The availability of light and the intensitiy and color of this light, is essentiial for the development and health of your plants and for that reason directly influences the succes of your marihuana Crop.
Indoors in gardens and tents, we use lights for our cultivations of weed, mostly led, lec or hps lights. The distance between your light and your plants will determine the succes of your harvest. But how do we know if the plants get enough, too much or too less lights? Luckely the plants tell you!
Distance of lights is always a dillema. A difference of an inch or a few centimeters will make much difference in lumen (light intensity) and for that reason a big difference in how much energy your plants can absorb and give.
When you are pushing your lights to be as close as possible, it can be that you will see in the top small leafs at highest points buds, become pale, lighter green that, when you do nothing, will change into yellow and curl into dry. The most of other leafs lower on plant will remain green at first but your marihuana plant is suffering. When you notice in time and raise your lights these pale leafs will change into green again. When you wait it becomes irreversable and the burning of the leafs will spread. An other clear sign of lights being to close is the becoming partly white of parts of the top buds, the closest buds get bleached by the intensity of too much ligh closeby. Your plants can also show their overdose of light by producing fox tails in your buds, see our blog post earlier. Main visible difference with burning from the roots is that these burns will show on all leaves, old and new, while light burn will show on leaves that had this light stress. It can also be recognized in development of changing color in the leafe, see the pictures above.
And what if your lights are too high and light is too weak? This can easy be noticed by the stretching of the plant stimms between the branches and leaves while not developing new branches, leafs or internodes, your cannabis plant is only stretching and reaching out for more light! After that your plants become weak and will not develop no more but finish stage they are in instead.
Recommended and most used distances from top marihuana plant to lightbulbs are
For hps lights 600w:
# seedlings and clones - use the ceiling as your limit. Pit them as high as possible for at least 7 days, use only half of your lights first few days.
# grow stage 18/24 - 60-70 cm / 25.6 inch
# flowering period 12/12 - 50-65 cm
For lec lights 630w:
# seedlings and clones- put your lights as high as possible for at least 7 days. Use only half of your lights first few days
# veg stage 18/24 - 55-60 cm / 22.6 inch
# flowering stage 50-60 cm / 21.7 inch
For led lights
# see the recomendations of the producer of your lights.
Be aware that plant takes more time to show too much light is given using lec as with hps light, as if there is a delay in showing you. This means you have to react quiker to avoid irreversable burning of leaves and plant when using lec.
It has to be mentioned that certain marihuana strains can handle a big load of light and liking it, while other cannabis strains have difficulties with high Lumen. This means that when you found your perfect hights for your lights, it does not necessaraly mean your next cultivation with an other strain will have the same perfect distance to your grow lights.
Link to previous blog Part 4:
Link to next blog Part 6:
Link to blog foxtails: