How to Grow Marijuana Hydroponically
Last Updated: October 8, 2020 References Approved
This article was co-authored by Lauren Kurtz. Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.
There are 15 references cited in this article, which can be found at the bottom of the page.
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Whether you call it weed, cannabis, pot, marijuana, or something else, the plant known as Cannabis sativa is actually easy to grow at home when you know what you need to do. Growing hydroponically will provide you with higher yields and a shorter grow time compared to growing in soil, but it can often be difficult for the beginning grower to get started with hydroponics. However, most people think of plants growing in water when they think “hydroponics” but actually your plants will get many of the benefits of hydroponics as long as they’re getting their nutrients directly in their water supply. However because of superior air to water ratio in hydroponics, it remains the industry standard. This tutorial will show you step-by-step how to grow your marijuana in 3-4 months using the (arguably) easiest hydroponic method: hand-watering in a soil-less medium.
How to Grow Marijuana Hydroponically. Whether you call it weed, cannabis, pot, marijuana, or something else, the plant known as Cannabis sativa is actually easy to grow at home when you know what you need to do. Growing hydroponically will…
Problem: If your plant is drooping, then it’s usually a sign of either over or under-watering.
Cannabis Underwatering Symptoms
- drooping (plants often get better after being watered)
- leaves often seem “papery” and thin because they don’t have any water inside them. (This is opposed to overwatering where the leaves often feel bloated and “fat” from all the water contained inside)
- chronic underwatering eventually leads to yellowing leaves and nutrient deficiencies
If your soil or soilless medium looks bone dry every time you water, or if you know that your roots have dried out, than skip right down the the solution section, as you definitely have a case of underwatering.
Under-Watered Cannabis Seedlings – Leaves feel papery and thin, growing medium is dry
If it gets worse….
The marijuana plant in the middle is under-watered, causing it to droop. Because it was taller and directly under the grow light, it became underwatered even though it was getting the same amount of water as its siblings. Sometimes you’ll see signs of under-watering immediately after upgrading your grow lights (if you don’t change your watering habits), because all the plants start drinking more due to the extra light and heat.
Chronic Under-Watering (Under-Watering on a Regular Basis)
Most growers tend to give too much – not too little – water to their plants. However, if you’re spending long periods away from your marijuana plants or the containers are drying up in less than a day or two, it may mean that your plant needs to be watered more often, or be given more water at a time.
It’s also common to under-water when plants start overgrowing their pots, or if growers get on a schedule of giving a specific amount of water as opposed to paying attention to the soil.
- plant may need to be watered more often
- plant may need more water at a time
- plant may have overgrown its pot and need to be transplanted
It can be difficult to diagnose chronic underwatering because problems may look like nutrient deficiencies. One big clue is that plants perk up every time after you water.
Chronically Under Watered Seedlings – These yellow leaves are actually caused by the plants being slightly under-watered on a regular basis
The curling/clawing and burnt tips on the following two plants may look like it could be caused by another problem, but in this case the symptoms are the result of the plant being regularly under-watered
Notice how the leaves are clawing and tips appear burnt alomost like nutrient burn. It’s happening because the plant isn’t getting enough water on a regular basis.
The leaves near the buds of this male cannabis plant started turning yellow. In this case, the grower determined it was because the plant had overgrown its pot and was drinking more than expected, and as a result the soil was getting too dry between waterings.
More examples of under-watered cannabis plants
Extreme underwatering on a big plant
Not Sure? If you’re not sure whether your plant needs more or less water, how do you figure out exactly why your plant is drooping?
1.) Determine: Is my plant over-watered?
A cannabis plant does not get over-watered because it’s given too much water at once – overwatering is caused by the plant being watered too often, or if the plant does not have proper drainage (which means the growing medium is taking too long to dry out).
2.) If not over-watered, does my plant have root problems?
Growing hydroponically? When you see signs of wilting and overwatering in a plant that is growing hydroponically with the roots in water, usually that’s a sign of a root problem like root rot.
In fact, all cannabis plants can sometimes display wilting/drooping symptoms that are actually the result of root problems.
3.) You may be seeing symptoms of under-watering
So if you read the short description in step 1 about what causes overwatering (and you’re sure you haven’t overwatered your cannabis plants), and you’re certain you’re not seeing signs of root problems, than your cannabis plant might be drooping or wilting because it needs more water.
If you’ve been underwatering your plant, its leaves will look limp and lifeless, like these plants.
Symptoms of underwatering look the same whether your cannabis plant is growing in soil or a soilless growing medium like coco coir or perlite.
Don’t wait until leaves droop to water your potted cannabis plant! While it is generally a good idea to let your potted cannabis plant dry out a bit after watering (watering too often causes its own problems), you should always water your cannabis plants again before the leaves start drooping.
This is the case for cannabis plants grown in both soilless growing mediums and soil.
First-time growers tend to overwater their plants, but underwatering happens too.
So you’re pretty sure your plant is under-watered. A thirsty cannabis plant will usually perk up quickly after the roots are given water.
Learn about ones of the best ways to properly water your potted cannabis plant every time…
How to water cannabis properly (for soil and most soilless mediums)
Wait Until Plant Needs Water – Wait until the top of the growing medium is dry about a half inch deep (up to your first knuckle). Preventing the topsoil from staying wet for long periods of time can also help prevent bugs like fungus gnats. Some growers prefer the “lift the pot” method to figure out when plants want water, where they actually lift the plant to see if it feels light from lack of water. Some non-soil growers, especially in coco or a very high-drainage growing medium, may water a little earlier when the top is just starting to dry out because it’s more difficult to overwater plants in that type of environment. If you continue running into problems with underwatering, you might consider watering more often than is generally recommended. It may be you need extra watering due to small pot size, rootbound plants, temperature, humidity, etc.
Water until you get a little runoff. If using nutrients in the water, add water until you see 10-20% extra runoff water drain out the bottom of your pot. This helps prevent nutrient buildup in the soil and if you have good drainage this type of watering schedule causes plants to grow faster than if you don’t water to runoff (it also makes it much harder to under-water your plants). If not using added nutrients (plants getting all nutrients from the soil, for example in a super soil setup), then only water until you get just a tiny bit of runoff out the bottom, so you’re not washing out your nutrients. However, you still want to make sure you’re saturating your medium – you don’t want dry spots in the soil!
Go back to step 1. If water does not come out quickly or pots take more than 5 days to dry out for step 1, you may have a drainage problem or need to give less water at a time until your plant is drinking more. If pots are drying out in just 1-2 days, you may need to give more water at a time, or transplant to a bigger pot.
A simple way to tell if a potted plant is ready to be watered is to pick it up and tell if it feels heavy or not.
As plants use up all the water in their pot, it will get lighter. If you need something for comparison, you can get an extra pot and fill it with your growing medium. Now you can use this extra container for comparison with your potted plants as it represents the ‘dry weight’ of your growing medium. If you pick up a potted plant and its feels just slightly heavier than your dry pot, then you know it’s time to water your plant. After a while you get a feel for how heavy your plants need to be and you may not even need the extra pot anymore.
Need more help?
If your plant is experiencing “the claw” and not just normal drooping (the ends of leaves are curling like a claw or pointing down like talons), then you may actually have a nitrogen toxicity (too much nitrogen).
These Plants Are NOT Over or Underwaterd, These Leaves Show Signs of
(“The Claw”, tips bent down, curling / clawing, dark green leaves)
From wilting to dropping to yellow leaves to nutrient deficiencies, under watering cannabis can cause a lot of unexpected problems and symptoms. Learn & fix!