by Nebula Haze
“Don’t overwater your seedlings!” is one of the most common pieces of advice for new cannabis growers. Some growers are warned about overwatering, and go too far the other direction and don’t give enough water. But how does a beginner grower tell the difference? Overwatered seedlings look droopy, but underwatered seedlings also look droopy.
Do my droopy seedlings need more or less water? Find out below!
Main Idea: Seedlings just need a little water at a time.
Water in a small circle around the base of seedlings.
Don’t soak the pot, especially a big pot with small seedlings.
Today, learn how to tell the difference between overwatered and underwatered cannabis seedlings.
Step 1: Compare with watering examples
Cannabis seedlings don’t drink a lot of water, but “a lot” can mean different things to different people. Sometimes it helps to get actual measurements so you can compare your watering habits to what’s been working for other growers.
Note: These amounts are for seedlings growing in bigger pots of at least a gallon. Keep reading below for watering seedlings in very small containers. And remember, these aren’t rigid rules. Each plant and setup is a little different, but having ballpark figures can help keep you on track.
Give just 0.4-1 cup (100-250 mL) water to tiny seedlings, then wait a few days.
2-3 cups (500-750 mL) for a seedling this size, then wait a few days.
3-4 cups (750 mL to 1 liter) at this size, then wait a few days.
5-6 cups (1.25-1.5 liters) per plant at this size, then wait a few days.
6-8 cups (1.5-2 liters) water per plant at this size, then wait a few days.
What about in smaller containers?
Solo cup tips
- Plants tend to stay much smaller for longer in solo cups
- Must poke plenty of drainage holes so extra water can drain
- If a cup gets so light it’s easy to knock over, it needs more water.
- If the cup feels heavy or the medium seems soaking wet, wait to water.
Just 1 cup (250 mL) water, then 2 days before watering again.
By this size, slowly give just enough water to get a few drops out the bottom.
By this size in cups, water enough to fully wet the medium. These are 23 days old.
If cups dry out in under 2 days, the plants would love to be transplanted to a bigger container.
By the time plants are this size compared to their pots, start their “adult” watering schedule (below).
How to water adult plants (typically 30+ days old)
- Wait until the top inch of soil is dry (for coco, wait until the top is mostly dry)
- Water until you get 10-20% runoff out the bottom
- Remove runoff (test the pH if needed) and start over
Still not sure if droopy seedlings need more or less water? Look at pictures for clues as to whether you’re looking at overwatered vs underwatered cannabis seedlings.
Step 2: Compare with pictures: overwatered vs underwatered cannabis seedlings
Quick check
- Wet soil + heavy pot + droopy seedling → probably too much water
- Dry soil + light pot + droopy seedling → probably too little water
Look at these pictures if you’re still not sure whether your droopy seedling is getting too much or too little water.
Too Much Water
There are a few ways to “overwater” your seedlings. Too much water (especially over time) can give seedlings “wet feet”, which results in slower growing seedlings that may show deficiencies.
- Too much water at a time
- Watering too often
- No drainage holes to let out excess water
- Grow medium too thick and stays wet a long time (“muddy”)
If the grow medium looks soaking wet, it’s way too much water for a seedling. If the pot feels heavy, that’s another sign it’s full of too much water.
Overwatering picture 1: Classic overwatered cannabis seedling. The grow medium looks wet all over, the leaves droop downwards.
Overwatering picture 2: This cannabis soaked grow medium and droopiness show this seedling is overwatered.
Overwatering picture 3: Overwatered seedlings often show yellow leaves or nutrient deficiencies, especially if the overwatering goes on for a while and the soil never gets a chance to dry out.
Overwatering picture 4: Most cannabis seedling “nutrient deficiencies” are actually caused by overwatering. Notice in the next picture how the soil is soaked throughout the pot. Combined with the brown spots, brown curling tips, and overall yellow color, this seedling displays a clear case of overwatering.
Overwatering picture 5: If the grow medium is so wet that it’s growing green algae on top, you are definitely overwatering.
Overwatering picture 6: When left unchecked, overwatering can cause all kinds of unusual symptoms, like the curling leaves, brown spots, and overall sad appearance of this seedling. But the green algae on the soil of this seedling gives a clear sign the seedling is getting way more water than it can drink.
Too Little Water
It’s less common to “under water” your seedlings, but it happens, especially for beginner growers who are warned over and over not to overwater their seedlings. Underwatering is mainly caused by…
- Not enough water at a time
- Watering too infrequently
- Poor quality soil that doesn’t hold much water
If the grow medium looks bone dry even around the base of the soil, it’s usually not enough. If you pick up the pot, the seedling may feel unusually light, as there is no water inside to give it weight.
Underwatering picture 1: Classic underwatered cannabis seedling. The grow medium looks completely dry, and the seedling looks droopy. Leaves on underwatered seedlings tend to look more thin and limp than the leaves of overwatered seedlings. Chronically underwatered seedlings often appear either pale green like this (or dark green as you’ll see below).
Underwatering picture 2: This seedling has barely grown at all due to lack of water. The leaves are dark and curling. The overly dry grow medium looks pale and dusty from lack of moisture. If you tried to pick up this cup, it would feel as light as a feather.
Underwatering picture 3: A severely underwatered cannabis seedling seems to just wilt as if there’s nothing holding it up. This seedling was growing fine at first but the grower forgot to water it. Seedlings with no water inside often have leaves that appear limp and lifeless. Note: Very high temperatures can cause similar symptoms.
Underwatering picture 4: This cannabis seedling has been thirsting for more water since it germinated. Chronically underwatered seedlings often appear either pale green or dark green. This underwatered seedling is so dark green it looks like it has a nitrogen toxicity, but the real problem is it needs more water.
You should be getting a better idea of what overwatered seedlings look like compared to underwatered seedlings.
But the best way to prevent having to identify which is which is simply to start with good cannabis soil and follow a proven day-by-day seedling watering schedule.
Let’s end this article with a happy seedling that is loving life!
This marijuana seedling is getting the perfect amount of water.
About the Author Nebula Haze
Nebula Haze is the co-founder and main author of GrowWeedEasy.com, which she established in 2010 to make it easier for home growers to produce great quality weed. GrowWeedEasy.com has become a comprehensive online free educational resource for growing cannabis at home.
Located in San Diego, California alongside co-founder Sirius Fourside, Nebula has written hundreds of cannabis cultivation tutorials, grow journals, and guides covering every aspect of indoor home cultivation. Her side-by-side grow experiments and growing tutorials have been featured in publications like Skunk Magazine and Cannabis Business Times.
