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What distance should my light be from my plants?

OlderGrower

Member of the Month: Dec 2015
Im using a 1000 watt Mh light, 20 inches from 13 day old plants. My light meter says 100k -110k lumens. Temp 80-88 degrees. Plants seem to be fine so far but im worried i am overdoing it. Are my temps or lumens to high? My cooling duct fan is on the way, hopefully soon! TY, im new to growing!
May I make a small suggestion. Why not grab a few CFLs or even a t-5 or t-8 fluorescent fixture to veg under. 1,000 watts of light for 13 day old plants is like renting a semi tractor trailer to go grocery shopping. Plenty of room for groceries but a whole lot of wasted space, or in the 1,000 watts case wasted energy. Just a thought, though if you have 30 plants in 1 gallon pots I understand, or 6 plants in 20 gallon pots I get it.
 
I know someone who uses led. His is pink and you can't change from red to blue.ya they are freaking bright! I'm using 1000w mh. That's bright!!
 

gr865

Well-Known Member
If anyone here grows vertical I have a question.

I want to run a 5 plants vertical grow in a 4x4x6.7' tent, I would like to use a 400W Eye Hortilux Super HPS, the min distance I can plant the light is 13". Will the 400W give me the light I need for the 5 plants. I hope so as I can't afford a new light setup till after the first of the year.

Here is a picture of the screen layout not yet in the tent. At this setup I have around 28" between the screens so with the light in the center, hung vertical will be around 14" from the screen. I will be tying the plants to the screen.



Thanks,

GR
 

TorturedSoul

Member of the Month: May 2009, Oct 2010, Sept 2017
I am simultaneously using 2 CFL bulbs:

1. 325W
2. 150W
Can you post a picture of the 325-watt one? I have never seen such a large CFL. The largest size CFL I have ever personally had was only a 250-watt one, although I have heard that they make 300-watt ones. A 325-watt one must be quite large. Here is a picture of one that was part of a group which I tested for someone once (along with a more common "household size" one for comparison, which I think was either a 23-watt or 26-watt one). IIRC, the one on the left was only a 125-watt one. It couldn't have been much higher-wattage, because the > 200-watt ones that I was testing all required mogul sockets instead of the regular-sized residential sockets.



What distance should my bulbs be from the plants? They are currently about 2-4 inches away, I can put my hand very close to the bulb and it isn't uncomfortable
IF you truly have a 325-watt CFL, I seriously doubt that you'd want it 2" from your plant. High-wattage CFLs produce some serious heat. Now that I think about it, my guess is that you actually have a 65-watt one.
 

KonopCH

New Member
Hello everyone, I have 250W HPS sylvania gro-lux (dual spectrum). My plants are 14 day old, light is 55cm from plants. Can I lower it to 25cm or not in veg.state? I have autoflowers.
 

Bud Borne

New Member
really hoping for a response im using a 400w dual spectrum LED and need to know how far my light should be from my plants they are currently in the seedling stage (around 8 days) and arent growing as fast as they should be, theyre only now growing the second level of leaves, im assuming its the lights the humidity good and same with the moisture level of the soil.
 

brownie420

New Member
Hey guys,

I'm just shy of 12 hours away before i start my first grow. I got Heavyweight Fast & Vast Auto Autoflowering Feminised Seeds (3-pack). All 3 seeds are looking great, cracked and tap root starting to come out nicely. I will be putting them into Promix HP, with 5.8pH/low ppm water.

I bought a HPS setup for later on in the bloom stage, but I want to use CFL 6500K color temp bulbs for seedling/early veg.

I have 3 bulb outlets i can put directly above the three 3-Gallon pots I plan to use. I purchased the 6500K color temp bulbs: 1 package of 4 - 860 Lumen bulbs, 1 package of 1600 lumen bulbs and 1 package of 2250 Lumen bulb.

What combination of the CFL bulbs should i be using to get the best lumens for max seedling/early veg node growth?

If someone could help me out I would be very grateful ! .. and love you long time :)
 

TorturedSoul

Member of the Month: May 2009, Oct 2010, Sept 2017
I'm just shy of 12 hours away before i start my first grow.
WooHoo! :thumb: .

I bought a HPS setup for later on in the bloom stage, but I want to use CFL 6500K color temp bulbs for seedling/early veg.

I have 3 bulb outlets i can put directly above the three 3-Gallon pots I plan to use. I purchased the 6500K color temp bulbs: 1 package of 4 - 860 Lumen bulbs, 1 package of 1600 lumen bulbs and 1 package of 2250 Lumen bulb.

What combination of the CFL bulbs should i be using to get the best lumens for max seedling/early veg node growth?
Are they all 6,500K? Can you add those double-socket Y adapters to your existing three sockets? Do you have a fan blowing gently (that you can increase as the plant grows) to move the heat that the bulbs produce away from the plants? If so, I would aim for 1" away after the plants have established themselves, and a little more initially. I guess you could start at four to six inches and lower them an inch every few days to a week. Remember that the intensity of the light decreases at the square of the distance, and CFLs are not intense light sources. You don't need to max out your lighting immediately after the seedlings break ground, but they should be given an adequate amount. I see that you are growing an auto-flowering strain; what lighting schedule are you shooting for? If it is less than 20 hours light to four hours darkness, you could start them at that amount and reduce the amount of light-hours an hour or two per week until you arrive at your target schedule..

You could add 2,700K light at a ratio of 1:3 6,500K during the vegetative growth phase and, at the switch to a 12/12 light schedule, reverse that ratio for three 2,700K bulbs to one 6,500K one for flowering. Obviously, this works best if you can mix the bulbs so that each plant gets light in that ratio.

For best results, place all the CFL bulbs in a horizontal orientation, with reflectors over them. Bulbs only produce a small percentage of their output at the one end of the bulb - and none at all from the end that screws into the socket. Simple reflectors can be made out of aluminum soda pop (et cetera) cans. A Dremel tool is your friend. You can cut a straight line down the side of a can, connecting a cut on each end that goes along the circular edge. If you cut the ends completely off of the can, you will need to figure out a way to connect it to your bulb, lol. But if you cut it correctly on the socket end, it will go around the plastic part of the bulb. You can open the can up and you have your reflector. If you leave the "open" end attached, you can bend it up a little to help reflect and light that hits it downward towards the plant. If you want to get fancy, you can figure out how to put a long shallow crease on the side of the can that is directly opposite the vertical cut you made (also requires adjusting the angles of the curved ends that go around the bulb to allow for the change caused by the crease). This modification mimics the area in open HID reflectors, and helps ensure that light at the "top" (actually, the side pointing upwards) of the bulb, when it is reflected back towards the plants), does not get reflected right back at the bulb.

Even with CFLs, decent reflectors really help.

A fan blowing across your plants - such as an oscillating fan - will, as mentioned, carry the CFLs' heat away from the plants. It will keep the leaves in motion, which will encourage stems that are healthy and strong. (You can help by gently "twisting the stems back and forth, along the long axis of the plant - but be careful when the plants are very small and tender that you do not cause damage by breaking the stem or uprooting the plant.)

If the seedlings show signs of needing more light, reduce the distance from the lights to the plant. But keep it at one inch, minimum. After they are established, if you have enough illumination, the plants can easily grow an inch per day.

Are you going to leave them in one-gallon pots, or will you be transplanting them into larger final homes at some point? I have read that your strain can get reasonably sized, so (I would think) a three to five gallon final pot size would be better.
 

crippiekeeper

New Member
Re: What distance should my light be from my plants?
That is a complicated Question you should check with the manufacture of your lights. But the guy above me is wrong the optumum leaf temperature is no where close as a matter of fact if you take that advice and keep your leaf temps at 70 degrees your plants might get sick and die. IM SUPPORTING MY INFORMATION WITH EASY DOCUMENTATION FROM LEADERS IN THE INDUSTRY. YOUR PLANT LEAF TEMPS NEED TO BE AT 88 DEGREES FOR OPTOMAL GROWTH.Effects of Different Artificial Grow Lighting Technologies on Leaf Surface Temperature"What is the Ideal Leaf Surface Temperature?
So what is the ideal leaf surface temperature for plants? This is unfortunately a question without a single, simple answer as many factors influence the ideal.

Multiple types of metabolic reactions exist within every plant, and each has a different optimal temperature range. Primary metabolism (photosynthesis) is obviously the most important; without it the plant will not survive. Optimal temperatures for desirable secondary metabolites must be considered as well, especially if the plant is grown specifically for the secondary metabolites.

The optimal leaf temperature range for photosynthesis in many plants is between 15 °C and 30 °C (59 °F to 86 °F) for normal atmospheric concentrations of CO2. There are many exceptions; arctic- and alpine-adapted plants typically require cooler temperatures, while desert-adapted and plants using C4 photosynthesis prefer it warmer. (There are two slightly different chemical reactions for photosynthesis, called C3 and C4; the variant a plant uses is determined genetically.) CO2 supplementation will also generally raise the optimal photosynthesis temperature, so the ideal LST for photosynthesis is dependent on environmental conditions as well as the type of plant.

Secondary metabolic reactions can have a huge range of optimal temperatures; many plants have even evolved responses specifically triggered by exposure to cold or hot temperatures to better adapt to their surroundings. For example, some plants produce proteins with anti-freeze properties when exposed to cold.

In short, the ideal leaf surface temperature depends on the species / variety of the plant, overall environmental conditions, as well as what the plant is being grown for. Only experimentation can determine an ideal range for LST for a specific plant variety in a specific set of conditions."
 

crippiekeeper

New Member
In short, the ideal leaf surface temperature depends on the species / variety of the plant, overall environmental conditions, as well as what the plant is being grown for. Only experimentation can determine an ideal range for LST for a specific plant variety in a specific set of conditions."
 

TorturedSoul

Member of the Month: May 2009, Oct 2010, Sept 2017
YOUR PLANT LEAF TEMPS NEED TO BE AT 88 DEGREES FOR OPTOMAL GROWTH.
It varies. Not just by strain, but by the amount of light and CO₂ the plants are receiving. IIRC, that 88°F reference assumes that the plants are receiving as much light as they can process (at that temperature ;) ), and under average non-supplemented CO₂ levels (400ppm, or near enough it makes no difference). When things are balanced... Dropping the temperature - or the CO₂ - causes the plant to be unable to process as much light. Decreasing the light means that a slightly lower temperature might be considered optimum. That's why, these days, a range of 77°F to 86°F.

But the guy above me is wrong the optumum leaf temperature is no where close as a matter of fact if you take that advice and keep your leaf temps at 70 degrees your plants might get sick and die.
I assume you mean the post above yours - which is mine. I never mentioned temperature, except to suggest that the person have a fan blowing to move the bulbs' heat away from his plants (and to encourage healthy stem growth). Perhaps you actually meant someone else's post? If you would like to use the quoting function next time, you can quote the text that you are actually referring to.

BtW, most cannabis plants won't "get sick and die" at 70. No, it is not the best temperature for yield (et cetera). But the plant should live unless there are other factors at work.

IM SUPPORTING MY INFORMATION WITH EASY DOCUMENTATION FROM LEADERS IN THE INDUSTRY. YOUR PLANT LEAF TEMPS NEED TO BE AT 88 DEGREES FOR OPTOMAL GROWTH.
Would you like to share the reference you "speak" of, lol? Or at least mention which facet of the industry they are involved in? There are (a few) scientists doing research in plant physiology. There are growers - both large-scale commercial growers and personal growers that have smaller setups (but ones that they might have tuned for years). There are light component manufacturers, and businesses that assemble completed lights, and ones that sell them (sometimes the lines blur, IOW, a seller might assemble his/her own products). Et cetera. I like reading, so I'd probably still be interested, regardless of the source's specific area of expertise (and/or motivation).

IIRC, there was a time when a recognized "guru" published a book on cannabis - in which he stated that crushing up birth control pills and adding them to the water given to cannabis plants would encourage a higher percentage of females, lol.
 

Daisy Melton

New Member
yes i believe so , ive grown with LED and they do work but it takes twice as long ... the best thing about them is that they r cheep to run and dnt cause much heat. i now grow with hps and LED to get the best of both worlds .
which brand do you use? The led light
 
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