Help with watering seedling in coco

ocean99 · Jan 31, 2025

First time grower here and struggling with overwatering in 70/30 coco/perlite in a 1L pot.

My seedling is day 5 above ground. It hasn't really grown since day 2 and one of the cotyledons has died off. The other is wilting like crazy. I've been told this is due to overwatering - 10-15ml every day. Since then, I let the coco dry out more and it looks slightly better but still stunted. Photo's 1+2 are 2 days ago when the coco was wet. Photo's 3+4 are from today, now dryer, dry to 1-2 knuckle deep.

My question is how much and how often should I water it from now on?

I've done some research and found very conflicting advice. I've seen the following things suggested:

Mist the humidity dome every day, then water with a shot glass worth of water every 3 days around 6" from the stem
Wait until coco is dry 1 knuckle deep and then water
Water 10-15ml every 2 days
Water the coco a small amount around seedling, then leave it and don't water it anymore until the roots reach out the bottom
Water only when the whole pot is nearly bone dry
Weigh 2 x of same size pot with your coco. Water one until it's soaking wet and the other don't water. Water when your grow pot feels the same as the coco pot you didn't water

Which one of these methods is correct (if any)?

Thanks!

Growing details in case they're relevant:
•auto cookies and cream
•70/30 buffed coco/perlite, 1L pot
•humidity dome over the seedling. RH @81%
•120W full spectrum LED light on 50% at 75cm away, around 6000 lux or 150 ppfd, 24/0 schedule atm
•previously been watering every day in a circle around the stem with 10-15ml water. I added calmag and roots nutrients according to manufacturers instructions. pH of water is at 6.2 and EC 400 ish
•temperature normally around 23-26c or 74-78f, but sometimes it does sneak up to 28c or 82f

ArtfulCodger · Jan 31, 2025

I grow in 100% coco, so I'm not sure exactly how the following applies to a 70/30 mix. Here are the things that occur to me as possibilities:

1) I think the humidity dome might be working against you, depending on how high RH you're maintaining. The higher the RH, the slower your plants will transpire, and the slower they'll take up nutes.

2) 60W of LED is a lot of light for brand new babies, especially if transpiration is slow.

3) Unless your coco is full of dust and smalls, I doubt it's an over-watering problem. The flood table under my seedlings runs four times a day.

4) I doubt it's a feeding issue, this early.

Just some ideas. Hope that helps.

ocean99 · Jan 31, 2025

ArtfulCodger said:
I grow in 100% coco, so I'm not sure exactly how the following applies to a 70/30 mix. Here are the things that occur to me as possibilities:

1) I think the humidity dome might be working against you, depending on how high RH you're maintaining. The higher the RH, the slower your plants will transpire, and the slower they'll take up nutes.

2) 60W of LED is a lot of light for brand new babies, especially if transpiration is slow.

3) Unless your coco is full of dust and smalls, I doubt it's an over-watering problem. The flood table under my seedlings runs four times a day.

4) I doubt it's a feeding issue, this early.

Just some ideas. Hope that helps.

1) I've seen everywhere that you need to keep a humidity dome for new seedlings so that's what I did. RH is ~80% with the dome, only ~30% without. Is it actually better to remove the dome?

2) I've also seen 100-300ppfd or 5k-10k lux being recommended for seedlings. My ppfd is at 150 and lux is at 6k. What would you recommend?

3) The coco was brick coco. I did strain and buff it but maybe it's still full of dust since it seems to retain water extremely well, it's only a bit better than normal soil regards moisture retention. I did notice a couple fungus gnats yesterday evening which for me is a sign of overwatering based on my houseplants. In the case of it not being overwatering that's stunting the growth, what do you think is the cause? I'm open to any options, I just want it to grow well

4) I'm not feeding any nutes atm other than a tiny bit of calmag and roots additive, good to know that's a non issue

ArtfulCodger · Jan 31, 2025

The thing to keep in mind is that light, water, and nutes need to balance. You can find a good balance at high levels. You can find a good balance at lower levels. The media will largely dictate what levels are possible, because some media hold less air when watered more. I can't tell you what's right for your situation. I've never run a 70/30 mix, and I've never run your genetics. Anyone who tells you the "right" level of something without the context of the other inputs is guessing. Which isn't to say, for example, that 300 ppfd doesn't work for them...it might work great. It's just that it works in the context of how they water and feed, the media they're using, their environment, and the genetics they're running.

If that was my plant, I'd back off the light and try to keep the humidity around 50%. See how the plant likes it. In a few days, I'd introduce some nutes. Maybe 400 ppm of a balanced synthetic line.

ocean99 · Jan 31, 2025

ArtfulCodger said:
The thing to keep in mind is that light, water, and nutes need to balance. You can find a good balance at high levels. You can find a good balance at lower levels. The media will largely dictate what levels are possible, because some media hold less air when watered more. I can't tell you what's right for your situation. I've never run a 70/30 mix, and I've never run your genetics. Anyone who tells you the "right" level of something without the context of the other inputs is guessing. Which isn't to say, for example, that 300 ppfd doesn't work for them...it might work great. It's just that it works in the context of how they water and feed, the media they're using, their environment, and the genetics they're running.

If that was my plant, I'd back off the light and try to keep the humidity around 50%. See how the plant likes it. In a few days, I'd introduce some nutes. Maybe 400 ppm of a balanced synthetic line.

Yeah I understand that it varies case by case. I am however not sure how to tell if what I'm doing is the right thing.

How much would you back the light off by?

closettrapper217 · Jan 31, 2025

ill tell you from experience i used to run a dome and it kept way too much moisture inside and i was killing seedling over and over. now i just spray them with a couple squirts from a water bottle every day until i start to see some roots and my germination rates have tripled. but everyone has a process

carlosescobar · Jan 31, 2025

plants will often pause for about a week at this stage while its trying to put roots down, I water my pots a few days before i put my seed in and get that soil warm , put my seed in but i wont add any more water , i keep a spray bottle with diluted root juice in just as a mist not to water the soil.

HerbalEdu · Jan 31, 2025

ocean99 said:
I've seen everywhere that you need to keep a humidity dome for new seedlings

first answers when you ask google ...

is humidity dome advised for cannabis seedling

By having so much moisture up top your plant doesn't absorb the required moisture from down below." Unless you are intending to cook your baby, please remove the sweat lodge contraption (humidity dome). Seeds or cannabis does not need enhanced humidity, unless they are cuttings/clones without roots.

Can you use a humidity dome for seedlings?

The humidity dome or artificial greenhouse is mainly used to help seeds germinate and sprout faster. Once your seeds have sprouted you should take them out of the humidity dome. You can also use the dome on cold or windy nights to support young seedlings, or to deter birds from eating your crop before it can grow.

not sure what you call everywhere ...

HerbalEdu · Jan 31, 2025

coco on the two last photo look rather dry, not sure you should let it dry that much ... (soil grower here not coco specialist at all)

ArtfulCodger · Jan 31, 2025

ocean99 said:
Yeah I understand that it varies case by case. I am however not sure how to tell if what I'm doing is the right thing.

How much would you back the light off by?

I'd cut the power by half and see how the plant likes it in a couple days. I know it's not apples-to-apples (for the reasons I ran through above), but I run 50W of T5 for the first month, which is probably equivalent to something like 30W of your LED. And I'd lose the dome.

ocean99 · Jan 31, 2025

closettrapper217 said:
ill tell you from experience i used to run a dome and it kept way too much moisture inside and i was killing seedling over and over. now i just spray them with a couple squirts from a water bottle every day until i start to see some roots and my germination rates have tripled. but everyone has a process

carlosescobar said:
plants will often pause for about a week at this stage while its trying to put roots down, I water my pots a few days before i put my seed in and get that soil warm , put my seed in but i wont add any more water , i keep a spray bottle with diluted root juice in just as a mist not to water the soil.

So essentially the answer to my question about watering habits is to spray, not water, until there's roots, which may take a while?

ocean99 · Jan 31, 2025

ArtfulCodger said:
I'd cut the power by half and see how the plant likes it in a couple days. I know it's not apples-to-apples (for the reasons I ran through above), but I run 50W of T5 for the first month, which is probably equivalent to something like 30W of your LED. And I'd lose the dome.

Light is down to 25%-ish percent, thanks!

ocean99 · Jan 31, 2025

And @ everyone, the humidity dome has been ditched for good

HerbalEdu · Jan 31, 2025

how often to water cannabis seedling in coco

Aim to give water every 1-2 days. Cannabis plants grown in coco tend to grow the fastest when they're getting water every 1-2 days, as long as they're not getting too much water at a time.

The frequency of watering depends on the evaporation and the water supply in the COCO. A common rule is; one daily watering is sufficient during the first few weeks under normal circumstances; then increase up to 2 times a day

One of the biggest issues with coco is watering practices. Coco is a sponge, and like a sponge, when squeezed water comes out, but not all the water. The sponge will remain damp and coco can still appear wet without having enough available water to give to the plant. Constantly watering coco results in over-watering.

HerbalEdu · Jan 31, 2025

ocean99 said:
So essentially the answer to my question about watering habits is to spray, not water, until there's roots, which may take a while?

no you shouldn't spray ... coco need to be watered generously at time, usually with 10% to 30% run off once the plant get big enough

Help with watering seedling in coco

Help with watering seedling in coco

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