Grow Lights / Greenhouses

kygreg · March 7, 2009

Probably a dumb questions but that has never stopped me before.

When my tomato seeds germinate, I put them under a growlight within 2" of the light.

The school where I teach has a large greenhouse in the agriculture dept. The FFA club starts hundreds of tomato and other seeds there. It is heated, but there are no grow lights and the seedlings seem to do well.

Do commerical growers and home growers with greenhouses use growlights close to the seedlings and if not how does that affect legginess.

Thanks.

**Dukerdawg** · March 7, 2009

Greg, I could be wrong, but I believe greenhouse growers just use natural sunlight. After all, plants have grown before man invented the light bulb!

Duane

svalli · March 7, 2009

If the greenhouse is located far away from equator and the plants are started or grown during winter, the commercial growers need to use artificial light. Up here for commercial tomato growers the second biggest cost after heating is light. In many places they are now experimenting with more econimical LED lights. These lights can be easily set shining just to the plants and that decreases the 'light pollution' coming out from the greenhouse. Some people who live close to the greenhouses are actually complaining about the lights.

kygreg · March 7, 2009

So if I started tomato seeds in the school greenhouse; they should do fine without a growlight close to them?

The greenhouse is heated and has lights in the ceiling.

dcarch · March 7, 2009

One watt of light will give you 3.41 BTU of heat.
One watt of heat will give you 3.41 BTU of heat.

If you have good reflectors to prevent light from escaping, then you will have light and all the free heat.

If you have heaters, all you get is just heat.

The law of conservation of energy applies here.

dcarch

Ruth_10 · March 7, 2009

A plant in a greenhouse will get far more light than those under fluorescent lights, unless (a) the greenhouse is far from the equator as in Svalli's situation or (b) the growlight setup has been jazzed one way or another. Even a plant outside in the shade will be receiving more light than those under fluorescent lights. I'd go for the greenhouse.

March 7, 2009	#1
kygreg Tomatovillian™ Join Date: Jun 2007 Location: kentucky Posts: 1,019	Grow Lights / Greenhouses Probably a dumb questions but that has never stopped me before. When my tomato seeds germinate, I put them under a growlight within 2" of the light. The school where I teach has a large greenhouse in the agriculture dept. The FFA club starts hundreds of tomato and other seeds there. It is heated, but there are no grow lights and the seedlings seem to do well. Do commerical growers and home growers with greenhouses use growlights close to the seedlings and if not how does that affect legginess. Thanks.

March 7, 2009	#2
Dukerdawg Growing for Market Moderator Join Date: Jan 2006 Location: Westland, Michigan Posts: 861	Greg, I could be wrong, but I believe greenhouse growers just use natural sunlight. After all, plants have grown before man invented the light bulb! Duane __________________ May I aspire to live my life so that I may be the man my dog thinks I am.

March 7, 2009	#3
svalli Tomatovillian™ Join Date: Feb 2006 Location: Vaasa, Finland, latitude N 63° Posts: 838	If the greenhouse is located far away from equator and the plants are started or grown during winter, the commercial growers need to use artificial light. Up here for commercial tomato growers the second biggest cost after heating is light. In many places they are now experimenting with more econimical LED lights. These lights can be easily set shining just to the plants and that decreases the 'light pollution' coming out from the greenhouse. Some people who live close to the greenhouses are actually complaining about the lights. __________________ "I only want to live in peace, plant potatoes and dream." - Moomin-troll by Tove Jansson

March 7, 2009	#5
dcarch Tomatovillian™ Join Date: Jun 2006 Location: NY Posts: 2,618	One watt of light will give you 3.41 BTU of heat. One watt of heat will give you 3.41 BTU of heat. If you have good reflectors to prevent light from escaping, then you will have light and all the free heat. If you have heaters, all you get is just heat. The law of conservation of energy applies here. dcarch __________________ tomatomatomatomatomatomatomatomatomatomatomatomato matomato tomatomatomatomatomatomatomatomatomatomatomatomato matomato tomatomatomatomatomatomatomatomatomatomatomatomato matomato

March 7, 2009	#6
Ruth_10 Tomatovillian™ Join Date: Feb 2006 Location: MO z6a near St. Louis Posts: 1,349	A plant in a greenhouse will get far more light than those under fluorescent lights, unless (a) the greenhouse is far from the equator as in Svalli's situation or (b) the growlight setup has been jazzed one way or another. Even a plant outside in the shade will be receiving more light than those under fluorescent lights. I'd go for the greenhouse. __________________ --Ruth Some say the glass half-full. Others say the glass is half-empty. To an engineer, it’s twice as big as it needs to be.