Starting seedlings under fluorescent light is one of the best ways for gardeners to get a jump on spring. Because seedlings grown under lights receive the same amount of light day after day, regardless of the weather outside, you won't have to worry about leggy, unhealthy plants during a dark and gloomy spring. As long as you have a good grow-light system, you can produce your own nursery quality transplants at home for a fraction of the cost.
Supplying the Right Light
The best way to provide adequate light for your growing seedling is with cool-white fluorescent tubes. They duplicate the color spectrum of sunlight more closely than any other type of artificial light and are the most efficient to operate. Don't worry about buying "grow lights" designed especially for starting plants. The inexpensive shop lights commonly available at large home stores work just as well and they are far less expensive. Shop lights come with a pair of 4 to 6 foot long fluorescent tubes in a fixture that hangs from chains and cost somewhere between $12.00 and $30.00 (with reflectors). The chains attached to the fixture make it easy to raise and lower the height of the lights as your seedlings grow. One shop light should provide enough light for two full-size flats.
Many seedlings prefer extra warmth as they begin to grow. In general, seeds germinate best if the soil temperature is around 75 F. However, some cool-natured plants (like lettuce and snapdragon) prefer cooler germination temperatures around 65 F. Place containers planted with seeds in a warm place, keeping in mind that the lights from your grow system will generate only a small amount of heat. You can also buy moisture-proof soil-heating cables or pads at garden centers or by mail order. Place them beneath containers to provide steady and even warmth. After the seeds germinate, normal room temperatures between 65 and 75 F are sufficient to keep them growing vigorously.
Tips for a Successful System
The grow-light system you choose will depend on your available space, budget, and the amount of seedlings you plan to grow. A good system allows you to start your seedlings under the same conditions each year, so you can fine-tune your methods and continue to improve your results. From the single flat of seedlings growing under lights on the kitchen counter, to the complex light system in your basement, whatever you decide, here are a few tips for getting the most out of your lights.
- Growing seedlings need lots of light for sturdy growth, so keep your grow lights on 16 hours a day. Light tubes last longer if they are not turned on and off unnecessarily. Buy an inexpensive timer to shut them on and off.
- Suspended your lighting as close to the leaves of the seedlings as possible (within 2 to 4 inches) without allowing the fluorescent tubes to touch the leaves.
- Light tubes produce less light near the ends than in the middle. Choose the longest ones you have room for, and rotate the position of the seedlings every few days to ensure they receive even amounts of light.
- Dust-covered fluorescent tubes can decrease the amount of light available to plants. Try to keep them as clean as possible. Paint surfaces near the fixtures such as shelves and walls with white paint to reflect more light. You can use mirrors or aluminum foil to reflect additional light from nearby windows or fluorescent fixtures back onto your seedlings.
- Over time, fluorescent lights produce less light. Replace them before they burn out completely.