I've never used artificial lighting of any sort over seedlings.

flurescent lights tend to be the wrong type of light for good plant growth unless you buy the expensive tubes specifficaly for this.

personally I dont use lights.

Lacking artificial light, though, make sure that they get plenty of natural light, including at least 6 hours of direct sunlight for most plants. It's hard to recover stringy, floppy seedlings!

growth of seedlings seems to be very slow .when i used lights growth was alot faster.plenty of light in the greenhouse .the main reason i wanted to use natural light was to keep the bills down.ive noticed that stems of seedlings are abit elongated although not by much but enough to notice it.never had that problem under lights.there is buckets of light in the greenhouse so i dont know.i might supplement the lighting untill they get a pair of true leaves to make their own food then switch off.any further thoughts would be grateful.
brian

You would need a good light meter to prove it, but fluorescent lights close to the seedlings--18 inches or so--will be brighter than a gray day in the greenhouse. Fluorescents of the right type also provide some ultraviolet, which is blocked by plexiglas greenhouse panes, and is important for the development of the supportive tissues of plants.

ive put the lights and allready an improvement in growth.twin fluorescent lights are 3 inches from a tray of 72 seedlings and are growng better definitely.light is made up of 1 cool and 1 warm .in the trays are 72 lavender (english) ,1 tray of 72 red pansy seedlings and another tray of 72 lavender.

All sun lovers, so that makes sense to me.