like peppers, require extra heat in order to sprout, so thermometers and humidistats are useful tools.
As the temperature warms, the greenhouse can be a resting place for tender plants waiting for the last frost date before planting outside. Before transplanting, pick off the blooms and harden plants gradually by giving them just enough water and fertilizer to keep them going. When the really hot weather arrives, consider putting most things outside in a protected place with watering easily available unless the energy bills are of little matter. Fans and shading help, but most people abandon the greenhouse until later.
Fall is the time to bring in small healthy annuals and non -hardy citrus, plumeria, etc. for overwintering, being careful not to bring in pests. The greenhouse should have been washed down and cleaned of extraneous material such as spider webs and made ready for the new cycle of planting.
Excellent books that go into much more detail about building, measuring light, plant choices, etc. include GREENHOUSE GARDENER’S COMPANION by Shane Smith, THE COMPLETE BOOK OF THE GREENHOUSE by Ian G. Walls, and ORTHO’S ALL ABOUT GREENHOUSES.
The gardener should not think it mandatory to fill the greenhouse with everything possible or hard to maintain exotics. It is there for gardeners’ enjoyment on their terms.