Introduction- Couple Questions w/ LED Grow

hi there welcome to GC ..couple of the pictures do look like heat stress edges curling up etc ..i dont know much about growing under LEDs ,,so some else may be about to tell you about height of the lights etc ....but i am sure theres a thread or three on the site about growing under LEDs ,,have a looksee around it may help you ,,,,mac,

 

shouldn't be the light as both lights give you 38 watts a sqft not near enough to burn if at correct distance. I would put the other one back up as one only gives you 19 watts a sqft. follow the owners manual for proper distancing. leds are made differently in how the bulbs are angled. proper distance is key in getting the most out of the spectrum provided. I would look into topping and training or force flower in 3 weeks to a month so the plants don't grow into your lights being blurples the plants need to be like 18 inches away or they will be burned. if you top and train or at least train you can stretch your veg out a little bit longer. personally I would return those and get another set of lights Grow Lights, Professional Lighting suppliers and manufacturers - Alibaba your lights are 615 watts you could have gotten better lights at 600 watts for 200 bucks saving you 280$ plenty for that ph meter which is as important as the water your putting in. I would agree with mac in heat stress do you have a temp and humidity reader? you may need 2 fans for 32 sqft of grow space I run a 6 inch cloudline in a 3x3 or 9 sqft of grow space and it barely keeps it cool enough. also the white leds the plants can be as close as they can take the heat emitted off the light. so you don't have to worry as much about flowering and light distance.

 

Do you have an infrared heat gun? (Aka Laser thermometer)
The leaves look like they are hot but those lights and your temp readings don't make sense to that. You have about 1200w total of lighting in that space which is decent coverage.

Since your ambient temps are pretty low (70 is low for LED, many run high 70's up to mid 80's if you have enough humidity) I'd say you are most likely over-watering as your VPD is pretty on target at 0.75-0.88 kPa

Try letting them dry out until they feel "light" to a lift test and then go from there.

Welcome to the community by the way!

 

yea drop that humidity 60 is a bit much 70 is over kill I keep mine at 39%

 

I disagree, when in veg VPD should be 0.6-1.2 kPa (And he's in that range with 60-70%), if he were to drop his humidity to 39% he would be at 1.53kPa which is at the top of the target for late flowering.

Dropping humidity at this point will do nothing but stunt growth as it will reduce proper transpiration.

I suppose one could argue that if a plant is overwatered, temporarily increasing VPD would help dry it out, but personally I'd rather just give it time before watering again to balance itself out.

 

I would take a pic w lights off. I also 2nd returning the blurple light. It’s old technology. Damn near will give me a seizure being around one.
RD

 

Would love to see some photos without purple light. I would guess overwatering. As someone else said, water by weight of your pots. Water when they get light. Don't water if they are heavy. I think everything else sounds good.

You're going to get a lot of input on your lights. As your budget is limited, know that your yields won't be awesome, but you will grow weed with your setup. As money allows, a different light is your first purchase.

Welcome and good luck!
☮️

 

I show signs of humidity damage with anything over 55% unless in seedling stage and anything below 30% so we can agree to disagree. also nothing about their plants look over watered I just didn't feel the need to call you out as you did me. I will add I didn't tell him to drop his to 39% I said drop it , I said I keep mine at 39%

 

What are the signs of humidity damage you refer to?

 

do you not know what humidity damage looks like you've took over dudes thread know it all

 

I was asking what damage YOU were referring to as humidity damage. The whole point of posting on an open forum is to have discussion. I didn't take over any thread, am simply replying to a discussion, Until I hit "Post Reply" on here you have posted more comments here than I have.

I'm not trying to start anything, I simply offered my opinion and then asked you to expand on your counterpoint to my opinion. I'm not above learning but I prefer to base my knowledge on science and evidence instead of just hearsay, and so far the horticulture science supports the VPD curve as the ideal place to be. No it's not required, you can grow plants outside it just fine, but to facilitate optimal photosynthesis having the right levels of transpiration is one of the factors.

 

Cycle after cycle my veg plants still grow with RH never above 30%. The low is often unreadable by the meter. Hitting the numbers on VPD charts is nice, but certainly not necessary.
RD
Edit: whoops on the test score

 

How Humidity Works
By Mark June-Wells, Ph.D.
What Can Happen When Humidity Is Unbalanced?

Plants acquire carbon dioxide from the atmosphere in which they are growing; this requires that the plants open their stomata and capture carbon dioxide. Opening the stomata also causes water to be drawn up through the plant from roots to shoots to the leaves and, ultimately, the atmosphere. This process causes the plant to acquire water from the soil medium, which is laden with nutrients. Therefore, the following can occur if humidity is not balanced correctly:

1. With very low humidity, the plant is drawing water from the soil at a very high rate, and if the humidity is too low, the plant is unable to draw water at a rate equal to loss through the stomatal openings. The result is that the plants close their stomata, which slows the photosynthetic process (due to carbon limitations) and leads to stress, slow growth and compromised yield. Under severely low humidity, the plant will wilt and die because even its protective mechanisms cannot offset the water stress imposed by the lack of atmospheric water.

2. When humidity is too high, the rate at which plants draw water from the soil is reduced because transpiration is slowed by the smaller-than-normal water gradient between the plant and the atmosphere. This can result in diminished nutrient uptake efficiency, which can lead to nutrient deficiencies. This phenomenon is particularly evident in the uptake of calcium.

Additionally, saturated media pH has a tendency to climb over time, which can also result in many nutrients (e.g., metals, phosphorus and calcium) becoming unavailable to the plant because of altered chemical interactions under elevated pH conditions.

What Are Optimal Humidity Levels?

While cannabis cultivation research is a growing field, scientific evidence characterizing optimal growing conditions has not been fully explored. Fortunately, a vast body of research exists in the areas of indoor and greenhouse cultivation of many food species. Some of these food crops are suitable surrogates for determining potential cannabis cultivation conditions because of similarities in natural, physiological and environmental requirements.

The general humidity range for indoor cultivation appears to exist between 60% and 75% for all growth stages. When humidity surpasses 80%, particularly during the lights-off phase, a higher risk of fungal, bacterial and viral infections exists. Conversely, if humidity drops much below 50%, crop photosynthetic efficiency may be affected and yield will suffer.

Based on peer-reviewed research in the field of indoor/greenhouse produce cultivation, the following relative humidity (RH) conditions would be suitable for indoor/greenhouse cannabis cultivation.

• Cloning: 70%-75% RH
• Vegetation: 65%-70% RH
• Flower: 60%-65% RH
• Night phase of flower: 55%-60% RH

Tips: Always be sure to avoid stagnant air during all light and dark phases and swap air to reduce humidity/carbon dioxide levels during light-dark-phase transitions. Finally, be sure your temperatures are suitable for optimal plant growth during light-phases (75°-80°F) and slightly cooler temperatures during dark-phases (~70°F).

Mark June-Wells is laboratory director for Connecticut Pharmaceutical Solutions (CPS), one of four licensed medical cannabis producers in the state. Dr. June-Wells holds a Ph.D. in botany/plant ecology from Rutgers University, and has engineered CPS’ cannabinoid extraction efficiency and tracking programs, developed one of the largest production databases in the United States, and created efficient and repeatable production methods informed by rigorous data collection and statistical model building.

 

you don't think ive read the same thing lol, you need more hands on experience before commenting anymore bud

 

Well, I've been growing since the early 90's, far from the most experienced grower on here of course, but I need more hands on experience in order to quote actual scientific studies or PhD experts on the plant we are discussing? I don't know about that one, nearly 2 decades would seem enough experience to comment on an open cannabis forum.