growing seedlings under a growlight

farmerjohn · March 25, 2012

I have tried growing seedlings under a growlight. They always turn out tall and spindly and fall over. What am I doing wrong???

marc_groleau · March 25, 2012

Hello farmerjohn,

I'll tell you how I grow them. I have no problem with spindly plants.

>I use one cool white and one warm white lamp in each fixture.
> Hang the fixure very close to the seedlings. maybe two- three inches above the tallest plant. I check daily and raise as needed.
> I don't let them get too warm. I don't want the lamps to heat the seedlings. That hasn't been a problem though. If you suspect the temperature under the lights is above 80 degrees, place a fan some distance from the lights but aim the fan in that direction.
> Keep the soil moist. If the lights dry out the soil, spritz water on the soil in the morning before turning on the lights and spritz at night when you shut them off if needed.
> I shut the lights off at night. I probably put the lights on for about 14 hours each day.
> Let the night time temps get down to just room temperature or down to as low as 65 degrees or so if possible.

Spindly plants are usually a result of not enough light or too high temperature.
If you do these things I don't think you'll have a problem.

Marc

Granite26 · March 25, 2012

Agree....temp too high or lack of light. Those grow lights need to be right on top of the seedlings. Once my toms germinate I turn down the heat in my shop where I start the sedlings. I go from 70-75 degrees down to 55-60.

ddsack · March 25, 2012

As well as keeping them close to the lights, putting a fan on them for at least part of the day helps thicken and strengthen the stems.

marc_groleau · March 26, 2012

Ditto on the fan ddsack.

TightenUp · March 26, 2012

keep the light super close and add a fan. i put a fan on a timer with the lights the day i sow the seeds so they are exposed to a little breeze from the start. just a little desk fan works perfectly

delaware · March 26, 2012

I just use the two bulb 48 inch shop lights with regular fluorescent bulbs. i keep the seedlings about 4-5 inches from the bulb. I use the 50mm Jiffy peat pots that expand in water and keep them under the clear cover dome. Keep them just barely damp so you don't et that fuzzy fungus. I keep the lights on 24/7 and the room is a porch that I never heat over 65 degrees this time of year. I've had extraordinarily good success with very strong fast growing great looking seedlings.

Everyone has their own success story and style and they will all be different and subject to disagreement. I went for the easiest, no frill, cheapest setup and it works. you'll figure out you're own best system too after experimenting. Good luck and keep us posted!

rsg2001 · March 26, 2012

Delaware, after they germinate you don't need the clear cover dome; clearly you've had success but it does increase the chance of fungus or mold to keep it on. The 65 degrees is a perfect temp once they have started to grow; no need to keep it hotter.

As for the advice to FarmerJohn, I'm 100% with those who say keep the lights just a couple inches above the seedlings, and turn them off at night, or have a timer that has 12 hours on, 12 hours off. I've done pretty well with that formula.

March 25, 2012	#1
farmerjohn Tomatovillian™ Join Date: Mar 2012 Location: Tennessee Posts: 2	growing seedlings under a growlight I have tried growing seedlings under a growlight. They always turn out tall and spindly and fall over. What am I doing wrong???

March 25, 2012	#2
marc_groleau Tomatovillian™ Join Date: Jan 2012 Location: Rhode Island Posts: 444	Hello farmerjohn, I'll tell you how I grow them. I have no problem with spindly plants. >I use one cool white and one warm white lamp in each fixture. > Hang the fixure very close to the seedlings. maybe two- three inches above the tallest plant. I check daily and raise as needed. > I don't let them get too warm. I don't want the lamps to heat the seedlings. That hasn't been a problem though. If you suspect the temperature under the lights is above 80 degrees, place a fan some distance from the lights but aim the fan in that direction. > Keep the soil moist. If the lights dry out the soil, spritz water on the soil in the morning before turning on the lights and spritz at night when you shut them off if needed. > I shut the lights off at night. I probably put the lights on for about 14 hours each day. > Let the night time temps get down to just room temperature or down to as low as 65 degrees or so if possible. Spindly plants are usually a result of not enough light or too high temperature. If you do these things I don't think you'll have a problem. Marc Last edited by marc_groleau; March 25, 2012 at 09:06 PM.

March 25, 2012	#4
ddsack Tomatovillian™ Join Date: Jan 2006 Location: Northern Minnesota - zone 3 Posts: 3,220	As well as keeping them close to the lights, putting a fan on them for at least part of the day helps thicken and strengthen the stems. __________________ Dee **************

March 25, 2012	#3
Granite26 Tomatovillian™ Join Date: May 2009 Location: Western WI Posts: 359	Agree....temp too high or lack of light. Those grow lights need to be right on top of the seedlings. Once my toms germinate I turn down the heat in my shop where I start the sedlings. I go from 70-75 degrees down to 55-60.

March 26, 2012	#5
marc_groleau Tomatovillian™ Join Date: Jan 2012 Location: Rhode Island Posts: 444	Ditto on the fan ddsack.

March 26, 2012	#6
TightenUp Tomatovillian™ Join Date: Mar 2011 Location: Jersey Posts: 1,183	keep the light super close and add a fan. i put a fan on a timer with the lights the day i sow the seeds so they are exposed to a little breeze from the start. just a little desk fan works perfectly

March 26, 2012	#7
delaware Tomatovillian™ Join Date: Mar 2012 Location: delaware Posts: 25	I just use the two bulb 48 inch shop lights with regular fluorescent bulbs. i keep the seedlings about 4-5 inches from the bulb. I use the 50mm Jiffy peat pots that expand in water and keep them under the clear cover dome. Keep them just barely damp so you don't et that fuzzy fungus. I keep the lights on 24/7 and the room is a porch that I never heat over 65 degrees this time of year. I've had extraordinarily good success with very strong fast growing great looking seedlings. Everyone has their own success story and style and they will all be different and subject to disagreement. I went for the easiest, no frill, cheapest setup and it works. you'll figure out you're own best system too after experimenting. Good luck and keep us posted!

March 26, 2012	#8
rsg2001 Tomatovillian™ Join Date: Jun 2006 Location: New York Zone 6 Posts: 479	Delaware, after they germinate you don't need the clear cover dome; clearly you've had success but it does increase the chance of fungus or mold to keep it on. The 65 degrees is a perfect temp once they have started to grow; no need to keep it hotter. As for the advice to FarmerJohn, I'm 100% with those who say keep the lights just a couple inches above the seedlings, and turn them off at night, or have a timer that has 12 hours on, 12 hours off. I've done pretty well with that formula.