It took my wife and me several years to learn that not everything will grow in a cool greenhouse. Hopefully, a gloriosa tuber, African violets, gloxinia seedlings, and Christmas poinsettias rushed to our greenhouse and just sat there from October to March, waiting for spring weather.
We finally realized that they needed warmth. After experimenting, we found that our 50° degree Fahrenheit greenhouses would give us beauty and satisfaction only if we learned what would grow in them.
What Temperature Plants Need
After a few winters of trying everything at once, we discovered valuable information on the temperatures plants need in books, garden magazines, and greenhouse bulletins. So, we began to be selective.
The poinsettias and the African violets went out, although I had to dispose of some of them when my wife wasn’t looking. Instead, we started varieties of geraniums and begonias.
Many plants, valued for their ornamental foliage rather than their flowers, grew well at 50° degrees Fahrenheit. We added unusual things like Billbergia nutans to our liable collection, and they bloomed under the conditions we provide.
To our surprise, we found that some cacti could be made to flower without difficulty. We have heard the Christmas cactus needs a high temperature, but ours do very well at 50° degrees Fahrenheit and are fully bloomed from Christmas to March.
We follow with interest the unpredictable flowering habits of the epiphyllums, almost ugly until the salmon and pink blossoms, 3” inches or more in diameter, open.
Great Pelargonium Variety For Greenhouse
But we feel that for the cool greenhouse, there is nothing like the great pelargonium family for variety and cultural ease. Its members come in white, all shades of pink and red, to the bright vermilion we all knew on grandmother’s window sill.
There are dwarfs, ivy types, and scented-leaved varieties like the old-fashioned rose geranium. Some even took little pansies. But we vote enthusiastically for the Lady Washington stately aristocrats in resplendent shades, beautifully formed and marked.
They need no more care than other geraniums except an alert watch for the white fly that likes their foliage. A fumigant does short work of these.
Books indicate that Lady Washingtons should have temperatures somewhat higher than we provide, but they do very well for us, blooming profusely from March through summer.
Heating System
How do we maintain our 50° heat? We had some second-hand radiators installed in our four-section greenhouse and connected them to the house’s hot-water heating system.
The greenhouse is some distance from the house, so this involved a trench, thermal insulation, and a motor-driven circulator.
An aquastat controls water temperature, and the circulator is operated with automatic thermostatic control.
The water temperature cannot get much above 140° degrees Fahrenheit. With everything working, the greenhouse stays at 50° degrees Fahrenheit as long as the outside temperature does not drop below 10° degrees Fahrenheit.
Greenhouse Maintenance
Greenhouse maintenance is chiefly cleaning and painting – something you can avoid entirely with the new aluminum models.
One year, we hired a man to scrape the old paint and apply two new coats – at a cost above $350. We try to do the cleaning and painting ourselves, but it is never finished on schedule.
We will move everything out of the greenhouse by the end of May. We leave many plants, including Callas and camellias, in their pots to rest in the shade. Others we set on walls and in corners for summer decoration.
The geraniums and begonias are transplanted into window boxes and open-ground beds. Plants like lantanas and fuchsias are brought into the greenhouse so they won’t freeze in winter.
The move back indoors takes place before the first frost and is usually finished before October 15.
There are always treasured plants in the gardens which have not yet bloomed or are still blooming furiously in October to take up and install in the greenhouse just to see what they will do.
A Few Flowers Pop Out by Christmas
Pink and yellow oxalis, impatiens, some begonias, and geraniums. By the first of March, everything goes to town together. Nasturtiums, sown in November, start flowering early in April.
Too many different kinds of plants require too much work, so we intend to specialize in pelargoniums.
If I have my way – I sometimes do – we’ll have only Lady Washingtons. And, boy, will it be magnificent – even if the temperature is only 50° degrees Fahrenheit.
44659 by Charles H. Roe