New Grower My first Auto grow
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I grow in tlo soil that is mild enough that I can plant seedlings directly into and I get the same light tips on new growth occasionally.
Thanks!! I'm hoping time will tell lol
That looks like light stress from a gas discharge (CMH, HPS, HID) where the heat of the lamp damages plant tissue. You can destroy tissue (necrosis) with an LED but you have to work at it.
I just googled "light stress" something something and the page I read recommended that growers put the back of their hand under the light to see if the light is too close. No mention of that advice being wrong for LED's. LED's, in most cases, don't have any IR diodes and those lights that do don't put out anything near the amount of IR that gas discharge does (think cafeteria heat lamp).
Latter part first - not necessarily but I suspect that would be the case. The reason why that can't categorically be the case is that so many things in that grow are now different. The plant is older, the leaf tips are now dead, and the soil has a different nutrient mix. In addition, unless you're using clones, those plants are different. I grow from seeds and, my last three grows have been "Twins" after the movie of that name (Schwarzenegger and Danny de Vito) where one plant is at least a foot taller than the other(s). Unless you're growing clones, each plant is different and may react very differently to inputs in the grow environment.
Burnt leaf tips is just a classic fertilizer issue. Google "cannabis leaf tips burned" and the first hit "Burnt tips are always a sign of over-fertilization." And it's got to be true because it's on the internet.
Another indicator is where is it impacting the plant. Light damage impacts the parts of the plant that are closest to the light source so if your leaf tips aren't in the canopy, it's not a light issue.
"correct range" - cannabis will grow at light levels between 64µmols and 800-1000µmols in a non-CO2 enhanced environment, as long as the other factors in the grow environment are not constraining factors. That latter part is important because I was on a thread where the grower was getting "light burn" at 500±µmols. After a lot of back and forth, it turned out that he wasn't watering correctly and the roots at the bottom of his plants were soaked. Barring something like that, cannabis is a total light whore.
Haivng said that, you'll get a good grow at 600µmols. No question about that at all. On the other hand, a grow that's exposed to 900µmols in flower will yield about 20% more than a grow at 700µmols. Important words "in flower" because that's what the study measured - IIRC, they did 600 in veg and then up to 1500 or 2k µmols in flower. As PPFD increase, plant yield, crop yield, and crop quality increase at about 5% for each 50µmols of light.
Bugbee has published a couple of studies that show an almost linear increase but he did not specify (and I haven't bothered to research it) if the light levels were different in veg vs flower. The reason I didn't research it is because it doesn't matter to me. My approach is simple - get the plants to light saturation point (800-1000µmols) ASAP.
A lot of growers don't use those light levels and get good crops. Shane at Migro and growlightmeter.com both recommend DLI's in the 40's and neither of those sources provide citations for their recommendations. Seeing that they clash with published research, I choose to go with published research. Shane sells a 260 watt light in the 2' x 4' market and his light level recommendations are well below, for example, what the Mars SP 3000 generates and what the Growcraft X3 generates (I have both of those lights). I have no reason to doubt that Shane honestly that 260 watts is a good light level and, to go along wit that, he sells a brilliantly-designed series of light that undercut the competition on price, one of those reasons being that the cost of his 260 driver is probably lower than the 300 and 330 watt drivers that are in the Mars and the X3. That's not a coincidence and, "some people" might think that he has tempered his recommendations so that he can sell a cheaper product. I have no reason, or interest, in his motives.
If you're so inclined, listen to the new video that Bugbee and Shane released on YouTube. Shane asks Bugbee about light levels and you can hear the incredulity in his voice when Bugbee responds. That surprised me - I would have thought that Shane would have read all of Bugbee's research so he would have known the answer but, based on the sound of Shane's voice, it seems that he's taken aback by the response. I haven't listened to the whole video yet but, when I saw that Shane was talking to Bugbee, I listened to parts of it and, sure enough, Shane was a little bowled over.
That's pretty "in the weeds" (pardon the pun) for discussing light levels but, as I see it, being able to increase yield (as well as quality) by 20% just by turning up the lights is a pretty big deal. Second, as research has shown, the value of cannabis is so high that the value of the increased yield is significantly greater than the increased cost of electricity. Home growers might see if differently but, even at the 31¢ per KwH that I pay here in the People's Republic of California, I'll gladly increase my wattage to get my plants into the 900µmol range.
DeBacco does a couple of different videos on this. His data seems to be coming from Bugbee primarily but he lays things out in an easy to digest manner.
Here are some screenshots from his videos.
Thanks! I'll have to check out the videos. The majority of published articles I see on the subject come from Chandra Et Al but some of this stuff might be a bit dated (2008 - 2015) . I'd agree I prefer to rely on peer reviewed published literature.Latter part first - not necessarily but I suspect that would be the case. The reason why that can't categorically be the case is that so many things in that grow are now different. The plant is older, the leaf tips are now dead, and the soil has a different nutrient mix. In addition, unless you're using clones, those plants are different. I grow from seeds and, my last three grows have been "Twins" after the movie of that name (Schwarzenegger and Danny de Vito) where one plant is at least a foot taller than the other(s). Unless you're growing clones, each plant is different and may react very differently to inputs in the grow environment.
Burnt leaf tips is just a classic fertilizer issue. Google "cannabis leaf tips burned" and the first hit "Burnt tips are always a sign of over-fertilization." And it's got to be true because it's on the internet.
Another indicator is where is it impacting the plant. Light damage impacts the parts of the plant that are closest to the light source so if your leaf tips aren't in the canopy, it's not a light issue.
"correct range" - cannabis will grow at light levels between 64µmols and 800-1000µmols in a non-CO2 enhanced environment, as long as the other factors in the grow environment are not constraining factors. That latter part is important because I was on a thread where the grower was getting "light burn" at 500±µmols. After a lot of back and forth, it turned out that he wasn't watering correctly and the roots at the bottom of his plants were soaked. Barring something like that, cannabis is a total light whore.
Haivng said that, you'll get a good grow at 600µmols. No question about that at all. On the other hand, a grow that's exposed to 900µmols in flower will yield about 20% more than a grow at 700µmols. Important words "in flower" because that's what the study measured - IIRC, they did 600 in veg and then up to 1500 or 2k µmols in flower. As PPFD increase, plant yield, crop yield, and crop quality increase at about 5% for each 50µmols of light.
Bugbee has published a couple of studies that show an almost linear increase but he did not specify (and I haven't bothered to research it) if the light levels were different in veg vs flower. The reason I didn't research it is because it doesn't matter to me. My approach is simple - get the plants to light saturation point (800-1000µmols) ASAP.
A lot of growers don't use those light levels and get good crops. Shane at Migro and growlightmeter.com both recommend DLI's in the 40's and neither of those sources provide citations for their recommendations. Seeing that they clash with published research, I choose to go with published research. Shane sells a 260 watt light in the 2' x 4' market and his light level recommendations are well below, for example, what the Mars SP 3000 generates and what the Growcraft X3 generates (I have both of those lights). I have no reason to doubt that Shane honestly that 260 watts is a good light level and, to go along wit that, he sells a brilliantly-designed series of light that undercut the competition on price, one of those reasons being that the cost of his 260 driver is probably lower than the 300 and 330 watt drivers that are in the Mars and the X3. That's not a coincidence and, "some people" might think that he has tempered his recommendations so that he can sell a cheaper product. I have no reason, or interest, in his motives.
If you're so inclined, listen to the new video that Bugbee and Shane released on YouTube. Shane asks Bugbee about light levels and you can hear the incredulity in his voice when Bugbee responds. That surprised me - I would have thought that Shane would have read all of Bugbee's research so he would have known the answer but, based on the sound of Shane's voice, it seems that he's taken aback by the response. I haven't listened to the whole video yet but, when I saw that Shane was talking to Bugbee, I listened to parts of it and, sure enough, Shane was a little bowled over.
That's pretty "in the weeds" (pardon the pun) for discussing light levels but, as I see it, being able to increase yield (as well as quality) by 20% just by turning up the lights is a pretty big deal. Second, as research has shown, the value of cannabis is so high that the value of the increased yield is significantly greater than the increased cost of electricity. Home growers might see if differently but, even at the 31¢ per KwH that I pay here in the People's Republic of California, I'll gladly increase my wattage to get my plants into the 900µmol range.
DeBacco does a couple of different videos on this. His data seems to be coming from Bugbee primarily but he lays things out in an easy to digest manner.
Here are some screenshots from his videos.
View attachment 1548560
View attachment 1548561
I laughed at it must be true b/c it's on the internet lol.
As far as the leaf tips I can certainly back off the fertilizer as I was increasing it in steps.
My lights at best I might be able to hit 700 PPFD due the the number of plants vs lights it's sort of a trade off.
Definitely watch Shane from Migro's videos on YouTube.
Very down to earth person.
I've enjoyed reading your post.
I just started my first post on here about my auto grow, and my second indoor grow ever.
Very informative site!
Very down to earth person.
I've enjoyed reading your post.
I just started my first post on here about my auto grow, and my second indoor grow ever.
Very informative site!
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