The Easy Way to Water Plants & Remove Runoff

Published Feb 07, 2021

by Nebula Haze

Watering cannabis plants can be a pain… but only if you don’t know what to do.

Watering a plant may seem simple, but when I first started growing cannabis it actually felt like one of the hardest parts. Seedlings would droop, plants got inexplicable nutrient deficiencies, and I was breaking my back carrying big jugs of water then removing runoff.

Today you’ll learn how to water cannabis plants perfectly with barely any effort

Over the years I figured out how to water plants perfectly with barely any effort. I also learned an important secret: as long as you start with good genetics and create a nice environment, you can skip almost every part of growing besides proper watering and still produce a great harvest with exceptional bud quality. However, your watering system is key to fantastic results.

Today I’ll teach you 3 cannabis watering tactics that maximize growth, increase yields, and improve bud quality while reducing time and effort. Stop worrying about watering so you can pay more attention to your marijuana plants and have more fun.

1.) Set Up So Watering is Easier

Take a few minutes to think about your watering setup. A little forethought and planning can save you a ton of time and effort later.

Make a spot to mix water and nutrients

Set up a table or specific spot to mix up nutrients, check pH, and otherwise prepare water before giving it to your plants. You want a convenient place to hold your water container, bottles, measuring spoons, etc. Being able to reach everything saves time and effort compared to haphazardly mixing nutrients, especially compared to mixing nutrients on the floor (which is weirdly what I did for years).

Set up a table or other convenient spot to store and mix nutrients

Rich airy potting mix

Start with a good soil or coco mix. This not only helps cannabis grow faster but also helps prevent problems like overwatering or underwatering. Most importantly, never use dirt you find outside to grow your plants. Choose potting mixes that appear rich, dark, and fluffy. If your main goal is to water as infrequently as possible, choose soil over coco coir (on average, coco needs to be watered more often than soil).

Choose a rich-yet-fluffy potting mix so plants are harder to overwater (or underwater)

Hands in marijuana "super soil" or living soil

Choose the right nutrients

Mixing up nutrients can take up a lot of time if you’re using multiple bottles or supplements at the same time. If time is of the essence, choose a “just add water” soil (to avoid nutrients altogether) or get an all-in-one nutrient system that gives everything to your plants in one bottle. I’ve had excellent results using Dyna-Gro Grow and Bloom. It can be used in soil, coco, or hydroponic setups. Cheap and easy yet great yields and the resulting buds are top tier.

Directions for Dyna-Gro

  • Use “Grow” bottle in the vegetative stage
  • Use “Bloom” bottle in the flowering stage

How much to give to cannabis plants?

  • Start at 1/2 tsp per gallon. This keeps most cannabis plants healthy and growing fast.
  • Raise amount to 1 tsp per gallon for plants that are heavy feeders. You know a plant needs more nutrients if it’s getting pale or lime green all over, especially if lower leaves are turning yellow and falling off on their own.
  • Drop to 1/4 tsp per gallon if you see dark green leaves or nutrient burn (brown leaf tips), which indicates the plant is getting too high levels of nutrients.

Pretty easy, right?

Dyna-Gro Grow & Bloom works great for growing cannabis in any grow medium including soil, coco, or hydroponics. Use just 1 bottle for the vegetative stage and 1 bottle for the flowering stage at about 1/2 tsp per gallon to give your plants all the nutrients they need from seed to harvest.

Regular pots or specialty pots? What size pot?

There are a few different types of plant containers. Your standard hard-sided container needs to be watered the least often. There are specialty containers that let air in from the sides (for example air pots and fabric pots) which can increase growth rates and reduce the chance of overwatering, but dry out much more quickly and need to be watered frequently.

Choose standard hard-side plant pots to water as infrequently as possible

Air pots and fabric pots result in slightly faster growth but need to be watered more often because they dry the potting mix from the sides.

Blue Thai cannabis plant - choosing the strain you want gives you a lot more control over your final results

While you’re thinking about how often you want to water, also consider the size of the plant pot. If you want to be able to water your plants just once or twice a week, choose bigger plant pots (5+ gallons each). Big containers need to be watered less frequently than smaller ones.

Hard-sided 5-gallon plant pots (often called “nursery” pots) only need to be watered once or twice a week. You can usually find really cheap ones at a local garden center or plant nursery.

Don’t forget to get a matching plant saucer or tray to catch your runoff water!

 

2.) Get the Right Watering Tools

Automatic watering

If you want to avoid watering altogether, there are several options that allow automatic watering. The most common options are clay stakes (which slowly provide water as the substrate dries out) or drip feeders (which are kind of like your own personal sprinkler system to water plants on a schedule). I’ve used the Blumat brand, which offers great options for both. There are also many generic versions of these tools that are cheaper but I haven’t personally tried yet.

One way to automatically water plants is with Blumat clay stakes connected to your water container via a tube

Soak the stakes then stick them right into your plant container

The stakes are connected to tubes that are placed in your water container

Water is automatically pulled from your container as the grow medium dries. Raise the water container to increase the overall wetness, and lower it to reduce the moisture. I use these to keep plants watered every time I need to leave the house for a few days.

The other main automatic watering option is using “drip irrigation” or a “drip feed”. In this setup, water is dripped directly onto the base of plants as opposed through a stake. Kind of like giving each plant their own personal sprinkling system. Once this is set up, all you have to do is refill your main water container and watch plants for signs they need more or less water.

There are many types of drip irrigation systems, from gravity-based versions to elaborate systems that give water to plants on a timer. I’ve also seen many growers build automatic drip-feed systems using pumps and tubes from the sprinkler section of a hardware store. The sky is the limit!

Faucet adapter (connect sink faucet to a garden host)

If you don’t want to lug water back and forth between your water source and grow space, there are adapters you can use to attach a garden hose to your faucet. This lets you add water to a container without having to carry anything.

Get a faucet adapter that lets you connect your sink to a garden hose. This lets you fill up your water container in the grow space without needing to carry water between the sink and your garden.

Blunt tip syringe for measuring nutrients

These can make it easier to quickly and accurately measure out nutrients. Not only can they save time, but they’re also the perfect solution if your nutrient schedule uses metric units and you’ve only got measuring spoons for imperial (US) amounts. I also like to use syringes for certain nutrients (GH Micro I’m looking at you!) that have high “fluidity” (the opposite of high viscosity) which basically means these liquids tend to dribble along the sides of the container instead of pour normally.

These are sometimes labeled as printer refill syringes or glue applicators.

Get 20ml blunt tip syringes for measuring nutrients. The tips are blunted which means they are not sharp. The 20 ml version (sometimes labeled “20 cc”) holds up to 4 tsp. Note: every 5ml (aka 5 cc) is about equal to 1 tsp.

Get the right size water container

I recommend getting a water container that’s easy to use, move, and carry. I personally like 3-gallon water containers because I can carry them much more easily than a 5-gallon, and 3 gallons is usually enough to water my plants once or twice. You may find it more convenient to use multiple 1-gallon containers.

Use water containers that you can safely carry. Don’t hurt your back carrying too-big containers!

5 gallon jugs are often used for refilling reverse osmosis from a water station

If a container feels too heavy to carry comfortably with water, don’t ignore it! Use the suggestions in this section to prevent having to lug water around.

Water transfer pump

A battery-powered water transfer pump can be used to water plants as long as the hose can reach. These allow you to easily pump water from a container to the base of your plants. They’re also super handy for hydroponic growers who need to pump water in and out of their reservoir.

The pump allows you to give water directly at the base of your plants

Watering the plants with a liquid transfer pump

They now offer a version with a long 42″ hose that will reach plants much further away than the older model pictured above.

Get a battery-powered water transfer pump with a 42″ long hose to easily pump water to your plants from a water container. Don’t forget two D batteries.

Inclined trays (or saucers)

If your plant trays or saucers are on a slight incline, runoff water is easy to collect and dispose of since it naturally pools to the front. Additionally, the water will typically flow away from under your plants so they never sit in runoff water even if you forget to remove it. Putting plants on trays makes this easiest, but you can also do it on a smaller scale with big saucers.

First, put your plants on trays to catch runoff water

These plants in trays were put on a slight incline so that water would pool to the front

Put something small and waterproof under each tray in the back to put the trays on a slight incline. I used a cap from a one-gallon water container. As a result, runoff water naturally pools to the front for easy removal. (Go to the next step to learn about convenient ways to remove the runoff water)

What to use to create an incline? Anything small and waterproof works great. Avoid anything too big/tall. Even a tiny amount of incline is enough to move water forward, and too much incline can cause plants to grow off-kilter.

Tools to remove runoff

Here are some options to remove runoff (all these are more effective if you use inclined trays or saucers to cause water to pool to the front).

Wet vacuum – These quickly suck up water for easy disposal. If you are a person who likes to DIY, you may have one of these already. The main downside is they tend to be noisy.

Big Syringe – Since I started using syringes to measure out nutrients, I keep finding new uses for them. Syringes come in all sizes. If I’ve only got a little runoff water to remove, I use a 100ml syringe to quickly collect water and dump it into a nearby container. I have neighbors living below me so I use the syringe at night instead of the loud wet vacuum.

I use a 100ml syringe (pictured here) to remove runoff water. However, if you plan to remove a lot of water at a time they come in 200ml and even 500ml (half a liter!) size with tubing so you can remove a lot more water at a time from further away.

Alternative: Choose “just add water” soil and avoid the need for runoff altogether. Learn more about removing runoff in part 3 of this tutorial.

 

2.) How to Water Cannabis Plants

Seedling watering tips & tricks

Seedlings are super easy to over-water. Use a cup to give just a little water at a time in a circle around the base of your seedling. Learn how to water seedlings in a big pot so they don’t get over-watered. Check out this page with answers and tips for most common seedling problems.

Water seedlings with a few cups of water in a circle around the base of the plant. Seedlings don’t drink much so you don’t want to completely saturate the soil just yet.

How much water at a time

We have a complete “how to water” tutorial but check out this example schedule for watering plants in 5-gallon fabric pot.

  • Day 1 – Give 2 cups (500ml) water per plant
  • Day 3 – Give 2 cups (500ml) water per plant
  • Day 6 – Give 2 cups (500ml) water per plant
  • Day 8 – Give 3 cups (750ml) water per plant (every 3 days after this)
  • Day 11 – Give 3 cups (750ml) water per plant
  • Day 14 – Give 4 cups (1 liter) water per plant
  • Day 17 – Give 4 cups (1 liter) water per plant
  • Day 20 – Give 5 cups (1.25 liter) water per plant
  • Day 23 – Give 6 cups (1.5 liter) water per plant
  • Day 26 – Give 6 cups (1.5 liter) water per plant
  • Day 29 – Give 8 cups or 1/2 gallon (2 liter) water per plant
  • Continue giving 1/2 gallon (2 liters) per plant every 3 days. You may need to give more at a time or more often as plants get bigger. If you’re getting a lot of runoff out the bottom (more than 20%) or plants droop after watering, it means you should be giving less water at a time. If plants get droopy before being watered, you should give more water at a time, or water more often.

Note: This is the schedule that I use for a 5-gallon fabric pot, but your environment will affect how much plants drink. If plants are in hard-sided pots as opposed to fabric pots, you may need to water less often. If you would like to water less often than every 3 days, you’ll need to give more water at a time.

How often to water (tips)

General idea: Water when pots feel light or the top is drying out. Don’t let plants run out of water, but make sure roots get access to plenty of air. If the grow medium is waterlogged and looks super wet, the roots likely aren’t getting enough oxygen for the fastest growth. With over-moist soil, you should give less water at a time or water less often.

Signs of Overwatering/Underwatering

Droopiness is the main sign. Here are examples of leaf symptoms that also commonly appear when plants are over-watered vs under-watered.

This seedling is droopy and getting nutrient deficiencies due to overwatering

Sometimes brown edges can be mistaken for nutrient burn. If you’re seeing the edges turn brown, that may be a sign of overwatering, especially if combined with droopiness.

Example of an underwatered plant. Underwatering is very similar in appearance to overwatering. The main clue is the plant is getting droopy before being watered (not after).

Under-watered cannabis seedling

If you’re seeing droopiness, it almost always means there’s some sort of issue with the roots or watering

Droopy seedling was overwatered in a too-big container, so the roots are having trouble getting the oxygen they need to grow

How to avoid nutrient deficiencies

Nutrient deficiencies can be really hard to pin down at a times. It often has to do with watering habits (and occasionally your environment).

5 ways to prevent nutrient deficiencies:

  1. Avoid over/under watering (this is surprisingly the most common reason for nutrient deficiencies in younger plants)
  2. Give the right nutrients for grow medium (don’t give soil-specific nutrients to plants in hydroponics, etc.)
  3. Check the root pH if you notice spots or discoloration on your leaves
  4. Be aware of light burn, which is often confused for a deficiency
  5. Use the free plant doctor tool whenever you’re stuck!

 

3.) How to Remove Runoff

Removing runoff can be easy. Here are 5 common runoff water strategies.

Pick up plants – Too hard, no need!

No need to pick up your plants if you don’t want to.

Giant syringes – Recommended

Use these syringes (don’t worry, there’s no needle) to suck up runoff water. These are a great choice if you don’t want the noise of a wet vacuum. Make sure to get a convenient container to put your runoff water. Best if you only have a few plants or a little runoff at a time. You probably don’t want to move a ton of water with a syringe.

I use a 100ml syringe (pictured here) to remove runoff water. However, if you plan to remove a lot of water at a time they come in 200ml and even 500ml (half a liter!) size with tubing so you can remove a lot more water at a time from further away.

Wet vacuum – Recommended

With your plants on an incline, you can use a wet vacuum to quickly and easily suck up all runoff water for easy disposal.

A wet vacuum is loud but quickly sucks up water for easy disposal.

Avoid runoff altogether – Monitor carefully

There are a few techniques you can use to avoid ever dealing with runoff water. With these setups, you basically give just enough water to saturate the grow medium to the base of the container, but not enough that extra runoff water comes out the bottom.

Keep in mind when you avoid runoff…

  1. Best when not using nutrients – For example in a “just add water” soil setup.
  2. Can be done with nutrients but requires careful monitoring – Since extra nutrients are not getting washed out every watering, you need to watch plants closely for signs of nutrient buildup. If leaves are getting dark or you see nutrient burn, it means that there is more nutrients in the coco or soil than the plant can use. In that case either lower your nutrient dosage or give plants enough water to cause 10-20% runoff. This flushes out buildup. Don’t forget to remove the runoff water so the nutrients don’t get sucked back up.
  3. Don’t ignore pH – If you’re adding PH Up or PH Down to your water, the pH adjusters can build up in the grow medium just like nutrients. If you’re seeing nutrient deficiencies, one of the first things to check is the pH. One of the easiest things to do is capture a few drops of runoff water and check the pH. If it’s much higher or lower than the pH you’re putting in, you have a problem. Give water with pH at the opposite of the acceptable range until it comes out normal. So for example, if using PH Down, which is an acid, you may notice the pH is too low in the grow medium. In that case, give high pH water within the recommended range. In coco, it’s recommended to keep pH between 5.5-6.5, so if pH is coming out low, give at 6.5 until it normalizes. In soil 6-7 pH is recommended so give at 7 pH if it’s coming out too low.
  4. Pay attention to moisture level at bottom of pot – If you’re not giving runoff, you may not realize if the grow medium is getting fully saturated. At least occasionally, feel the bottom of the pot after watering to make sure it feels moist. If the bottom feels bone dry after watering, chances are you’re not giving enough water at a time. Giving enough water to get runoff will help prevent this issue, but if not giving runoff it’s up to you to monitor the moisture at the bottom of the pot.
  5. Produce runoff when experiencing nutrient problems to help give yourself a blank slate, but typically there is no need to “flush” (give a ton of water at a time).

Some growers try to give an amount of water that saturates the pot but does not result in extra runoff water out the bottom

Watering cannabis with a watering can

Evaporation or drain – Special setup required

It’s possible to remove runoff water via evaporation or down a drain. You should never allow pots to sit in water (this causes nutrient problems, droopiness, and root rot), so allowing runoff to evaporate isn’t a good choice when plants are in saucers.

This is only an effective strategy if the water is running away from pots, for example when trays are on an incline or above a drain. Chances are you will start to see crusty nutrient buildup where the water is evaporating, so it’s recommended to clean the evaporation area on a regular basis to avoid it getting brought back to the plants.

These cannabis plants are growing in a bathtub. No need to worry about runoff water in a setup like this… it goes directly down the drain!

Example of a cannabis Scrog Grow in someone's bathroom - a bathtub can make a surprisingly great place to grow!

 


 

Today you got a crash course in watering your cannabis plants so it’s easy, doesn’t take much time, and gives you the flexibility to have more fun with your plants. Contact us if you have any watering tips you’d like to see added to this tutorial!

 

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