The temperature you maintain in your greenhouse plays an important part in plant growth. Greenhouses are classified as cold houses (unheated), cool houses (55 to 60 degrees at night), or warm houses (60 to 70 degrees at night). Whenever night temperatures are cited you should figure on a daytime requirement about 10 degrees higher. Each of these three classes of greenhouses is suitable for growing certain kinds of salable plants.

THE UNHEATED GREENHOUSE
If you live where outdoor night temperatures never dip below 32 degrees, you can run a cold (unheated) greenhouse the year round. Otherwise, you might find it profitable to operate a cold greenhouse until late fall, close it down during the cold¬est winter months, then resume operations in early spring. In such a house, you can make money on annuals, spring-flowering bulbs, and bedding plants by forcing or starting them in late February or early March. The cold greenhouse is also an excellent place for growing lettuce.

In summer, use the unheated greenhouse for tomatoes, seed¬ling perennials, or almost any plant that flowers in summer. In this type of greenhouse, winter-grown plants should be planted directly into the bench soil. Here they will withstand lower temperatures than if planted in pots. In the following lists are plants I have found profitable to grow under the various conditions specified.

FLOWERING PLANTS FOR THE UNHEATED GREENHOUSE
Spring
Anemone* Larkspur
Astilbe Lily-of-the-Valley
Carnation Narcissus*
Columbine Pansies
Crocus* Primrose
Cyclamen* Saxifraga
Daffodil* Scilla*
Forget-me-not Sedum
(Myosotis) Tulip*
Fritillaria* Viola
Hyacinth* Violet
Iris*
Summer
Begonia (Tuberous and Campanula
semperflorens) Canna*
Browallia Carnation
Calceolaria Celosia
(* Denotes plant usually grown from a bulb, corm, or tuber.)
Chrysanthemum Hibiscus
Crinum* Lobelia
Delphinium Oxalis *
Dutchman’s Pipe Petunia
(Aristolochia) Sedum
Flowering Tobacco Sweet Peas
(Nicotiana) Tigr idia *
Geranium Vallota*
(Pelargonium) Watsonia *
Autumn
Carnation Nerine*
Chrysanthemum Sternbergia*
Gladiolus* Sedum
Hosta* Sempervivum
Kniphofia* Zephryanthes
Lily*
Winter
Anemone* Iris alata
Crocus* Jasmine
Cyclamen neapolitanum* Saxifraga
Erica Solanum
Fatsia Viburnum
Freesia* Violets