Black Spots and Dryness of Bottom Leaves HELP

Hey I have run into a problem, the lowest and oldest leaves seem to be dying, getting black or brown spots on them and getting extremely dry, dry enough that when I squeze them they will fall to pieces, while the top leaves look healthy. Im not sure if this is because maybe i had them to close to the lights? Here are some pics, some help would be greatly appreciated. Should i cut these leaves off? HELP!!

your soil looks dry. trim the damaged leaves. ONLY the damaged leaves. the top leaves look good.

First off- don't panic. It's lower leaves, not your growing tip. New growth looks OK.

What is the temp and humidity in the room?

How often are you watering?

What type and power output of light?

Got an oscillating circulation fan?

How are you ventilating the room (exhaust fan? how often does it run?)?

the temp is around 20 degress, but the humidity im not sure off. Im watering it about once a day or sometimes a bit longer if the soil remains moist longer. The 2 side lights are 24w cool white, and the top like is 40w warm spectrum. I have a fan blowing on the plant usually 24/7, and i try to keep my room ventilated just by leaving the window open. Thanks for the help so far.

Growing weed is an exact science. You need exact figures, not guesses, to work out problems. You need a thermometer/hygrometer, preferably a digital type with a memory for high and low values. Very cheap- and an essential tool.

I suspect your problem is related to excess humidity. When you are relying upon opening a door or leaving a window open to ventilate a grow, there's a very good chance it is not being properly ventilated. Excess humidity can cause the sort of leaf damage I'm seeing. Humidity should be around 30-50% for vegging. You can have all the fans you want blowing on the plant, but if it is not fresh air, you're wasting your time.

You're going to get a stretchy, spindly plant which will yield pretty close to nothing unless you get serious and build up a room with some good lighting and ventilation.

From what it LOOKS like, it looks over nuted and definitely dry. I had the same problem and my leaves looked exactly like yours do now. I transplanted them into slow release nute soil and the plant started to thrive and eventually dropped the leaves on its own. Make sure to water AS SOON AS the soil looks (or feels) dry. You can put more then enough water in the pot as long as you have good drainage holes. Good luck!

pauliojr said:

From what it LOOKS like, it looks over nuted and definitely dry.

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I disagree- fert burn usually shows up as yellowing and later dying leaf tips. Not enough yellow in the tips of the pictured plant for it to be fert burn. Looks more like excess humidity.

Al B. Fuct said:

I disagree- fert burn usually shows up as yellowing and later dying leaf tips. Not enough yellow in the tips of the pictured plant for it to be fert burn. Looks more like excess humidity.

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I am going what I have personally experienced. You are correct in saying nute burn has a yellowish and later drying tips, but that is only 1 way. Not thinking in my last grow I had transplanted my babies into starting soil then added the Miracle Grow plant food to them way too early. They were fine until then. Then they all started showing the same discoloration as the pics above a day after the plant food was added. I immediately transplanted my babies into JUST starting soil and within a few days all was fine. Everything was the same (humidity, temp, watering, lighting, etc) I am positive it was because of nute burn and simply just adding nutes to early.

The green colour remaining in the necrotic tissue indicates it died very quickly; that pattern occurs more often from excess humidity.

Nute burns are effectively blockages of the small capillaries in the leaf. This is why they tend to occur first near the leaf tips and margins. The starved tissue takes a couple of days to fully cook- the cholorphyll breaks down in the starved area and the leaf turns yellow.

High humidity prevents proper transpiration from the leaves, which kills tissue more quickly than a nute burn, leaving the green chlorophyll intact in otherwise dead and crispy material.

Extreme overtemp can have a similar effect, drying out the leaf material quickly, before the chlorophyll has had a chance to break down, leaving the necrotic tissue green instead of yellow. Could have been an issue here as well as I'm not sure we know exactly what the temps have been. 20C isn't bad at all, if that's what it was.

thanks for the help guys, well i dont think it could be nute burn because i havent added any nuts at all, and there was none in the soil. Maybe it has something to do with how i was spraying the leaves with water? that could have caused the humidity problem eh? there is about 3 or 4 leaves affected by this, i guess il just cut those off.

treasure_hunter said:

thanks for the help guys, well i dont think it could be nute burn because i havent added any nuts at all, and there was none in the soil. Maybe it has something to do with how i was spraying the leaves with water? that could have caused the humidity problem eh? there is about 3 or 4 leaves affected by this, i guess il just cut those off.

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O.K. I hope everything works out for you. LOL, that is why I capitalized LOOKS LIKE in my first reply. What kind of soil are you using?

Al B. Fuct said:

I disagree- fert burn usually shows up as yellowing and later dying leaf tips. Not enough yellow in the tips of the pictured plant for it to be fert burn. Looks more like excess humidity.

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This also happens when the leaves are exposed to too much heat.

pauliojr said:

O.K. I hope everything works out for you. LOL, that is why I capitalized LOOKS LIKE in my first reply. What kind of soil are you using?

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Im just using a generic potting soil i bought from wal mart for like $2. I think il try to get something a bit better quality next time or when i tranplant it to a new pot.

I have the same on my babies but i have perfect humidity, good ph good soil good drainage good light etc I think it is that the plant is to dry or too hot, or both... mine is not too close to the lights but it has got pretty warm in there and i have left it a while before watering, definetly not nutes as i havent given them any. so with mine i think it may need more watering. as the other babies are perfect and one of them is the same kind. i thought because it was smaller i would give it less water than the rest but...... i think its just thirsty in the heat.
cheers.