Diagnosis Needed: Leaves Are Shrinking At Tops

Need some help on this RIU veterans.

I've attached some pics of 1 of my two girls. The leaves at the top are extremely small. I am thinking maybe it is a humidity problem because of the close proximity to a 250W HPS. You can see how close they are in one pic. The temps are like 25-28 degrees.

I think you can see some possible nute tip burn.

Can someone please give me some advice and how to proceed.





Also, I'm on week 5 of flowering and they seem to be progressing very slowly. No trichomes present or anything. I suspected a light leak and I made some changes to my cabinet to account for potential leakage. They are AK47 strain.

at 5 weeks flowering id say its heatstress man. need a fan blowing on the tops of plants. need good ventalation and air circulation. hope this helps.

What are you feeding them? It looks like they are deficient in P, mg, and cal. This would be due to low ph making those elements unavailable to the plants. Have you checked the ph? If so what is it?

I just put in a fan that blows upwards at the HPS light and a little at the leaves as well. I will see if this helps and doesn't increase the temperature.

As for nutes, Fertilizer is a solution of potassium nitrate, calcium nitrate, magnesium sulfate, ammonium monophosphate, iron-EDTA and various micronutrients including molybdenum, cobalt, sodium, etc.

I don't have the exact breakdowns on me right now. I am going to measure the pH tomorrow.

Should I do a flush of the soil regardless at this point? I have never done it before.

bump - help needed ^^^

Bump.

Anyone have any ideas what causes leaves to shrink very small, like to the size of a pinky finger?

Don't think it's heat, since I've got the cab to 76 degrees.

brasmith said:

What are you feeding them? It looks like they are deficient in P, mg, and cal. This would be due to low ph making those elements unavailable to the plants. Have you checked the ph? If so what is it?

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Low or high pH, anything out of range will do that. I see the same thing (and am currently battling the same thing).

I see heat stress in them as well. It expresses as slowed growth, canoing or clawing of leaves, new growth is very narrow (reduces surface area), "botched" growth. A fan blowing on them is only going to mean that the warm/hot air is blowing all around them. When using HID you must ventilate, that means exhaust the hot air out, not just blow it around.

If you are absolutely positive it's not heat, then I would next look to transpiration issues, again resolved by ventilation I think. How long has it been at 75F (you were using metric measures earlier, yes?)? The temps you mentioned before shouldn't be bad, but that's assuming you get an air exchange (ventilation?) going.

If you really think the humidity is too high, then make a rice necklace. Take a stocking, put in a little rice, make a knot, put in a little more, work your way up the stocking like that, et voila, rice necklace. The dry rice will absorb a good bit of humidity.

As for the nute burn, yes, you could flush. Or you could just start giving some generous waterings with plain, filtered water (assuming it's at a good pH as well). But, be careful and watch for signs of chlorosis, as that nitrogen is a VERY mobile element.

you need a fan blowing along the tops like the wind does outdoors. peace.

the widowman said:

you need a fan blowing along the tops like the wind does outdoors. peace.

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I have a fan blowing straight up below my HPS light that is near the top sof the plants.

Maybe I will get a more intense fan in there.

Thanks.

Blowing hot air around is not going to cool it off. You must move the hot air OUT. Ventilate.