How Often to Water Coco Coir

by Nebula Haze

Growing cannabis in coco coir is similar to growing in soil, but also a little different. Considering all the opinions about watering out on the internet, it can be difficult to know how to water plants properly. When exactly do you water plants in coco? How much water do you give them at a time? How often should you be giving water to your plants for the best results? This coco watering tutorial for marijuana aims to take the confusion out of all that!

 

How Often to Water Cannabis in Coco Coir

Here are some quick guidelines to help you know how to water your plants perfectly every time.

 

1.) Aim to give water every 1-2 days

Cannabis plants grown in coco tend to do well when they’re getting water every 1-2 days.

2.) Give enough water to always get at least 10-20% runoff water out the bottom

When growing in coco coir, as a grower you need to provide nutrients in the water. However, nutrients can get built up in the coco if you only give just enough water to wet the medium. By ensuring you get a little runoff water each time, you’re helping make sure that any nutrient buildup gets flushed out, so your plants don’t get nutrient burn and are always getting fresh nutrients in the proper ratios.

 

3.) If coco is drying out in less than 1 day even though you’re watering plants thoroughly, you might consider transplanting your plants to a bigger pot.

If your coco is drying out in less than a day, you have a few options. If you don’t mind watering your plant all the time, and it looks healthy, you may not need to do anything. If you’re only getting a little runoff each time, try giving more water at a time. If you water the plant thoroughly, it will tend to stay wet for longer. However, if you’re getting plenty of runoff water and the containers are still drying out too quickly, your best bet is to transplant your plant into a bigger container. With more coco to hold more water, it should dry out much more slowly.

Transplant your plant into a new container by digging a hole the size of the original container, and gently placing your plant in the new hole without disturbing the roots at all if possible, like this!

Transplant seedling from a solo cup into a bigger pot

Pat down the soil gently around the plant and give it a good watering!

 

4.) If coco is taking 3+ days to dry out, give less water at a time until plant starts drinking more

If your coco is taking a long time to dry out between waterings, chances are you are giving your plant more water than it can drink in a reasonable amount of time. Try giving a little less water at a time until your plant is bigger. Once the coco is drying out more quickly, you can up the amount of water you’re giving until you’re getting 10-20% runoff each time.

Small plants in big containers can take a long time to dry out. Until plants get bigger and start drinking more, you may want to give just a small amount of water at a time in a circle around the plant.

Give small plants in big pots only a little water at a time until they get bigger and start drinking more

These seedlings were being watered too often, which is why they’re a little droopy. Young plants don’t need a whole lot of water for the first few weeks.

This seedling has been watered too often for a while, and is a little droopy. The coco still needs more time to dry out before being ready for more water.

This seedling is droopy because it's been given water too often

If you see green stuff growing on the top of your coco (algae) it’s often a sign that you’re watering too often. Although algae won’t hurt your plants directly, it only appears when the top of the coco has been constantly wet for a long time.

If you see green algae growing on your coco, it means you're giving water too often

These plants ended up getting fungus gnats from being watered too often. The first sign of overwatering was all the green algae growing on the top layer of coco.

The green algae on top of this coco is a sign the plant is being watered too often

 

Tips

  • Coco coir is actually pretty forgiving, which is why it can be a good choice for beginners. As long as coco doesn’t dry out completely or get utterly soaked all the time, your cannabis plants will probably be fine.
  • Plants grown in Air Pots or Smart Pots (fabric pots) typically dry out faster and need to be watered more often than plants grown in containers with hard sides.
  • Seedlings drink much less water than bigger plants and may only need a few cups of water at a time at first
  • Plants seem to do better when you avoid letting the coco dry out all the way (as opposed to in soil where plants like to dry out a bit more between waterings). The top of your coco should never appear dusty and dry.
  • On the flip side, don’t water plants so often that the top of the coco is always completely dark and wet. Watering plants too often can cause the symptoms of overwatering and can sometimes attract fungus gnats. It also raises the humidity in the grow space. Higher humidity isn’t a big deal for growers who are starting with dry air, but it can cause problems with mold or bud rot if your environment is getting too humid (above 50% RH).
  • Better too much water than not enough, but try not to go overboard!

 

How to Know When to Give Water Again

It’s time to give water to your plant in coco when….

  1. The color of the coco has begun to lighten from dark brown to medium brown
  2. If you touch the coco, it feels cool instead of moist (if the top of the coco actually feels dry, you should definitely give water)
  3. The container feels light if you try to lift it gently. Plants in coco with lots of water will feel heavy, but plants in dry coco are much easier to pick up.
  4. Consider the “napkin method”
    1. Take a napkin and unfold it so there is only a single ply
    2. Press it gently but firmly on top of the coco.
    3. If you can see the napkin getting wet, give the plants a little more time to dry out.
    4. If the napkin comes back mostly dry, plants need to be watered
  5. Look at these pictures for examples

Pictures of Coco Coir That is Ready to be Watered

If you look at the coco coir in this pictures, you can see it's starting to light up. The plant is ready to be watered.

Example of cannabis in coco coir that's ready to be wateredExample of coco coir that is ready to be watered

This coco coir is too dry! Time for water!

Some growers prefer to water their coco coir every day regardless of how wet the medium is. Coco is a very forgiving growing medium, and it has unique properties that make it really accommodating to roots. For some growers in some setups, this works well, especially in a controlled environment with perfectly sized containers and relatively low humidity in the air. However, for beginners I recommend waiting until the top dries out at least a bit!

Let us know how you water your cannabis plants in coco coir!

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