by Nebula Haze
If you’re growing marijuana in soil or another growing medium like coco coir, you will have to hand-water your plants. Watering is an important part of growing cannabis, and knowing how to water your plants will save you a lot of frustration!
But how often do you give your cannabis water?
Well, you will want to water your marijuana whenever the top of the soil or growing medium starts to feel dry. I like to water when the medium feel dry up to my first knuckle, or about an inch.
Water plants when soil feels dry up to your first knuckle
How to water cannabis properly (when using a well-draining mixture with liquid nutrients)…
Wait until the top of the growing medium is dry about an inch deep (up to your first knuckle – just use your finger to poke a hole in the soil and see if it feels dry).
Add water until you see 10-20% extra runoff water drain out the bottom of your pot. Go back to step 1. Note: If water takes a long time to come out the bottom, or if pots take longer than 5 days to dry out before the next watering, you may actually have a problem with drainage (more info below).
Growing in Super Soil?
- If you’re growing in super soil or another heavily amended potting mix, you won’t be adding extra nutrients to the water during your grow. As a result, your plants will have to get all their nutrients directly from the soil.
- In that case, you want to avoid giving enough water that you get runoff, because runoff water will carry away some of the nutrients in the soil.
- Watering until you get runoff is important when using liquid nutrients because it helps prevent nutrient build up, but with super soil it’s better to give just enough water that you wet the entire medium but don’t get extra water coming out the bottom.
Some growers also use the “lift the pot” method to decide when to water your plants (basically wait until your pot feels “light” since the plants have used up all the water). It’s up to you to decide what’s easier for you.
I usually water my cannabis with a 1-gallon water jug for small grows, or 5-gallon jugs for larger ones. Runoff water is collected in the trays and after a few minutes I suck it all up with a small wet vac.
Not sure how to remove runoff water after watering your marijuana? I use a Bucket Head attachment which can be turned into a wet vac by hooking it up to any standard 5-gallon bucket. You can buy one online but it’s $10-15 cheaper if you get it in person at a Home Depot!
A downside to the Bucket Head is it’s a little loud, just like most wet vacs. Luckily you only need to use it for a few minutes after watering your plants!
Removing runoff water is a great start to make sure you are watering your cannabis plants perfectly, but it’s also important to…
It’s very important to make sure that water can drain freely from the bottom of the pot, otherwise, the plant can get waterlogged and become overwatered (causing the plant to droop).
In addition to making sure the actual container has drainage (holes on the bottom, or some other way for extra water to escape), it’s also important to make sure your growing medium drains freely. If it takes several minutes for the water to come out the bottom of your pot when you water, it means that there isn’t enough drainage in the actual growing medium (it’s too dense, so water is having a hard time getting through).
How to improve the drainage of your growing medium
- Mix in extra perlite to loosen the soil and allow water to drain through more easily.
- Never add bark or wood chips! They are not good for growing cannabis plants. On that note, never use soil for growing cannabis that contains bark or wood chips. If growing cannabis in soil, the best soil to start with is composted super soil.
- Use Smart pots – these fabric pots help get oxygen to your roots (which gives you faster growth) and this type of pot makes it much, much harder to overwater your plants. A cannabis plant growing in a tan fabric smart pot is pictured to the right.
This is an example of great soil for growing for cannabis – rich, composted, and well-draining
Composted super soil lets you grow organic marijuana without any extra fertilizers or nutrients
Watering Too Often? Barely at All?
In the beginning of your grow, you will likely be watering your marijuana plants every couple of days. Watering every 2-3 days is optimal for a young plant. If it’s taking too long for your plant to dry out, you may need to give less water at a time until the plant is growing faster.
If you feel like you are watering your plants too often, you may need to give more water at a time. You can also move plants into a bigger pot (which holds water for longer).
Bigger pots = water less often
Smaller pots = water more often
Speaking of pot size, it is generally best to start young cannabis plants in relatively small containers (like a solo cup with a few holes cut out of the bottom for drainage), and only move plants into bigger containers as they get bigger.
Starting in smaller containers makes it a lot harder to overwater your plants when they’re young, and makes it easier to flush plants and/or respond to problems if they occur.
If you started your plants in a solo cup, I’d recommend moving to a bigger pot once the plant is a week or two old, as soon as the leaves reach the edges of the solo cup.
10-20% Extra Runoff Every Time You Water (unless you’re not providing nutrients in the water)
Every time you water your plants, make sure that you provide enough water to get about 10-20% extra run-off out the bottom of the container, especially if you’re feeding additional nutrients in the water.
Sometimes soil and soilless growing mediums like coco coir start to collect natural salts from fertilizers that never get washed out.
These built-up salts can eventually cause nutrient problems, pH problems, and nutrient lock-out if they’re not removed on a regular basis.
Making sure you keep adding water until you get run-off is also a great way to make sure that your plants are draining properly.
Plus, this practice will immediately alert you to any drainage problems, (as mentioned earlier, cannabis likes well-draining soil) because you’ll be able to notice if the water takes a long time to come out the bottom, or doesn’t come out at all.
If You’re Not Providing Nutrients in the Water, Only Water Until Just Before Runoff
When growing in composted and amended soil, the soil itself is made to slowly provide nutrients to your plant throughout its life. However, if you’re constantly watering until you get a significant amount of runoff, you’ll also be washing away some of your nutrients.
This is good when the plant is getting the nutrients directly in the water, to avoid unwanted buildup in the soil, but it’s a good idea to avoid a lot of extra runoff if you want your nutrients to last until harvest.
Therefore, when growing in amended soil you should only water until you get just a drop or two of water runoff out the bottom. You want to ensure you gave enough water to reach the bottom of the pot without letting a significant amount of water run out the bottom.
Learn more about growing in composted and amended soil (just add water!)
If You’re Providing Extra Nutrients In The Water…
First, make sure you’re using proper cannabis nutrients for your growing medium. They should be formulated for a plant like tomatoes, and they should have a different feeding schedule for the Vegetative (Grow) and Flowering (Bloom) stage.
It’s generally a good idea to feed your cannabis plants with nutrients every other watering (at most) and provide plain, pH’ed water the rest of the time.
This will greatly help reduce the amount of salt buildup and prevent nutrition problems from occuring.
If your cannabis plants shows signs of drooping, chances are you are over or under-watering.
In order to prevent over or under-watering, make sure you water thoroughly every time (don’t just water a tiny spot in the middle of the pot, you should be getting 20-30% extra runoff water every time), and wait to water again until the top inch of the growing medium feels dry, up to your first knuckle or so.
Underwatered Marijuana Plants
- Wilting is the first sign of underwaterd marijuana plants
- Leaves are limp and lifeless, they may seem dry or even “crispy”
- Will eventually lead to plant death if not corrected
Overwatered Marijuana Plants
- Drooping / Curling is the first sign of overwaterd marijuana plants
- Leaves are firm and curled down all the way from the stem to the leaf
- Will eventually lead to leaf yellowing and other signs of nutrient problems if not corrected
If your plant is experiencing “the claw” and not just normal drooping (like the ends of leaves are just pointing down like talons, then you may actually have a nitrogen toxicity (too much nitrogen).