Flourescent lights/leggy seedlings?

[Mark]

I'm curious if I'm doing my lighting right for my seedlings. I have one of the Professional Jiffy Greenhouse 72 peat pellet seed starting kits, and I'm starting my seeds for my garden.

Anyway, I have two 18" flourescent fixtures- one with a GE Plant & Aquarium tube, and one with a GE Chroma 50 tube. I set the fixtures/tubes directly on the plastic greenhouse top, and rotate them each day, so that the plants get an even mix of Chroma 50 and Plant & Aquarium light.

The vast majority of the seeds sprouted quick, and are growing madly- most of them have their cotyledon leaves & stems almost to the top of the plastic greenhouse top- they look kind of spindly right now. No true leaves have shown up yet.

Is this a problem, or is it common for the cotyledon leaves to shoot up really high and quick? I read that lack of light will cause leggy plants, but I'm not short of light with my setup, am I?

[Cereus-validus.....]

You are a bit ahead of schedule, aren't you? Its only February and in most places, you are long way off before it is safe to put plants outdoors.

What plants are you growing from seeds anyway?

You should try to have your plants as close to the lights as possible without burning them.

What length day are the lights set for?

If you use a light meter, you will see that the light intensity emanating from plant lights is far less than what you would get outdoors or in a greenhouse. Its even less than you would get in a shaded locality outdoors.

Another problem with growing under artificial lights is poor air circulation and too high humidity. That can cause the seedlings to come up spindly and too weak to survive for long. You need to get a small fan and set it on a low setting just to move the air around.

[fleemo17]

[Nick Maclaren]

In article , "Mark" writes: |> |> Is this a problem, or is it common for the cotyledon leaves to shoot up |> really high and quick? I read that lack of light will cause leggy |> plants, but I'm not short of light with my setup, am I?

The usual cause is too much heat relative to the light, which is a nightmare in the UK - we can get leggy seedlings OUTSIDE in extreme circumstances!

Try keeping them cooler, at least from when they start to emerge from the compost.

Regards, Nick Maclaren.

[Mark]

Zone 8a. Mid-March is usually the latest frost we'll see around here (Dallas, TX area).

Ah. Didn't do that, although I'm only about 2-3 days off from when everything sprouted.

About 15-16 hours a day- 9 a.m. to about midnight or so.

I'll try that - will a ceiling fan running in the room work? I already have that going, but I can set up another one.

[simy1]

you are definitely short of light. the other pieces of advice are pretty good, and they will improve your light efficiency and prevent damping off, but they won't solve your main problem, which is too little light. You can evaluate things yourself. In full sun, with the sun overhead you get about 600W/m2 of light. With the sun at 45 degrees, you get 420W/m2. Each 72-cell tray is about 0.18m2, so you should be coming in with close to 80W/tray. Those fluorescents are fairly efficient, but they are not 100% efficient, so make that

100W/tray. I found that the only thing that helps is a sunny window, and taking them out to full sun as soon as feasible.

[fleemo17]

You're right on target then. Most seeds should be planted 6 to 8 weeks before the last frost.

Definitely take off the lid. It'll help with air flow, and if there's a lot of condensation on the lid, it may be cutting down some of your precious light.