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2. The Story of My Profit-Making Greenhouse

The highlight of the story of my own greenhouse—a 12-footer plus workroom-annex—is that it paid for itself in 9 months. I will give you a few of the salient points of its con­struction, but mostly I'll describe operation, for it has been successful enough to warrant expansion to twice the size—and after only 4 years. And I will tell you something about some other successful ventures which will give you still more ideas about building and operating your own greenhouse.

The cost of my greenhouse and annex, including hired labor, was just $900.00, and it required only 3 weeks to build. The foundation was laid on May first and we were able to plant on May twenty-first.

Attached to our home, and opening into the greenhouse, is the 11-foot wide by 552-foot long annex-workroom. The green­house itself is small, about 9M feet wide by 12 feet long. It was built to allow for expansion. The heating system was therefore made larger and more expensive than was necessary for the original under-glass setup. But as I mentioned earlier, the greenhouse was soon doubled in size, which put the oversized heating system to full use.

The greenhouse is built out from the west side of the house, so its long sides face north and south. Some of the plants I grow for profit are sun-lovers, others thrive in shade or semi-shade. Those needing the most sun are grown on the south side. My selection of plants is varied, yet they all do well in daytime temperatures of 70 to 75 degrees F., with the usual night drop to 60 or 65 degrees. Indeed it is amazing what different kinds of plants can be accommodated in the same house.

Building My Greenhouse

All buildings in northern zones must have footings (founda­tion extensions) which extend below the frost line. Greenhouses are no exception. In my area, footings must be dug to a depth of 3½ feet so frost will not heave the foundation and crack the greenhouse glass.

We dug and poured the footings ourselves (a measure of economy), but we hired a cement contractor to lay the actual foundation and the greenhouse walk or aisle. The foundation is made of cement blocks; it is 5 cement blocks high and 6 long. The walk is made of cement slabs. This work and the materials cost $285.00 and the job was finished in 1 day. Within 2 days the cement had set and we went on with the rest of the con­struction. The actual details of fastening supports and cross-pieces, installing doors, ventilators, and so forth are not relevant here. In the first place, they would require endless pages of text and diagrams—and such data are easily obtained from any number of commercial greenhouse construction sources. Also, there is no one "best" way to build a home greenhouse—there are dozens! The construction as well as the type will depend on the requirements of your climate and what you desire (and can afford). Incidentally, construction guides are available from lumber firms as well as greenhouse builders. I will offer, how- ever, certain points of information that are generally helpful, whether you build your own greenhouse or have it built by a construction firm

4.  This view of the south side of my Minneapolis home greenhouse shows the double decking.   (Note shading compound on glass.)   Large plants including a lemon tree, grow on the sunny top deck of the bench, gesneriads on the shaded lower deck. (Photograph by Roger Groff)

For instance, we chose redwood, sturdy and rot-resistant, for the greenhouse framework. It has proved to be a wise choice. Trenglaze, a non-hardening putty, was used to bed and seal the glass panes (called "lights" in the trade). We used non-rusting brass screws throughout. Also, we used double-strength greenhouse glass. This costs about 20 per cent more than single strength, but it is many times more durable. In the 4 years I have had this greenhouse not a single pane has broken or cracked. The lights, cut to fit by the manufacturer, measure 20 inches wide. On the roof the lower ones are 20 by 42 inches. These are larger than many greenhouse builders use, but they mean much less construction work, admit maximum light to the plants, and minimize drafts. A layer of pea rock covers the ground flanking the walks.

Finally, we painted the outside cement blocks pale green, the framework white, to blend with our green-and-white stucco home.

For Maximum Space

The first year the greenhouse was a two-bench type with 3-foot wide wooden benches running the length on either side of the center aisle. As orders increased, we needed more grow­ing space. Accordingly, we installed a double-deck bench sys­tem. This provided a larger growing area and also helped with the shading problem.

A full length bench about 2 feet wide, with legs 2 feet high, was placed on top of each of the two original benches. Three-inch deep galvanized metal trays were set into each of these top benches to prevent dripping. While these top-level benches greatly increased plant space, they also cut off some of the light from the first-level benches. However, this turned into the traditional blessing in disguise, for the partly shaded area of the lower-level benches proved ideal for African violets. And the plant space close to the glass along the south side on the first-level benches, and all of the space on the top decks, still re­ceived full sun. The increased bench space also reduced crowd­ing. Plants must not be crowded if they are to be healthy and grow symmetrically. A free circulation of air is always neces­sary to prevent fungus and other troubles.

In your greenhouse, you may work out the use of space a little or a lot differently. It always depends on what you want to grow and also on the limitations your particular site may have as to light. It's usually a good idea to solve some of the space problems gradually as experience indicates.

On the south-side, top-deck bench, I place potted seedlings of gloxineras (hybrids from crosses involving gloxinias and rechsteinerias). Here, too, I place starting tubers as well as plants which have finished flowering and are ripening seeds. On the north-side top deck, I set flats of episcias and rooted glox-inera cuttings. Trailers such as aeschynanthus, columnea, cissus, ceropegia (rosary vine), and plectranthus take up little space and do a good job of covering the sides of the galvanized tray.

On the lowest bench, close to the windows on the south side, I have slipper gloxinias and their South American relatives, the red- and orange-flowered rechsteinerias, as well as more glox­ineras, a few species amaryllis and pink polka-dot plants. The rest of the first-level bench area, shaded by the top deck, is devoted to African violets. Additional space is gained by hang­ing baskets from the ceiling. I plant kohleria, columnea, and some orchids in these. I think hanging baskets always make a greenhouse more attractive.

5. I use this off-the-floor cabinet to store insecticides and other chemi­cals, fragile containers for arrange­ments, and so on. Note fluorescent lighting beneath cabinet. (Photo­graph by Roger Groff)

6. The top of this cabinet in the utility room, adjacent to my green­house, serves as a potting bench. The shelves hold many greenhouse supplies and shipping materials, arranged for easy access. (Photo­graph by Roger Groff)

A Shade Section

In my greenhouse I make good use of the shaded, often use­less, under-bench space. Here, on both sides of the center aisle, suspended under the first-level benches, are 3-foot-wide by 11-foot-long shelves. They make a good home for low-light-require­ment plants, such as the handsome-foliaged rex begonias, anthuriums, and variegated ivies like Gold Dust with yellow-sprinkled leaves, and the small green-and-white-leaved Jubilee. Mature plants of a number of philodendrons, as well as cuttings of these plants, also do well under the bench. Several kinds of episcias, the blue-flowered Fanny Haage and the red-flowered Episcia cupreata, likewise grow to perfection in this low-light area. All of these can be good profit-makers.

Held-over mature tubers and bulbs in pots are rested by laying them on their sides on the ground layer of pea rock under the shelves and benches.

Greenhouse Annex

As I have said, in addition to the greenhouse we have an annex that connects the greenhouse to our house. This is really a part of the house and it provides valuable extra space. It also contains the greenhouse heating boiler, our household pump, the pressure sprayer, and a storage cabinet.
A triangular shelf, roughly 12 by 52 inches, juts out below the south windows. Under this shelf are fastened two 40-watt fluorescent tubes. Here I propagate some seedlings and root special cuttings in a clear plastic box.

There is a wide doorway or opening between the greenhouse proper and the annex, so plants grown in the annex have ap­proximately the same conditions as those in the greenhouse.

Two 6-foot glass shelves are spaced across the two south-facing windows of the annex. These are fine for larger specimen plants of gloxineras, gloxinias, and amaryllis.

The storage cabinet is 6 feet high, 2 feet wide, and 1 foot deep. Shelves of varying heights give ample room here for storing liquid plant food, insecticides, tools, labels, and so forth.

In a utility room, which opens off the greenhouse annex, I have a large cabinet for dry fertilizers, clean pots, drainage ma­terials, and special potting media, such as milled sphagnum moss, osmunda fiber, and vermiculite. I use the top of the cab­inet counter as a potting bench. If the utility room weren't so handy, I could use the space below the south windows in the annex to store some of these materials. This is what you may have to do. It all depends on the possibilities of your own layout.

Heating the Greenhouse

In northern areas the heating plant is the most expensive part of a year-round greenhouse. Since I decided, with expan­sion in mind, on a rather large heating apparatus, it cost $500.00 installed. Actually, a smaller, possibly secondhand heat­ing plant costing about a quarter as much, would be adequate for this 10- by 12-foot house. The hot water boiler is powered by fuel oil. Tall, stainless steel smoke stacks remain free of rust despite condensation. Hot water circulates through fins on pipes which go around the inside of the greenhouse. The cost of heating per season, September through May and part of June, averages $100.00.

Ventilation and Water Supply

The ventilation arrangement in my greenhouse is of the sim­plest type. Four of the roof lights fit into redwood sash. Hand openers, made by attaching grooved sticks to hinges on the sash, can be operated from the floor. The vents can be raised just a crack or opened completely. During the summer one of the glass panes in the east wall is removed and a screen inserted in its place to let in more air (while keeping out insects). Directly below this is an 8- by 28-inch vent with sash fasteners for easy opening, to permit ventilating as required throughout the year.

In winter, when a glass replaces the screen, I slip a shelf across the east end of the greenhouse. This is a fine place for a few vines or other salable plants.

Water for the greenhouse comes through the household water system. A mixing faucet in the greenhouse provides room-temperature water—which often means the difference between full vigorous growth and the unthrifty appearance of plants that have been shocked by irrigation with ice-cold water.

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