Seedlings turning yellow and low temp problems

H

Halfrain

420 Member
Hi,
I am new to growing indoors, I have successfully grown out doors before but not for a few years so I’m kinda getting back into it.

The problems I’m having are seedlings that have slow growth and yellow leaves.
It’s winter at the moment and when I first put them in the tent I didn’t realise how cold it was getting (down to 53 degrees) and would come up to 60-65 during the day.
I suspected low temps to be the problem so I tried a few things and ended up going with turning the exhaust off for now until a heater is sorted.
Temps are now sitting at 77-83 with no improvement in growth.
I initially started with the light at the top of the tent about 55” from seedling and also moved it close upon noticing the yellowing hoping it might help with heat and in case they weren’t getting enough light(24”)
The two seedlings on the left are 2 weeks old and the rest are a week and a few days.

Northern lights Auto
24/0 light schedule was 20/4 but wanted to stop temp swings.
Is it in Vegetative or Flowering Stage?
Seedling
Indoor
Soil
no garden soil no added nutrients.
14L
600w HPS was air cooled but plumbed out due to low temps.

Thanks in advance any advice is appreciated.

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Hi @Halfrain - I'm not familiar with that soil, it looks very coarse for a seedling
Think I'd use small doses of organic liquid feed at this stage to get the roots established, it looks like they are struggling
It may be easier in future to start them in light mix or seed & cutting compost to get a good roots before they go into that medium
 
Thanks and no worries, I didn’t really like the look of the soil once I got it home either but all of the seedling mix’s had 3 months added fertiliser and I wasn’t sure how that would good.

I gave them a feed and they look a bit happier.

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Without knowing more about the conditions you are faced with my thoughts are that the yellowing of the seedlings is caused by the "soil" they are growing in.

It is very unlikely that the temperatures are the cause. Think about all the outdoor plants that come up at the beginning of spring or are still growing at the end of autumn. They are very green and the temperatures outside can drop to freezing or slightly below and only warm up into the 40s during the day.

Work on getting the temperature up to something like 78-84 during the day or lights on time and down to the 65-70 range at night or lights off times. At least that is what the temperature ranges should be, or something close to those numbers.

The "soil" does not look like what most would call a growing or seedling soil. To me, what it looks like in the photos is some sort of mix of wood chips and I am not sure that there is any compost or natural soil mixed in. Until those wood chips decompose there is not enough of the nutrients available for the plants to use. If you bought the garden "soil" in a bag then a photo of the front and back would help figure out what it is.

Since the plants perked up it would seem that you are on the right track. For now it looks like you are probably stuck with figuring out a feeding program or schedule while the "soil" situation is figured out. Two different 'figuring out' situations that need to be taken care of at the same time is not easy but can be done.

Halfrain said:
I didn’t really like the look of the soil once I got it home either but all of the seedling mix’s had 3 months added fertiliser and I wasn’t sure how that would good.
Click to expand...
These types of soil mixes are usually not recommended for growing this plant. However this looks like an example of when using them could be what saves the grow and gets the plants healthy and growing properly. If you go that route remember the limitations of the soil and be ready to make adjustments before the 3 month period is up.
 
Personally, I don’t see a too much of a problem with the temp; I grow autos at a pretty consistent 66 degrees. I agree the problem is the soil. I (and many others) use HP Promix - doesn’t have much for nutes, but has a surfactant (makes water “wetter” by breaking the surface tension) and consisting mostly of peak moss has a great texture for seedlings.

The biggest problem as I see it is growing autos - very little time to correct issues, although it can be done - see the link below for an example. I’d just pull the girls and start over with better growing medium. The two-week-old ladies will go into preflower in about a week, and you’ll have a pretty small harvest. Good job on getting some green into the leaves, though.
 
Hey @Halfrain and welcome to the forum!

Please see the comments I made on another thread:

3rd grow going poorly please help

step fathers younger ones on the left my sad looking ones on the right. Same seeds same water and nutes different soil
www.420magazine.com
 
Thanks for your help everyone.
It seems more than likely the soil is the issue.
I’ll see what other soil I can find and pop a couple more.
My first mistake as mentioned above was starting out with Autos thinking it would be a bit easier for my first run. If I had phenos it would have been easier to get the grow room dialed in and not be as concerned about growth.
 
Halfrain said:
It seems more than likely the soil is the issue.
I’ll see what other soil I can find and pop a couple more.
My first mistake as mentioned above was starting out with Autos thinking it would be a bit easier for my first run. If I had phenos it would have been easier to get the grow room dialed in and not be as concerned about growth.
Click to expand...
You mean photos... photoperiod plants. I agree.

For commercial potting soil, a lot of growers use the Fox Farm Ocean Forest or Happy Frog. Both contain worm castings. If you are in the U.S. you can probably find it at ACE Hardware or Home Depot. Happy Frog also contains humic acid, and beneficial fungi and bacteria.

The Fox Farm soils include enough NPK nutrients for about 1 month of growth (?), then you will need to use the Fox Farm liquid fertilizers.

happy growing! 🪴
 
cbdhemp808 said:
You mean photos... photoperiod plants. I agree.

For commercial potting soil, a lot of growers use the Fox Farm Ocean Forest or Happy Frog. Both contain worm castings. If you are in the U.S. you can probably find it at ACE Hardware or Home Depot. Happy Frog also contains humic acid, and beneficial fungi and bacteria.

The Fox Farm soils include enough NPK nutrients for about 1 month of growth (?), then you will need to use the Fox Farm liquid fertilizers.

happy growing! 🪴
Click to expand...
Thank you. The two I had popped into a different soil seem to be going better I have an update below with a couple of new issues.

Update:
Everything seems to be going a lot better since starting new seedlings in different soil.
These 2 seedlings are just over 2 weeks old.
I’ve had a couple issues with these 2 so far it seems they are a bit droppy but also the edges of the leaves are clawing up or turning over. I believe it may have been caused by the HPS light heat when I had the hood disconnect from the fan to bring up temps while I installed a heater. I’m just trying to work out if it’s still a present issue or it’s just damage from before.
I’m thinking it may have been a combination of overwatering and high canopy temps.

I have listed specs below if anyone has advice if the are in the correct range.
Thank you.

Current distance from 600w HPS light that is a sealed hood unit connected to 6” exhaust fan.
18”
Lux- 51000
Room temp - 73.2f 42.2% Humidity
Canopy temp - 86.9f 30.4% Humidity
Root zone temp - 73.4f

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:ciao:
You decided against the Fox Farm soil? What is that soil you are using now? The wood chips don't look composted enough.
 
Halfrain said:
have listed specs below if anyone has advice if the are in the correct range.
Thank you.

Current distance from 600w HPS light that is a sealed hood unit connected to 6” exhaust fan.
18”
Lux- 51000
Room temp - 73.2f 42.2% Humidity
Canopy temp - 86.9f 30.4% Humidity
Root zone temp - 73.4f
Click to expand...
Try moving your light up your humidity is to low to have light that close the air is dry there stressed
 
Halfrain said:
I’m not in the US can’t get a hold of it. I ended up using this:

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Click to expand...
What's in the ingreds? Also, I doubt it has this... NPK numbers?
 
Halfrain said:
I could also lower the room temp to 68-70f if that will increase Humidity and might lower canopy temp just wasn’t sure if I should let room temp get that cold?
Click to expand...
I grow autos indoors at a constant 66-67 degrees F and I get about an ounce per plant. In my context the temp has to be what it is, as I grow in a basement storeroom and I'm too cheap to heat it. It works. My RH is about 50%. I'm not sure the lower temp would work so well with photos. My theory as to why autos can tolerate less-than-ideal temps is that the ruderalis adds a toughness due to its natural growing climate.
 
First, I would not use soil loaded with nutes makes it to hard-to-get control over your feedings second, I would have used smaller pots for seedlings and moved up from there as they got larger. Just my two cents as far as lights I grow outdoors and only use lights for seedlings, I do not have a tent. They will be ok and the ones in new soil will do fine too. Happy growing.
 
MedicalMe said:
I grow autos indoors at a constant 66-67 degrees F and I get about an ounce per plant. In my context the temp has to be what it is, as I grow in a basement storeroom and I'm too cheap to heat it. It works. My RH is about 50%. I'm not sure the lower temp would work so well with photos. My theory as to why autos can tolerate less-than-ideal temps is that the ruderalis adds a toughness due to its natural growing climate.
Click to expand...
Check out my cold brewing tropicanna banana blog (in my sig). I grow photos in the cold every winter
 
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