Tech Solutions

What can I do to make sure my plugs get off to the best start possible?
Providing the optimum environment can decrease germination time, improve uniformity and increase the number of seeds that germinate. Germination carts and growth rooms are used by growers to provide this environment and to ensure seedlings get off to a good start.

Critical factors for germination include moisture, oxygen, temperature and light. Select a growing medium that has good water-holding capacity, adequate drainage and allows good contact with the seed. Some growers have found that seed priming — partially hydrating the seed first — provides more uniform germination.

Temperature is also important. Extensive testing by USDA and several universities has found that each species has a range of temperature that is best for germination. For some plants such as marigolds, almost complete germination takes place at any temperature between 50°F and 85°F. Other plants have a much narrower range, such as freesia that germinates only between 55°F and 65°F.

Light requirements vary with plant species. Some seeds require light, some don’t and some don’t care. Some seeds are pretreated with light before they are sold. Once germinated, it’s important to provide adequate light to prevent stretching.

Fluorescent lamps are the common choice for providing the light needed to keep seedlings growing after germination. Install strip lamp fixtures evenly over the growing area. Although T12 and T8 fluorescent lamps are most common, the highest efficiency can be obtained by using the new T5 high output lamps. Cool white or a mixture of cool white and warm white work best. The fixtures can be mounted horizontally above the plants.

Seed companies and the extension service are good sources for providing the optimum environmental requirements for different plant species and cultivars.

Although many growers germinate their seed in a greenhouse, a germination cart or germination room can provide a better environment. In addition, a separate cart or germination chamber/room saves energy by not having to start the greenhouse for a couple of weeks during the coldest part of the winter.

Small Budget Solution
Building or purchasing a multi-tray germination cart is an inexpensive way to create the proper environment. Movable shelves provide space for different size containers. Thermostatically controlled electric heat tape installed on the lowest level can provide the heat. Enclosing the cart with clear polyethylene or double wall polycarbonate retains moisture. A commercial model in two sizes is available from Carolina Greenhouses in Kinston N.C., (800) 635-4532; www.carolinagreenhouses.com.

By spacing the shelves 12-18 inches apart and hanging fluorescent lamp strip fixtures underneath the shelves, the germinated seeds can be left to grow for a couple of weeks before moving them into a greenhouse. This saves energy by not having to heat or cool the greenhouse. A light level of 25 to 35 lamp watts per square foot of fluorescent light is adequate for most seedlings. USDA research has shown that the initial optimum growth rate continues for a period when the seedlings are moved to the greenhouse.

Large Budget Solution
Growers that need more space for seed germination usually set up a growth room. This separate insulated room has heat and ventilation to keep the temperature and humidity at the ideal level.

The room is usually set up with fixed shelves spaced 15 to 18 inches apart to allow room for fluorescent lights and the seed trays. Shelves should be sized to best utilize the space and lighting. To eliminate the need for benches, some growers place seed trays on carts and move the carts into the room. This makes handling more efficient.

For germination only, a thermostatically controlled electric heater will provide the heat needed. In a larger room, a unit heater is less expensive to operate. Heat requirements depend on the level of insulation provided. Air circulation from a small fan can help to keep the temperature uniform and reduce dead spots.

If lights are used, they will provide more than enough heat to keep the air temperature above 70°F. During cool periods, excess heat can be vented with a small exhaust fan and intake louver. During warm periods, refrigeration may have to be used. One way to lower the heat load is to stagger the lighting by operating half the lights for 12 hours and the other half for the other 12 hours. Excess heat can also be ducted to an adjacent greenhouse or headhouse area.

Wall and ceiling surfaces should be painted with a white acrylic paint to provide a reflective surface that can be washed down easily. The floor should be painted and have a drain for water.

The electrical system should have adequate capacity for the lights, heater and fan. Total up the wattage of the equipment that could be on at the same time. Due to the possibility of nuisance tripping, ground fault circuit interrupters (GFCIs) are generally not required. It is better to connect all equipment to a good grounding conductor that is run with the circuit wires. It is also desirable to install high-low temperature and power-off sensors to the alarm system.

A germination room must be tight to retain moisture and to maintain a high relative humidity. After an initial, thorough wetting, seed flats can be irrigated by hand with a mist nozzle. A humidifier can be installed to add moisture to the air. A relative humidity of about 95 percent is recommended to maintain growing media moisture levels.