Mild droopy and burnt tips late flower

I started noticing mild burnt and curled tips about week 5 of flower, Im currently mid week 7 and noticed the problem has gotten slightly worse. I personally feel that my VPD may be too high as I typically have a leaf offset of anywhere from - 5f- - 2f and currently have noticed it at 0 - +1f giving me the feeling that my stomata have closed up.
Im not sure if I have just overwatered slightly but droopyness gotten worse the day after watering opposed to right afterwards, I think the overwatering may just be a side effect of my stomata closing up due to too high of VPD but I am not sure. I am currently running it between 1.5-1.6 but the problem began week 5 when I began running 1.4+.

The big plant was ahead of the small plant in growth, recently when the problem began the smaller plant took the lead in growth and its leaf offset is still a healthy - 2f - -3f at the sametime as the other is showing +1f.

Smaller plant is further away from the light causing the leaf temp to probably naturally be lower therefore giving it a lower VPD.
First 3 pics are the larger, last 2 being the smaller plant.

Am I right or could there be other cause aside from simply overwatering, when do the plants start typically drinking much less week 5 and later?

Looks good to me I would keep doing what you’re doing some droop some don’t,K.I.S

Look fine to me. Lots of frost even out on a lot of fan leaves probably weighing them down is where the droop is coming from. Those tiny burnt tips are normal.

What strain(s) are they?

Good point

OldMedUser said:

Look fine to me. Lots of frost even out on a lot of fan leaves probably weighing them down is where the droop is coming from. Those tiny burnt tips are normal.

What strain(s) are they?

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Bubba76 (pre-98 bubba x afghani '76)

Thx, so should i continue to push VPD upwards of 1.6? Im running soil (rols) in 15gal. pots I was watering daily in stretch, and every other day after that. It seems I can only water every 3-4 days at this point, is that normal or do you think I overwatered slightly?

16bigfatcolas said:

This guy colas.

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Cola-oscopy

TrentSteel said:

Bubba76 (pre-98 bubba x afghani '76)

Thx, so should i continue to push VPD upwards of 1.6? Im running soil (rols) in 15gal. pots I was watering daily in stretch, and every other day after that. It seems I can only water every 3-4 days at this point, is that normal or do you think I overwatered slightly?

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I would want lower VPD in late flower to help prevent bud rot. I must grow lots smaller plants than you as I use 4gal plastic pots with a low RH like 30% at 75F and would usually only water every 3rd or 4th day when the pots get really light.

I've given up ever getting my VPD even close to what the charts say I should and when I did the cold cement walls and floor in my grow room sweat badly. It's underground like a big concrete bunker and even in late summer the larger area of the basement where the grow room is never gets over 67F. RH in the spare bedroom where a few vegging plants are is only 18% at 75F. Dry like the desert here in northern Alberta. Drier outside at -15C/5F

OldMedUser said:

I would want lower VPD in late flower to help prevent bud rot. I must grow lots smaller plants than you as I use 4gal plastic pots with a low RH like 30% at 75F and would usually only water every 3rd or 4th day when the pots get really light.

I've given up ever getting my VPD even close to what the charts say I should and when I did the cold cement walls and floor in my grow room sweat badly. It's underground like a big concrete bunker and even in late summer the larger area of the basement where the grow room is never gets over 67F. RH in the spare bedroom where a few vegging plants are is only 18% at 75F. Dry like the desert here in northern Alberta. Drier outside at -15C/5F

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How does a higher vpd increase risk of budrot? Because of the dew point and your cold conrete floors? The increased transpiration? Could you explain.

OldMedUser said:

I would want lower VPD in late flower to help prevent bud rot. I must grow lots smaller plants than you as I use 4gal plastic pots with a low RH like 30% at 75F and would usually only water every 3rd or 4th day when the pots get really light.

I've given up ever getting my VPD even close to what the charts say I should and when I did the cold cement walls and floor in my grow room sweat badly. It's underground like a big concrete bunker and even in late summer the larger area of the basement where the grow room is never gets over 67F. RH in the spare bedroom where a few vegging plants are is only 18% at 75F. Dry like the desert here in northern Alberta. Drier outside at -15C/5F

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Im running at 75f, 45%rH, but your running 75f, 30%rH and MY VPD is too high? Thats a little confusing

TrentSteel said:

Im running at 75f, 45%rH, but your running 75f, 30%rH and MY VPD is too high? Thats a little confusing

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45% at 75 is fine. When you said you might go higher you used 1,6VPD as an example and I was too lazy to open up a chart and see what that meant compared to %RH. 50- 60% is generally considered OK as it's high humidity that promotes bud rot. Some guys lose substantial portions of their outdoor crops every year when living in wet and cool areas like the pacific northwest/Vancouver area. I used to live there and the falls are always damp and cool. Can rain for weeks on end and depressing as hell. Constant plugged up lungs and general gloominess. Love it there tho for everything other than the weather. About the only thing to love up here is the dry air and clear lungs. I've been here 22 years and would have needed a lung transplant by now back in BC. Crisp, clean air and barely rains but makes up for it in snow every winter tho a lot less now than 10 years ago. Our fall almost lasted to the very end of Oct and we used to get frost by the end of August.

I just went and filled my humidifier with RO and set the timer 15on, 15off to see if I can't get it up around 40 at least. The plants dry out so damn fast now that the rh has switched to winter levels.

OldMedUser said:

45% at 75 is fine. When you said you might go higher you used 1,6VPD as an example and I was too lazy to open up a chart and see what that meant compared to %RH. 50- 60% is generally considered OK as it's high humidity that promotes bud rot. Some guys lose substantial portions of their outdoor crops every year when living in wet and cool areas like the pacific northwest/Vancouver area. I used to live there and the falls are always damp and cool. Can rain for weeks on end and depressing as hell. Constant plugged up lungs and general gloominess. Love it there tho for everything other than the weather. About the only thing to love up here is the dry air and clear lungs. I've been here 22 years and would have needed a lung transplant by now back in BC. Crisp, clean air and barely rains but makes up for it in snow every winter tho a lot less now than 10 years ago. Our fall almost lasted to the very end of Oct and we used to get frost by the end of August.

I just went and filled my humidifier with RO and set the timer 15on, 15off to see if I can't get it up around 40 at least. The plants dry out so damn fast now that the rh has switched to winter levels.

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Yea but a higher VPD means LOWER rH, its basically the drying power of the air... Moisture does not add to the drying power therefore increasing my rH would only lower my VPD not raise it... Just to clarify to plan to top out at about 1.5-1.6... Ive heard a lot of people reccomend a temp, rH to another person which would only be ideal if the person was running HPS (+2f leaf temps) I imagine that a lot of commercial grows switching to LEDs would have issues dialing things in getting used to those differences in leaf temps.

TrentSteel said:

Yea but a higher VPD means LOWER rH, its basically the drying power of the air... Moisture does not add to the drying power therefore increasing my rH would only lower my VPD not raise it... Just to clarify to plan to top out at about 1.5-1.6... Ive heard a lot of people reccomend a temp, rH to another person which would only be ideal if the person was running HPS (+2f leaf temps) I imagine that a lot of commercial grows switching to LEDs would have issues dialing things in getting used to those differences in leaf temps.

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I've always just gone by %rh/temp so those VPD #s don't compute well.

I only flower under HPS and have for the last 21 years growing up here. Have EYE Hortilux SHPS in 400, 600 and 1000W. Only the 600s are digital ballasts and have 3 of those. Light Rail 4.0 for extra coverage when needed.

Since this pic I added a 600W 10K finishing bulb.

OldMedUser said:

I've always just gone by %rh/temp so those VPD #s don't compute well.

I only flower under HPS and have for the last 21 years growing up here. Have EYE Hortilux SHPS in 400, 600 and 1000W. Only the 600s are digital ballasts and have 3 of those. Light Rail 4.0 for extra coverage when needed.

Since this pic I added a 600W 10K finishing bulb.

View attachment 5223600

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If your running 75f,30%rH with HPS bulbs you must be pushing off the charts like 1.7+, its no wonder you are watering every 3-4 days in small pots. How do your stomata even stay open? Your plants must barley transpire at all. Do you know the average difference between your leaf and ambient temps? I would guess +2f

This is just during ripening phase you run 75f, 30%rH?

TrentSteel said:

If your running 75f,30%rH with HPS bulbs you must be pushing off the charts like 1.7+, its no wonder you are watering every 3-4 days in small pots. How do your stomata even stay open? Your plants must barley transpire at all.

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Barely transpire at all? They drink like fish. The lower the RH the more they transpire. This can also lead to toxic salts buildup when nute levels are high as they pull up extra nutes with the water and over time it builds up in the leaves and fries them. The stomata will start shutting down if the plant is not getting water and goes into drought mode.

I've got a few VPD charts and just found one that uses numbers like you mentioned.

This is one I used before I lost interest.



This one has the type of reference numbers of which you speak.



Right now I'm at 80F and 32 rh so running a VPD of around 2.4 according to the 2nd chart.

OldMedUser said:

Barely transpire at all? They drink like fish. The lower the RH the more they transpire. This can also lead to toxic salts buildup when nute levels are high as they pull up extra nutes with the water and over time it builds up in the leaves and fries them. The stomata will start shutting down if the plant is not getting water and goes into drought mode.

I've got a few VPD charts and just found one that uses numbers like you mentioned.

This is one I used before I lost interest.

View attachment 5223638

This one has the type of reference numbers of which you speak.

View attachment 5223639

Right now I'm at 80F and 32 rh so running a VPD of around 2.4 according to the 2nd chart.

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The higher the VPD the more they transpire UNTIL your VPD gets too high and the stomata close in order to not dry out because of your extremely dry environment. Basically like the belly of an ethiopian child in starvation mode holding every bit of nutrition it can. Your plants afraid its going to dry out in the extremly dry environment so it closes its stomata in order to slow down transpiration and hold water in the soil.

Mild droopy and burnt tips is a sign of high VPD so its funny you say that its normal.

I mean the chart you just referred to says you are in the "danger zone"

Were you referring to the end of flowering where you only water every 3-4 days in 4gal. pots because that is not drinking like a fish, I was watering daily in 15gal. during stretch as I said. I am doing ROLS so I am not letting the soil dry completely.

OldMedUser said:

Barely transpire at all? They drink like fish. The lower the RH the more they transpire. This can also lead to toxic salts buildup when nute levels are high as they pull up extra nutes with the water and over time it builds up in the leaves and fries them. The stomata will start shutting down if the plant is not getting water and goes into drought mode.

I've got a few VPD charts and just found one that uses numbers like you mentioned.

This is one I used before I lost interest.

View attachment 5223638

This one has the type of reference numbers of which you speak.

View attachment 5223639

Right now I'm at 80F and 32 rh so running a VPD of around 2.4 according to the 2nd chart.

Click to expand...

VPD controls growth rates, so Im not too sure why you lost interest after 21 years.

TrentSteel said:

VPD controls growth rates, so Im not too sure why you lost interest after 21 years.

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It's VPD I lost interest in. I didn't know about it until 6 years or so ago and it's just too hard to maintain anything close to what those charts say is the right VPD without running a sealed room that I lost interest in trying. I just set my temp/rh controller a little higher on temp so my exhaust fan rarely kicks on and that helps keep the rh around 40% in the grow room. If there's lots of plants I'll add some CO2 and the plants grow fine. Our tap water from the dugout on the property runs around 800ppm so I need to use RO water in a humidifier and that costs more money until I get around to hooking up my own RO system. Got all the parts over a year ago but haven't felt well enough to spend a day down there mounting everything and hooking it up.

The veg room has no such controls so I'm using a humidifier to keep it up a bit.

OldMedUser said:

It's VPD I lost interest in. I didn't know about it until 6 years or so ago and it's just too hard to maintain anything close to what those charts say is the right VPD without running a sealed room that I lost interest in trying. I just set my temp/rh controller a little higher on temp so my exhaust fan rarely kicks on and that helps keep the rh around 40% in the grow room. If there's lots of plants I'll add some CO2 and the plants grow fine. Our tap water from the dugout on the property runs around 800ppm so I need to use RO water in a humidifier and that costs more money until I get around to hooking up my own RO system. Got all the parts over a year ago but haven't felt well enough to spend a day down there mounting everything and hooking it up.

The veg room has no such controls so I'm using a humidifier to keep it up a bit.

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No doubt, sounds like a struggle to keep the rH up in that dry environment. Pretty sure I would prefer it though, as I prefer the dry winter to any other time of the year, some areas are terrible for PM and bud rot as Ive heard the Pacific Northwest can be.

I also have a tap water running 800ppm+, I dilute RO and dehumidifer water with a bit of spring water to add some trace minerals since Im growing soil. Ive actually been using my tap water just fine in my humidifiers though. I only use RO/distilled in my humidifiers for the hang dry period.
Why do you avoid this is it just the white buildup in your inline fan/charcoal filters or decreased lifespan of your humidifers?

I would definetly use RO in my humidifer if it was feasible but it produces so much waste water.

TrentSteel said:

The higher the VPD the more they transpire UNTIL your VPD gets too high and the stomata close in order to not dry out because of your extremely dry environment. Basically like the belly of an ethiopian child in starvation mode holding every bit of nutrition it can. Your plants afraid its going to dry out in the extremly dry environment so it closes its stomata in order to slow down transpiration and hold water in the soil.

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From what I've researched about it it only does that when there isn't enough water available from the roots otherwise they just drink lots more to compensate and the stomata remain open. Judging from how much extra water they need when my rh is low I'd say the stomata are still wide open.

TrentSteel said:

Mild droopy and burnt tips is a sign of high VPD so its funny you say that its normal.

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Every plant of many different strains I've ever grown ends up with little yellow tips and sometimes they droop and other times they stand up praying to the light. If the edges of the leaves aren't spiking up making them look all jagged then all is well in their world. That's the first sign of heat stress whether from ambient temperature or infrared from the HID lights.

TrentSteel said:

Were you referring to the end of flowering where you only water every 3-4 days in 4gal. pots because that is not drinking like a fish, I was watering daily in 15gal. during stretch as I said. I am doing ROLS so I am not letting the soil dry completely.

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Not just at the end of flowering but all thru late veg and flowering. A 4gal pot seems to be about the size I need so watering is only necessary every 4 days or so. As I use ProMix HP for my base I let the pots get quite light before watering and occasionally they get dry enough so the leaves are drooping but I try to water before that happens.

TrentSteel said:

Why do you avoid this is it just the white buildup in your inline fan/charcoal filters or decreased lifespan of your humidifers?

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The humidifiers plug up in a few weeks if I use tap water. I'll use it in plant trays that I sometimes set on a shelf in the grow room for evaporation. 3 - 10" pans will bring the rh up maybe 15% and with the exhaust fan rarely kicking in I can maintain 30 - 40% in there in the winter. For about 3 months during spring/summer it can stay around 60% most of the time.

I bought a 600cfm charcoal filter about 7 years ago and it's still all sealed up in the box. With no close neighbours I don't really need it but had money to burn at the time and blew 2G at a hydro store. Got the CO2 controller then too but have only used it to see how much CO2 my alcohol burner, candle or even my breath while working in there can produce and decided against investing in a tank of gas. I can keep the CO2 over 1500ppm burning around 100ml of methyl hydrate for every 12 hour shift and only use it during the stretch when the plants are going thru a huge growth spurt and can really use elevated CO2, nutes and light. After the stretch they go back to pre-flower feeding levels and need less inputs to grow well.

Damn, does this girl not look thirsty? Lights out in 5.5 hrs should I water now or leave for the morning, bein watering every other day but not since sunday now. Seemed moist on top this morning but maybe i was just squishing worms with my fingers, lol