Categories
BLOG

weed grown in water

How To Water Cannabis Plants: A Comprehensive Guide

Your cannabis plants need water in order to thrive. Seems simple enough, doesn’t it? But did you know that incorrect watering is the most common reason for plant health issues? Learn how and when to water your plants so you can avoid any problems before they have a chance to happen!

Contents:

Watering cannabis plants seems like the easiest thing to do, yet many growers, especially those new to cannabis cultivation, make mistakes with watering. Overwatering is one of the most common reasons for all sorts of growing troubles such as nutrient deficiencies and cannabis diseases, although giving your plants too little water can also negatively affect their growth.

HOW MUCH SHOULD YOU WATER CANNABIS?

One issue with watering plants is that it isn’t really an exact science, and many different factors contribute to how much you should administer. As an obvious example, as your plants get bigger, their watering needs will change. But there are other, more complex variables that also determine how much or little you should drench your plants. Let’s discuss some of the most vital:

STAGE OF GROWTH

Cannabis plants have different watering demands depending on their stage of maturity. The specific guidelines we share below apply to mature vegetating and flowering plants. Seedlings and clones require much less water.

In the early stages, avoid watering your plants with a powerful stream that might knock them over and disturb developing roots. Instead, use a light mister to gently moisten the substrate.

Wait for the soil to dry out completely before repeating the procedure. How quickly the soil will dry will depend on your environmental conditions, but this roughly translates to misting once every 2–3 days.

GROWING MEDIUM

The type of growing medium you use largely determines how much water the soil can hold, and drainage plays a huge role in how often/how much you water your plants. Cannabis likes rich yet airy and “fluffy” types of soils that are well-draining. As another consideration, the growing containers themselves must have holes punctured in the bottom to allow the water to escape. More compact soil mixes will hold moisture much longer, so they require less frequent watering as a result. Otherwise, moisture can linger in the soil for some time, which can lead to nutrient deficiencies, root rot and fungus, pests, and a whole lot of other problems.

Here is a quick way to check if your water is draining properly: If it takes several minutes for water to drain after drenching the soil, and/or if it takes longer than 3–4 days for your soil to dry out, it’s likely that you have a drainage issue. Even if you don’t see adverse symptoms now, it could definitely lead to more problems down the line. In this case, you can add perlite or something similar to your soil to aerate the mix and improve its drainage ability. Perlite ensures that water doesn’t stay too long in your pot. The key to good soil for cannabis plants, whether store-bought or homemade, is to balance moisture retention with water drainage. This usually means soil that is dark and rich, but amended with perlite and/or other substances to promote a healthy and efficient medium for plants to grow.

SIZE OF CONTAINER

Then of course, the dimensions of your container will also affect the overall balance between moisture retention and drainage. If you have a tiny plant in a huge pot, drenching the whole substrate is going to drown the poor thing before it gets a chance to flourish. Similarly, you might experience the opposite issue with huge root-bound plants stuck in minuscule pots. This is also the reason that growers normally start seedlings in smaller pots, then up-pot them later as the plant grows. A small seedling pot makes it much easier not to overwater the sensitive seedling.

OUTSIDE TEMPS AND LIGHT INTENSITY

Cannabis plants don’t always grow at the same pace. A plant in a cooler environment, for example, will grow much slower than one under balmier conditions. Light intensity plays another big role here. Plants that receive more heat and light are bound to have higher water and nutrient requirements than those with meagre light and chilly temps.

HEALTH OF CANNABIS PLANTS

The general health and vitality of your plants will also determine how much water they require. If growth is slow or stunted, or if a plant is afflicted with diseases or pests, it will likely not need as much water as one that is thriving.

HOW TO TELL IF YOUR PLANTS ARE THIRSTY

You now know about the factors that determine how much and how often cannabis plants need water, and how these factors can be different for everyone. So now, how can you tell exactly when you should water?

Here are some signs that your cannabis plants are thirsty:

DROOPING, WEAK PLANTS

If your cannabis plants are very thirsty, they will droop. The whole plant will appear rather sickly and lifeless, so it’s difficult to overlook this sign. One catch here though is that thirsty plants can look very similar to those that are drooping because of overwatering. The difference here is that the leaves of overwatered plants are usually dark green and form a “claw” where they curl and bend downwards, so the whole plant takes on a heavy and waterlogged appearance.

If you’re somewhat experienced, you should be able to tell these conditions apart. Most of the time, it should be obvious if the drooping is from over or under-watering: If the soil is bone-dry and you know you haven’t watered in quite some time, the sickly appearance of your plants is less likely from overwatering.

Tip: Know that slightly underwatering your plants is always better than overwatering. If you water thirsty, otherwise healthy plants, they should normally recover their appearance in a couple of hours. Occasional underwatering doesn’t usually have harmful consequences. Overwatering, on the other hand, is a silent killer.

YELLOW OR BROWN LEAVES

Along with your thirsty plant wilting and drooping due to a lack of water, it may also display discoloured leaves in shades of yellow and brown. While it is perfectly normal for plants to develop yellow leaves during the final weeks of bloom, a healthy vegetating plant shouldn’t have any/many dry, yellow, or brown foliage.

JUST CHECK THE SOIL!

Take the guesswork out of your watering routine with a simple method. Placing the tip of your finger into the top 5cm of soil provides a good indicator of how dry the upper soil has become. However, it won’t allow you to detect the water content of the middle and bottom of the growing medium.

Weighing your pots instead will give you a clear picture of how much water remains. You can operate based on a general feeling of how your containers feel in your hands when they are dry compared to when they are saturated. Even better, weigh them to know exactly when they’re ready for some more H₂O.

HOW TO WATER YOUR CANNABIS PLANTS

Here is a simple rule: Water less, but water well! Rather than giving your plants a little bit of water often, treat them to a healthy, less frequent soak. But how much water is sufficient?

A good soak means watering the medium to 25–33% of the pot capacity. This amount of water will provide the root system with all it needs, without causing pooling and potential fungal issues.

When watering, aim for the middle of the substrate first. After letting the roots breathe, water the edges of the container too. This approach will encourage the root ball to reach to the edges of the pot, and also shuttle nutrients sitting in the top of the medium down to the root system below.

This method will deliver the correct amount of water, without creating pools in the substrate. Excess water creates a humid environment—a perfect breeding ground for fungal pathogens that lead to root rot.

DON’T LEAVE YOUR PLANTS SITTING IN RUNOFF

Along with your containers featuring holes at the bottom for water to escape from, the containers themselves should be lifted slightly off the ground so that all the water can drain and plants aren’t sitting in stale liquid. Drainage trays can catch this runoff, but should immediately be dumped after collection to avoid creating a breeding ground for bacteria, pests, and mould.

THE IMPORTANCE OF PH WHEN WATERING PLANTS

If you are growing cannabis organically in soil, you shouldn’t need to worry much about the pH level of your water/nutrient solution. But for the majority of cannabis growers who are using common mineral nutrients and grow weed in soil, coco, or hydroponically, the correct pH level of the water is very important.

The reason for this is that cannabis plants have a limited pH window where they are able to take in nutrients. If the pH level of the water is either too high or too low, the plants are unable to take in nutrients even if they are present, a phenomenon known as nutrient lockout.

When you grow in soil, the pH range of your water should be 6.3–6.8. If you grow soilless (e.g. coco) or hydroponically, the pH level needs to be even lower, 5.5–6.1. To test your water pH, use a pH measuring stick or pH measuring drops. If the pH is too high or too low, use some drops of “pH down” or “pH up” to adjust your water to the right level. Most of the time, if you’re using tap water, your pH will likely be too high.

Also, if you’re adding cannabis nutrients to your water, measure the pH after each feed. This will give you accurate data of how you have influenced the soil. It will also let you know if you need to add more nutes, or modify the dose during next feed.

BOTTOM LINE—WATER WELL, BUT NOT TOO OFTEN!

If you know how and when to water your plants, and are aware of any associated issues along the way, you can prevent most common cannabis growing problems. You will raise happy, healthy plants, and can look forward to fantastic yields!

The HI-98107 pHep pH tester provides fast and accurate pH readings. The easy-to-use device is designed for non-technical users, and can help both novice and advanced growers measure water pH.

HI-98107 pHep pH tester provides fast and accurate pH readings. The easy-to-use device is designed for non-technical users, and can help both novice and advanced growers measure water pH.

Click here to find out everything you need to know about how and when to water cannabis plants. Watering may seem easy, but many growers still get it wrong.

How Often Do I Water Indoor Marijuana Plants?

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 indoors, and knowing how to water your plants will save you a lot of frustration!

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.

  • Soil – Water plants when the soil feels dry up to your first knuckle (or if the pot feels light).
  • Coco Coir – Aim to water plants every 1-2 days. If coco is staying wet for 3+ days, try giving less water at a time until plants get bigger and start drinking more. Don’t wait for your coco coir to dry out, but don’t water if the top inch feels “wet”. If the container feels light, it’s definitely time to water!

How to water cannabis properly (when using a well-draining potting mixture with liquid nutrients)…

In soil, wait until the topsoil feels 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).

In coco coir, you want to water every 1-2 days if possible and adjust the amount of water you give accordingly. The top inch doesn’t need to completely dry out between waterings.

If you’re regularly adding nutrients in the water, give enough water each time that you get 10-20% extra runoff water drain out the bottom of your pot. This prevents a buildup in the potting mixture because otherwise, you are continuously adding more nutrients to the system.

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) or need to give less water at a time. If your plants are very small compared to the container they’re in, give water more sparingly until plants get bigger.

Growing in Super Soil?

  • If you’re growing in super soil or another heavily amended potting mix, you may not need to add extra nutrients to the water because your plants can get all their nutrients directly from the soil.
  • Any time you’re not adding extra nutrients in the water, you want to avoid getting runoff water because it 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 try to give just enough water that you wet the entire medium but don’t get extra water coming out the bottom.

Some growers swear by 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 .

How to Provide the Water

When I first started growing, I gave my plants water using a watering can. A watering can works great, but it’s hard to water a bunch of plants with one watering can because you have to keep filling it up.

An old-fashioned watering can will get the job done, but they typically don’t hold a lot of water at a time, which is inconvenient if you’re growing a lot of plants

I personally like using a Battery Operated Liquid Transfer Pump to water the plants. You can pump water from a bigger container to your plants. This is a 3-gallon water container from Wal-Mart, and the pump just reaches the bottom.

My grow tent is 2 feet deep and this reaches the plants in the back. However, I don’t think the tube is long enough to reach the back if your space is deeper than that.

Some growers set up elaborate drip feeds to pump water if they have a lot of plants they can’t easily reach, both homemade or pre-made.

Let us know if there’s something we missed. Growers get creative!

How to Collect Runoff Water

It’s important to keep plants on saucers or trays so you can remove the runoff water. You can collect the saucers one by one and dump them out, but that also gets inconvenient with many plants.

It’s inconvenient to empty saucers one by one if you have a bunch of plants, but you don’t want to leave plants sitting in runoff water

If you put your plant on plastic trays, and then put the trays on a slight incline by putting something small underneath in the back, it will catch all the runoff water and cause it to drain to the front. The item in the back only needs to be about half an inch thick, for example a piece of plywood. However, if you can find something more water-resistant, like plastic, that’s even better.

These 1’x2′ plastic plant trays work well if they fit your space. You can fit four of them in a 2’x4′ grow tent (this is the grow tent I use) with up to two plants each as long as your plant containers are 11″ wide or smaller at the base.

Put trays on a slight incline by placing something underneath the tray in the back. This causes all the water to come to the front for easier collection. Each of these trays has a small plastic board (which we found around the house from something else) under the back. Anything that’s about half an inch high will do the trick. These particular trays accommodate plant containers up to 11″ wide at the base.

Not sure how to remove runoff water after watering your marijuana? Wet vacuums can be a great choice, especially if you already have one in the house. I didn’t have one, so I got Bucket Head attachment which can turn any standard 5-gallon bucket into a wet vac. You can buy one online but it’s $10-15 cheaper if you get it in person at a Home Depot. Another similar option is the Power Lid, though it’s also a bit pricey.

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…

Make Sure Pots Have Good Drainage

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

  • Never use dirt you find outside. Chances are it does not have the correct properties for vigorous cannabis growth.
  • Mix in extra perlite to loosen the soil and allow water to drain through more easily.
  • Bark or wood chips are not the best choice for growing cannabis plants, even though they’re sometimes recommended to improve drainage in soil for some types of plants. On that note, avoid using soil that contains bark or wood chips. What makes soil good or bad for growing cannabis?
  • Use Smart pots – these fabric pots help get oxygen to your roots (which gives you faster growth) and this type of pot makes it 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).

If plants take longer than 3-4 days to dry, make sure your potting mixture has good drainage and consider giving less water at a time

If plants are drying out in 1 day or less, try giving more water at a time or transplanting to a bigger pot

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 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.

That being said, you can plant your seeds right into their final container. Just be careful not to overwater your seedlings at first if they’re in a big container as they’re not drinking much water in the beginning.

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 (if you’re 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.

Different Nutrients for Different Stages of Life

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.

If using nutrients on a regular basis by adding them to your water, it’s generally a good idea to give your cannabis plants nutrients every watering. This ensures the amount of nutrients in the plant root zone is kept relatively stable. If you notice the tips of leaves getting burnt from nutrient burn, it may mean you need to lower your overall strength of nutrients. Most nutrient recommendations on the side of the bottle are too strong for cannabis plants, and should be cut in half unless plants appear pale or lime green (which means they want higher levels of nutrients overall).

If Growing in Composted or Amended Soil, Give Just Enough Water That the Soil is Wet All the Way Through

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 regularly 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 try to avoid a lot of extra runoff if you want your nutrients in the container 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.

Proper watering practices will greatly help reduce the amount of salt buildup and prevent nutrition problems from occurring.

If your cannabis plants shows signs of drooping, often the plant is getting too much or too little water, but not always. Drooping can be caused by….

  • Too much water at a time, or giving water too often
  • Not enough water at a time, or giving water too infrequently
  • Drooping can also occur in hot conditions, or when it’s very humid or dry because the plant isn’t able to move water properly through the plant.
  • Plants sometimes get droopy if they are given a lot of water after being allowed to dry out for too long, due to the stress of the water pressure quickly changing at the roots.
  • Drooping is almost always associated with something going on at the roots, but plants also tend to put their leaves down a bit right before the lights go off, as if they’re preparing to “sleep” for the night. That can sometimes be mistaken as drooping when its actually part of the plant’s natural rhythm.

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 unless you plant is very small for the container). You should be getting 10-20% extra runoff water every time if you’re adding nutrients in the water. In soil, wait to water again until the top inch of the growing medium feels dry, up to your first knuckle or so. In coco coir, aim to water the plants every 1-3 days if possible, and don’t let the top completely dry out between waterings.

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).

Nitrogen Toxicity (“The Claw,” tips bent down, dark leaves)
Learn more about Nitrogen Toxicity

Learn everything you need to know about watering your cannabis plants. No more guessing or worrying!