Susan and community garden friends, A few notes to add on light tubes and seed starting ....
Fast growing seedlings like tomatoes like to stretch to get as close as possible to their light source. If the light source is more than one to two inches from the seedlings, the plants are more likely to become spindly. Keeping the fluorescent lights close to the plants will help plants to develop stockier stems, along with periodically rotating the plants under the lights. >From physics, light intensity (as measured in lumens) decreases with the square of the distance from the light source. At a distance of 3 inches from the light source, plants receive 1/9 the light intensity as compared to a distance of 1 inch. At a distance of four inches, light intensity decreases to 1/16 the lumens of a distance of 1 inch. Another factor affecting plant growth is the quality and spectrum of the light source. Gardeners may remember the acronymn ROYGBIV, which represents the colors of the light spectrum (red, orange, yellow, green, blue, indigo, violet.) In a general sense, the blue portion of the spectrum influences plant growth, while the red portion influences flowering. Cool white fluorescent tubes have high light output in the blue spectrum. Warm white tubes have high light output in the red spectrum. Some people recommend using one cool white tube and one warm white tube per fixture, but a better solution is to use wide spectrum fluorescent tubes, which have a pink light that combines high output in the red and blue spectra. Full spectrum fluorescent tubes are an effective but more expensive choice that tries to replicate sunlight by balancing out light energy across the spectrum. During the past few years, I've tested plant growth with several light tubes and fixtures, including T-8 light tubes and T-12 tubes. In the tests, the overall most reliable and cost effective performance in seed starting came from 40-Watt T-12 GroLux Wide Spectrum tubes. A close second in performance were the full spectrum 32 Watt T-8 tubes. These tubes use 20% less electrical energy but their smaller diameter (as compared to the T-12 tubes) resulted in a bit less dispersion of light. If you're interested in building your own indoor garden with a T-8 light fixture, I've posted plans on our web site at http://www.burlingtongardens.org/classic_indoor_garden.html. If making a homemade unit, look for a light fixture with a larger reflector and at least 3 inches distance between the tubes. The greater the dispersion of light, the less rotating of plants to promote even growth. Friends of Burlington Gardens sells four models of Vermont Indoor Gardens with wide spectrum light tubes. The models at http://www.burlingtongardens.org/IndoorGardens.html have excellent light fixtures with wide spectrum bulbs, are priced affordably, and shipped via UPS. Proceeds from indoor garden sales are used to help develop new community gardens in Vermont. Seed starting can be great fun, and I hope that many community gardeners will give it a try. Jim Jim Flint, Executive Director Friends of Burlington Gardens 180 Flynn Ave Studio 3 PO Box 4504 Burlington, VT 05406-4504 802-861-4769 www.burlingtongardens.org Message: 3 Date: Sat, 31 Mar 2007 06:10:59 -0700 (PDT) From: Susan Shear <[EMAIL PROTECTED]> Subject: Re: [Community_garden] flluorescent bulbs To: community_garden at list.communitygarden.org Message-ID: <557634.1016.qm at web31304.mail.mud.yahoo.com> Content-Type: text/plain; charset="iso-8859-1" I just took a seed starting class at the University of Connecticut. The instructor told us that he uses shop lights that hangs from chains and reguluar flluorescent bulbs. He said the key was to keep the light 3" from the top of the seedlings (thus the need for the chains) because light that is too far away from the seedlings causes spindly growth. - Susan
