This section is from the book "How To Make A Flower Garden", by Wilhelm Miller. Also available from Amazon: The Well-Tended Perennial Garden: Planting and Pruning Techniques.
A physician who takes time for a greenhouse gives some useful warnings.
To any lover of the garden the frost brings a feeling that the world in which he lives has lost half its beauty for him, and he anxiously awaits the time when the leaves once more begin to show their loveliness of green in the spring. If, however, he is the lucky possessor of "a small bit of glass," he has discounted the effect of the shock, and can continue to worship his favourite goddess in a small private shrine which is always conveniently at hand, and whose selected treasures seem much nearer and dearer than the lavish plenties of the summer garden. In this "winter garden" he can have a constant change of scene by shifting the various parts, and by bringing in the sleeping roots and bulbs to brighten the field whenever variety may be desired; and if he has been properly far-sighted there will be a "continuous performance," however limited the stage may be, until the returning heat of the summer renews the necessity of his attention being directed outside again.
These tender things are wholly dependent on you for their very existence.
To descend to more personal and practical details, my experience is that the man who has to run his own little greenhouse, and who has any sort of outside garden, would better not try to keep both going at full steam at the same time, unless he has an abundance of leisure time at his disposal. Somehow, too, there is not the attraction about the indoor growing of plants when everything is flourishing in the less-confined and healthier surroundings of the garden bed. Give your time to the greenhouse in the winter half, and to the outdoor life for the remainder of the year.
However, when one's "glass" is part of the house, and would look very forlorn if empty, a fair showing can be made with a few begonias, amaryllis, and foliage plants which do not love the exposure of the open, and which with sufficient shading and sprinkling will not suffer from the heat, as so many other greenhouse pets do. Some people use fancy-leaved caladiums to make a summer display indoors at a small cost in time and trouble. The umbrella plant (Cyperus alternifolius) is much used for this purpose. If there is a blank wall to be covered, Ficus pumila will be found excellent. It looks well both summer and winter, and requires little care.
My own little oasis opens directly out of the dining-room, and is heated by steam from the common furnace. I have deduced a few simple axioms for its successful operation.
Don't let green fly, mealy-bug, or scale go too long; smoke or spray when at all plentiful.
Don't have the place too hot; give plenty of air on every possible occasion.
Don't try to grow rare novelties; stick to robust, standard things that will not require coddling.
Don't try to grow palms and pansies under the same conditions; one or the other, if not both, will prove a failure. The things that do best with me are those that every florist sells as "house plants," and which are "the survival of the fittest."
Lastly, retire to your greenhouse when you have an attack of "the blues"; it will be the better for every one concerned. There is nothing like a greenhouse to keep one cheerful.