If you install a master control system of watering, the whole business is simplified. For bench plants, a length of plastic hose perforated the entire length with minute openings can be attached to a faucet and laid on the soil between the plants. When water is needed, you simply turn on the faucet far enough to force water through the openings and then leave it on until soil is well soaked. A more permanent arrangement consists of fastening a flexible plastic pipe with spray nozzles around the perimeter of the bench area. Either method can be controlled automatically by an electric water valve and a 24-hour time clock. The clock, wired in series with the valve for automatic operation, is set to control the duration of the watering cycle.
A new system for watering pot plants as well as bench plants is now available in kit form. A molded rubber distributor is placed between the pots, and water is supplied directly to each pot through hollow plastic tubes attached to the distributor. Tubes are approximately 5 feet long, and are easily held in place in the pot by a lead weight at the end. Small plants or pots take one tube; two or more are necessary for large pots, seed flats, or big benched plants. A kit contains two water distributors with 20 outlet tubes each, and one 10-foot length of hose to connect the distributors.
This system may be made automatic with time-clock control, and one manufacturer markets a control panel for just this purpose. It includes two time clocks, an electric water valve with strainer, two hose bibbs, and an electric switch for manual or automatic operation. The panel is preassembled and ready to be plugged into a polarized 110 volt 60 cycle electric outlet. Just connect to your water supply with pipe, copper tubing, or hose, and you are ready to operate the system. With this control panel, plants can be watered individually and automatically every day. One time clock, a 24-hour type, turns the system on and off at pre-selected times, usually mid-morning. Since this 24-hour clock has a minimum operating time of 18 minutes —far too long for a watering cycle—a second fast-cycle clock is required to reduce and control the watering interval. As a rule, only a few minutes watering per day is required with a kit system. However, the duration of the watering period can be adjusted by changing the settings to suit local water pressure, weather, and greenhouse conditions. The 24-hour clock also allows for skip-a-day control, and you can set the system to water on pre-selected days. An electric switch permits manual operation when you want it. If you set the switch to "manual," water will be supplied to the entire system, taking care of all plants until you reset the switch to "automatic." The parts in the kit are assembled on exterior-grade plywood that can be mounted anywhere in the greenhouse convenient to water and electricity. The system can be enlarged and extended simply by adding extra hose bibbs.
If you are growing orchids or other plants that benefit from periodic fine spraying, you may want to install a mist system. With this an electric valve, equipped with a strainer, controls the flow of water to the mist nozzles. The valve comes with female pipe threads on both inlet and outlet. It controls water pressure up to 150 pounds per square inch and operates on 115 volt, 60 cycle, AC current only. As in the case of the watering system described above, two time clocks are required. One 24-hour clock turns the system on during the day, off at night. The second clock, a fast-cycle repeating time clock, controls the duration of the mist cycle, usually in multiples of six seconds —six seconds on, twelve seconds off; or twelve seconds on, eighteen seconds off. It is easily adjusted to suit individual installations. Each nozzle mists an area approximately 36 inches in circumference, and you can install as many nozzles as your greenhouse requires.
If the hose used for watering is equipped with a spray nozzle, this may suffice for misting your plants, but keep the spray fine so water will evaporate quickly. If you do not have a spray nozzle, place your thumb squarely over the end of the open hose, exert an even steady pressure, and the force of the water against your thumb will produce a fine mist that can easily be directed.
If it is impractical to furnish a water line directly to the greenhouse, get a big container vat, barrel, tub that can be filled from a hose attached to an outside faucet on your house. From this you can get water throughout the winter. It takes only a moment to open the inside control valve to allow the use of the hose, and to shut it off again to prevent freezing of the water line in cold weather. I had such an arrangement in my second greenhouse. A great preserving kettle, placed at the end of the center bench directly under the NoVent heater, was filled from a hose connected to the outside house supply. The blast from the heater warmed the water so there was no chilling of plants, and from the kettle a certain amount of moisture evaporated into the atmosphere. This helped overcome the inevitable drying effects of heat supplied in winter. Of course, dipping water from a kettle takes a little time, but it is a practical and economical method. Naturally you won't want to do this longer than you have to, but it is a means to an end if the greenhouse budget is tight the first year.