Temperature and light distance for seedlings

[Crow]

Hi All,

I have some week old seedlings going (Northern Light) under a 400 watt MH. The distance from the light to the plants is only about 12" but I have a small fan passing air and the thermometer reads in the 75°F range. My hand over the plants is just warm - no real heat. The plants seem OK. The seeds were started and the plants continue to grow, in some 3" cow pots.

The question is: Should I / Can I, set my plants closer to the light to achieve a warmer temperature, more like 85° F? I can go as close as 8" without any light/heat issues using the hand test.

OR - is the mid 70s° a good temp and leave it at that?

The fan and lights are off for 6 hours every night, at which time the room temps dominate and these days that's about 68° F.

Warmer = closer to the light.

Thanks for any advice.

Crow

[Smokesteve]

Honestly I think your too close for week old seedlings or at least more than close enough. People and weed like the same temps mid 70s with a light breeze is a great temp.

[Crow]

The too close issue is why I ask. At the 12"-13" height I can maintain the mid-70s°. Raising the light means I loose heat UNLESS I turn off the fan.

Alternatively - my little grow is currently in a big room that is in the 68° range (the plants are likely in that temp range at night) so I could move the plants to a more enclosed area - raise the light a foot or so and regulate the temps in the "closet".

Are the plants being bombarded with too much MH light at this time? No matter the temperature should I raise the lights?

In a few weeks I intend to transplant to larger post and then move to a dedicated insulated space with LED lights and the one MH light. There I will control the temps, air movement and light distance more to standards discussed throughout GWE.

Thanks.

[Crow]

I just realized that adding a comment does not keep the thread alive. Help please. I'm just trying to achieve best results with limited resources and a paucity of experience.

Crow

[kingfish]

With seedlings I use my light to adjust the temp. Put a thermometer on you pots and move the light up or down to get the temp. Try not to go over 80 degrees. Some pictures would be nice. I should note that I use a T5 for vegging.

[Flockshot]

I like mid 70's F all the times. I would not go into the 80's unless I have to, but that is just me.

Remember that when people talk about the 'perfect' anything (light, nutes, temps, humidity, etc) that they are talking about their strain, in their setup, and their experience, and their spot on the earth.

If you look at all the 'ranges' in the GWE tutorials, and can keep your numbers within those ranges, you have a really good chance for success.

Just a note, that when you change from MH to HPS, that the HPS is a LOT hotter than MH so increase the distance significantly.