Watering Schedule and Quantity for Cannabis (Grower Discussion)

[johnnyb1984]

It seems that any search on a definitive watering approach is met with ambiguity and vague advice.
ph is important.
Don’t over water.
Don’t underwater.
Don’t water until soil is dry.

But I need some guidance on volume of water at varying stages of growth. Just ballparks. I can adjust according to signs and symptoms. How much once seedlings have emerged? How much getting into a vegging stage? How much at flowering?

I’m growing autos in 3 gallon pots with fox farms soil, but I’m currently in the early seedling stage in small pots before I transplant (I have read that I should plant auto seeds into the final pot, but I had bad luck last time). So, some ballparks on water would be helpful. Some of these watering suggestions talk about runoff from the pot, which suggests at least a gallon of water going through that much soil. But I’ve also been told that I should be measuring water with a dropper at the late seedling stage.

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[Moderator note]

Quick answer: there’s no fixed watering schedule for cannabis plants. Most growers water when the top layer of soil is dry and the pot feels noticeably lighter, rather than on a set number of days.

How much you water depends on plant size—seedlings need small amounts around the root zone, while larger plants need deeper watering that fully wets the soil, followed by a proper dry-back period.

The reason fixed schedules don’t work is because watering depends on factors like pot size, soil, temperature, and plant stage. Smaller plants may need watering every few days, while larger plants in warm environments may need it much more often.

If you want a clearer breakdown of how often and how much to water at each stage, there’s a detailed guide here:
Cannabis watering schedule and quantity (complete guide)

[Spiney_norman]

What you need is an understanding of what cannabis likes. Trying to get an actual number is impossible. A plant will give off more water in warm room with dry humidity conditions and less under wet humid cool days. So we cant say you need to give it a quart every 3 days or such.
Understanding is your key.
OVERWATERING:
Its not giving too much water at one time, Overwatering is keeping the soil wet constantly by watering too often. Cannabis likes wet to dry cycles and after you water the soil thoroughly you want to wait till its nearly all dry before watering again. That might be 5 or 6 days when young and 3, 2, or even 1 day once its bigger. Roots need oxygen to thrive so keeping the soil soaked will kill roots.

WHEN TO WATER:
If you have an empty 3 gallon grow pot you can fill it with dry soil and feel the weight when you lift it. You want the one you have a plant in to be nearly that light. It will feel scary light. If you see the plant wilting all over, not just leaf drooping, then you have gone too long. Just water and remember what that felt like.

RUNOFF:
Not necessary every watering unless you need to test pH or PPMs on the soil because you see the plant having issues.

Thats the basics.

[LearnasUgrow]

The best way to reply to this would be taking a scientific approach. You will want your soil to be about 17 to 22% dryness and moisture compared to its relative dryness that you normally have it as.

Taking this in the consideration, you’ll want a relative moisture content in soil to be 60-70% saturation at base point. You would then take your soil weight at optimum and subtract biomass (relative) to the amount to extract the correct data point you are looking for.

Or…. And it’s a big or……

Just run your own experiments to find what works best for you. Growing doesn’t require years of experience, it requires patience and thought. Do your best with what you have/know.

[johnnyb1984]

Okay. I do understand that it is not an exact science. I guess I should have framed my question a little differently. There are many conflicting pieces of advice regarding how much water should be given during the seedling stage. Mine are about 3 days old now, so should I just simply be missing the dome of my cups, or should I be applying water directly to the soil every 4 to 5 days? I just don’t want to drown my seedlings.

[Brian384]

I’m not an elite grower like most that have commented but when my seedlings come up humidity dome off. I sow in final pot always. Soil or coco. Check vpd and dli. Done. Both similar in germ but watering varies. In soil I can go days without watering. And in soil watering to drought has netted me over 1lb per auto. Consistently. Even crappy auto genetics. When seedlings, and before the month mark with autos in my 6gal pots/autopots I water in soil much less than coco in same 6g pots. You want the seedling to reach for the water so water around the baby lady and remember the larger the pot the more water it’ll hold. So you don’t have to water as much. Even with a huge plant late flower the pot will feel really light and you’ll know. I know your in pre planters so just check weight. Or wait for them to droop a bit. They’re quite resilient plants. I’d rather underwater than overwater. IME it’s easier to nurse back when underwatered. Again just my experiences.

[johnnyb1984]

So, again. How much water are we talking? I told someone I was watering more than just spritzing the plants, and they said I would only need droppers to water until vegging because I was over watering. Is that your experience? Or are you saturating the soil and letting dry for days? I’m not looking for exact numbers. But if I am past the stage of simply spritzing my plants, that’s what I want to know.

[OGIncognito]

Spot on from @Spiney_norman. The seedling stage can be difficult. They need an RH of 65-75% and temps around 76-85. They’ll absorb the moisture from the air in the high RH environment. If you can’t obtain this humidity level mist and place a clear dome over the plant removing daily for re-misting and fresh air. I water about 2-3 shot glasses every 3 days or so

[Audiofreak]

Dont know if this is best practices but it what i do. After veg has started (in soil) i feed /water till i get runoff for testing. I use 7gal fabric pots so it takes about 3 gal to get there. As far as how often…i let her dry a time or 2 till she shows stress (drooping) that lets me know how long she can go. Ill take any advise to improve.

[Spiney_norman]

Seedlings are much more resilient than we give them credit for. I ran an experiment where I place a seed in a solo cup of soil and waited for it to wilt before I watered it.
I soaked the soil and then squeezed out as much water as I could by hand. So it was damp but not sopping wet. The seed was soaked overnight and then placed in the soil with a dome cover. Once it sprouted I left the dome on one day then removed it permanently. Here it is at first…

One week…

Two weeks…

Finally three weeks it wilted.

So I don’t recommend this as a way to treat seedlings. I wanted to find out how fast a seedling will suffer from not being watered. Turns out its quite a long time. It was absolutely fine for two weeks, and even survived the last week though it slowed down in growth. Once I watered it the plant perked up and grew normally.
So bottom line is you can treat the seedling just like the bigger plant. Pick up the container and see if its light or heavy. Even if the top layer of dirt looks dry, if the container has some weight to it then its ok. When it gets light then give it enough water to wet all the dirt again. Give water by pouring it around the edge of the container very slowly so it actually wets the soil and do that until you get a little bit running out the bottom. The let it go until it dries out. My experiment was done to take the fear of the plant dying from no water out of my mind. If a seedling can go 3 weeks without being watered it can certainly survive an extra day if I am unsure if I should water again.
One note I will add,
Those peat pots are not the greatest for cannabis. They wick water from the dirt and dry it out much faster than you want. They don’t break down very fast and you cant really just place them into a bigger pot and have roots grow through the sides. You will have to break up the peat container or remove it before transplanting.
Solo cups are very popular starting containers. Just slice a few spots along the bottom edge for drainage. What I also do is cut the cup along two opposite sides all the way from top to bottom. Then place it into another cup, also with drain holes, so that when I am ready to transplant its just a matter of popping it into a hole made with another solo cup. Looks like this…

You can see how simple this is. No shock to the plant and it takes only a minute.
If you look above at the seedling pics you see it is an a double cup and the inner cup is already split on the sides. From a solo cup I transplant from 14 to 21 days. Depending on when I get the new containers ready is the determining factor. I procrastinate sometimes and that’s the only reason I don’t have a set time. I am pretty lazy.

[Audiofreak]

I dont do runoff untill after transplant. The split cup is a great idea i learned a few grows ago. I do however use a clear cup to start so i can inspect root development before transplant.

[4204life]

My seedlings are in solo cups. I do not use a dome, I will spray around the plant with a water bottle.
Once transplanted to either 2 or 3 gallon bags, they will take almost 1 gallon each every 3 days thru veg and flower.
Hope that helps.

[dbrn32]

@johnnyb1984

There are many conflicting pieces of advice regarding how much water should be given during the seedling stage

Absolutely, and for good reason. The amount of water and frequency of watering will depend on the size of pot, type of media, and environmental conditions. It will never be exactly the same for everyone.

[LearnasUgrow]

@johnnyb1984 , a little misting of the dome combined with 1-2 cap fulls of water from (say a big box store 16-20 oz. water bottle). At about a week I start adding enough water to the media to allow for 3-5% run off (water weight by volume). It’s in my opinion that if, it can not survive after this period, it’s a weaker geno/phenotype.

[Bigcbud]

do you solo cup autos as well?