JARS v36n3 - The Indoor Growth Chamber

The Indoor Growth Chamber
Mark Konrad, M.D., Sewickley, PA

The indoor growth chamber described in this article is a unique structure which offers advantages to people interested in growing rhododendron seedlings. Temperature and humidity, two important necessities to young seedlings, are well controlled.

The walk-in chamber is designed to hold three, uniform fiber glass trays measuring twenty by forty-eight inches. The trays are positioned on the sides and far end of the enclosure, thus leaving a small space for easy maintenance (See Figure 1). The overall size is approximately sixty-four inches wide, eighty-four inches long and seventy-seven inches high. Polyethylene film held in place by thumb tacks is draped over a framework of two by fours and is also hung over the doorway. The cost excluding fluorescent fixtures is well under a hundred dollars.

Interior of growth chamber.
Fig. 1. Photograph showing interior of growth chamber.
photo by Mark Konrad

Large open trays of water are then placed beneath the benches which can also be constructed with plastic film over a wood framework edging. Next, the bench trays are filled with stones and water. Both of these increase the humidity and evaporation controls the heat. The temperature never goes above 74°F. with the lights on or below 68°F. with the lights off.

One daylight and one General Electric Wide Spectrum bulb are used in each, forty-eight inch, fluorescent fixture. The lights are placed about two feet above the plants, but the exact height may depend upon particular growing needs. Since the plants are exposed directly to the artificial light, this could represent an additional advantage for growth.

Surprisingly, a large number of seedlings can be started with this method because each tray holds twenty-four, five-inch azalea pot saucers. After germinating on milled sphagnum moss, seedlings are transplanted to the saucers and mature in a relatively sterile, porous medium including Canadian peat moss, milled sphagnum moss and perlite. It is not essential to use a fan for air circulation, but it may become necessary if unsterile ingredients are added to the mix. (See Figure 2).

Seedlings approximately 100 days old.
Fig. 2. Photograph showing seedlings
approximately 100 days old.
photo by Mark Konrad

Because of the small size of the chamber, carbon dioxide exhaled within the chamber might be of additional value. Being indoors, there is no need to heat the chamber and a convenient basement location eliminates any possibility of utility failure which can occur during adverse weather.

This structure approaches the function of growth chambers which are designed to control the environment. For the person interested in this exciting work, a growth chamber such as the one described may be an ideal solution in controlling the degree of involvement especially for those who find it necessary to ration their time.