At what distance will a 400 watt mh/hps cause a plant to stretch

[VancouverBCBud]

I know that I should have my bulbs as close as possible to the plants without burning them but I do not currently have the best setup for heat extraction so I need to keep the light at least 15 inches away to keep the temp under 85 during the day. I'm just wondering how far away you can get without hurting plants growth, or will every inch further cause a little slower/stretchier growth?

 

[DirtyMcCurdy]

15 inches isn't bad. What is your setup like?-How are you controlling temps? I am just not seeing how moving it a few inches is controlling your temps that much, unless you're referring to canopy temps. Do you have sufficient air-flow?

 

[VancouverBCBud]

Yes, canopy temperature, if you want to see the setup I have some pictures on my grow journal. In short it isn't great but its working well for things I just had around the house. I know people usually say to keep temps under 80 but is that referring to canopy temperature, directly in the light or the air temperature in the shade?

 

[DirtyMcCurdy]

Yes, canopy temperature, if you want to see the setup I have some pictures on my grow journal. In short it isn't great but its working well for things I just had around the house. I know people usually say to keep temps under 80 but is that referring to canopy temperature, directly in the light or the air temperature in the shade?

I usually hover in the 80-82 area. I don't get into checking canopy temps really, my thermo just sits about canopy height. I also use 400s. You will have to keep an eye on the leaves. Your plants will tell you if they are getting too hot. Some of mine are less than a foot away from the bulb and showing no signs of stress.

 

[jacksthc]

in veg and early flower its best to have the light close to the top of the canopy 10"-12"

Temp upto 35c are fine early flower and in mid to late flower lift the light as the plant stops growing and it can affect the buds, using a fan to blow over the top of the canopy should reduce canopy temp.

Canopy temps is the max temp in the room and you want to keep it below 30c in late flower also you need the min temp to stay above 10c light out as It could stunt the growth (I aim for at leat 15c )

 

[VancouverBCBud]

in veg and early flower its best to have the light close to the top of the canopy 10"-12"

Temp upto 35c are fine early flower and in mid to late flower lift the light as the plant stops growing and it can affect the buds, using a fan to blow over the top of the canopy should reduce canopy temp.

Canopy temps is the max temp in the room and you want to keep it below 30c in late flower also you need the min temp to stay above 10c light out as It could stunt the growth (I aim for at leat 15c )

Don't temps at 35c slow growth unless you have extra co2 or a strain that can handle high temps? My biggest plant seems to be fine under this lamp but the seedlings second sets of real leafs look kind of deformed, could that be heat stress?

And do you guys think this looks like heat stress?

 

[jacksthc]

It should affect all the leaves at the top of the canopy, level with the seedling if its down to heat stress, plants can't handle high temps if the humidty is low

whats the max/min canopys temp/humidty ?