2019 ASHS Annual Conference

Home gardeners often lack a suitable location for starting vegetable transplants. This can limit opportunities to use cultivars not readily available as transplants or to use season extension techniques if planting materials are not available when needed. One option is to sow seed in containers kept indoors if a location with suitable exposure to sunlight is available. However, in the absence of adequate lighting poor results are received when plants are grown indoors. Plant quality begins to decline at seedling emergence due to seedlings becoming etiolated and spindly. Further seedling development may be weak and plants may develop additional abnormalities. Various widely available and economical lighting products that can easily be supported over plants could be used to start garden seedlings if suitable plant growth can be obtained. Several types of lights available as units measuring approximately 40 in. by 6 in., including fluorescent and light emitting diode (LED) technologies were evaluated for starting vegetable plants using several varieties of garden lettuce Lactuca sativa L. as a test species. Following seeding, lights were installed over trays throughout the germination process and during two weeks of plant growth. Lettuce plants developing under either a "Active Spaces Daylight" fluorescent (D) or an LED "Shop Light" (S) were shorter and had a deeper green color than those developing under a fluorescent "Plant and Aquarium" (P) light. Photosynthetically active radiation (micro mol m^-2 s^-1 ) produced by the three lights at 2 cm from the sources were 71, 35 and 15, for sources S, D and P, respectively. The ratios of red to far red light were determined for the sources using a sensor designated for 660 and 730 nm. Ratios for S, D, and P, were 1.6, 1.5 and 0.75, respectively. Possibilities for using these lights for starting plants in a home environment will be discussed.