Archive for December, 2005

Oil Heat

A forced-air oil heater is inexpensive. If you need heat in your greenhouse but a few times during the year, one of these fan-type heaters may be just the thing for you. The fan forces a brisk circulation of hot air through ducts running underneath plant benches. You can pipe the smoke out through a chimney or through pipes running under the bench and vented out one end of the greenhouse. This pipe surface gives off added heat and removes the necessity of a chimney stack.

Gas Heat

Many owners of profit-making greenhouses live in areas where natural gas is available. A natural gas unit is quite reasonable in cost. One low-priced heater is all-aluminum and about 12 inches in diameter and 22 inches high. A somewhat larger heater, 15 inches in diameter and 25 inches high, naturally is about double the price. This type of heater is set under the side benches so that heat goes out into the walk. It is vented and piped into the outer gutter or directly outdoors. These heaters are not recommended for use with fuels such as Butane or Propane.

Electric Heat

Where the cost of electric current is low, it might be feasible for you to heat with electricity. The heating coils are the same as those used for soil-heating cables. These coils are wound around -inch pipe which is run around the inside of the greenhouse. A thermostat controls the heat.

Automatic Temperature Alarm

An automatic temperature alarm-a thermometer hooked up to a bell-is good crop insurance. An unexpected cold night, failure of electricity, or trouble with your heating system might cause you to lose an entire crop. So that a power failure will not affect it, the alarm operates on batteries or dry cells. When greenhouse temperature drops below a pre-set mark, the thermometer actuates the bell. The bell for our greenhouse alarm is placed just outside our bedroom door. Thus we are able to hear it even in the noisiest stormy night.

Ample light and ventilation are essential in any greenhouse, while heating, humidification, and cooling must be considered in most operations. What you need will depend on where you are located and the crops you grow.

Heating

There are many types of heating units. Choose one which will keep the temperature of your greenhouse at desired levels for the full 24 hours. With any of the nationally advertised heating systems, spare parts are easily purchased. This is a good feature as it may save you time (and thus money) in case of a breakdown.

Hot Water and Steam Heat

In cold areas, hot water systems using coal, oil, or natural gas are the most popular for greenhouses.
If you have a large enough household heating system, you may be able to pipe hot water into the greenhouse pipes. This furnishes economical heat. But if the greenhouse is very large or is located over 100 feet from the household boiler, it may be better to install a separate system. Hot water furnishes an even, warm temperature minus the harmful fumes that are produced by some portable-type heaters. With a separate hot water system, it is necessary to install a boiler. The boiler can be automatically fired with oil, stoker, or gas, thermostatically controlled, or hand-fired with coal. If it is fired by hand, it should have sufficient capacity to run for 10 or more hours without attention.

Automatic firing and thermostatically controlled temperatures are a saving in time and money. They also assure more accurate heating. I use oil for heating my greenhouse. The system is inside the greenhouse annex. Units burning natural gas can be safely installed directly in the greenhouse or in an open attached unit. If you are using coal, artificial gas, or a mixture of natural and artificial gas, the boiler must be placed in a separate room or building, since fumes from these fuels are detrimental (sometimes fatal) to plant life.

The heated water circulates through pipes or fin radiation. I have fin-type radiation. Each foot of fin radiation has several times the radiating surface of a foot of standard pipe, and much less footage is required to maintain desired temperatures. For easy calculation, 1 foot of 2-inch fin-type radiation will equal about 6 feet of standard 2-inch pipe. These figures vary with the size of the fin and the number of fins per foot. The hotter you need to keep your greenhouse, the more pipe or fin sections you should have.
Steam heat, which also utilizes piping or fin radiation, is cheaper to install but it dries out the air and the plants.

21. A hidden row of fluorescent lights and a waterproof tray converted
this counter in my study into a beauty spot-and a sales display area-
for some handsome gloxinias. (Courtesy, Town Journal)

THE WARM HOUSE

The actual temperature range of a warm house is 60 to 70 degrees during winter nights. However, most of those who grow African violets, gloxinias, and so forth, as well as foliage plants of tropical origin and nature, find they get more rapid leaf growth and plant increase when the night temperature is 2 to 5 degrees higher than that range. The warm house is also used for growing many of the “stove” plants described in old garden encyclopedias and English gardening books.

FLOWERING PLANTS FOR THE WARM HOUSE

(Winter night temperatures: 60-70 degrees.)

Spring

Acacia Bromeliads
Aeschynanthus (various species)
(Trichosporum) Calceolaria
Amaryllis* Camellia
Arum* Carnation
Azalea Cineraria
Begonias Epiphyllum
(Tuberous,* semperflorens, Episcia
some rex) Freesia*

20. This lean-to may be a bit cramped for the grower but not for the
plants, and it will produce dollars. Every inch of space is organized. Note
the electric cable for automatic control of the ventilators. (Photograph
by Gottscho-Schleisner)

Geranium Kohleria*
(Pelargonium) Primrose
Gloxinia” African violet
Haeman thus * (Saintpaulia)
Kalanchoe Streptocarpus

Summer

Achimenes* Datura
Begonia Fuchsia
(Tuberous,* semperflorens) Geranium
Bouvardia (Pelargonium)
Bromeliads Gloxinia*
Campanula Gloxinera*
Canna* Impatiens
Crinum* Oxalis*
Cup-and-Saucer Vine Passiflora
(Cobea scandens) Petunia

Autumn

Begonia Chrysanthemum
(Tuberous,* semperflorens) Gloxinera*
Bromeliads Salvia
Canna* Vallota*

Winter

Ardisia Cyclamen*
Azalea Gardenia
Carnation Hyacinth*
Chrysanthemum Narcissus*
Cineraria Primula
Citrus Rivina humilus
Coleus Solanum

The cool greenhouse

In the cool house the night temperature in winter should be about 55 to 60 degrees with the usual rise of 10 degrees during the day. In this temperature range, you can grow a variety of plants including all of those suggested for the unheated green-

18. The free-standing greenhouse of Mrs. Marion Hughes, Galesburg,
Michigan demonstrates the convenience of slat shading; it can be rolled
down whenever needed, in end or side sections, as dictated by the sun.
(Photograph by Hughes)

house, as well as the plants in the following list, and your heating costs will be far less than those in a warm house of the same size.

Flowering plants for the cool house

(Winter night temperature: 55-60 degrees.)

Spring

Aquilegia
(Columbine)
Azalea
Browallia
Camellia Carnation
Cineraria Clematis
Clivia* Lachenalia*
Convallaria Lilium*
(Lily-of-the-V’alley) * Nasturtium
Freesia a (Tropaeolum)
Geranium Rhododendron
(Pelargonium)

Summer

Achimenes* Clematis
Agapanthus* Morning Glory
Asarina (Convolvulus)
(Maurandia) Cup-and-Saucer Vine
Begonia (Cobea scandens)
(all types) Crinum *
Bougainvillea Datura
Cacti Fuchsia
(Some varieties) Habranthus0
Caladium* Hoya
Calceolaria Hydrangea
Campanula Impatiens
Canna* Lantana
Carnation

Autumn

Bignonia Mignonette
Browallia Nerine*
Chrysanthemum Salvia
Fatsia Streptocarpus
Flowering Maple Vallota*
(Abutilon)

19. Profit “right in your own back yard.” Could the neighbors, or anyone,
resist taking home some part of this lush preview of spring? (Greenhouse
of Ruth Marie Peters; photograph by Roche)

Winter

Begonia Chrysanthemum
(Fibrous-rooted) Cineraria
Bouvardia Cyclamen*
Carnation Stocks
Christmas Rose
(Helleborus Niger)

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 coldest 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, seedling 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 alata9
Crocus* Jasmine
Cyclamen neapolitanum* Saxifraga
Erica Solanum
Fatsia Viburnum
Freesia* Violets