Starting a Cannabis Grow in Coco

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So, you are starting a cannabis grow in coco. First off, good choice in medium, coco is said to be one of the best mediums you can use to grow cannabis indoors.

This is the first article in a series of guides to get you, step by step, through your grow in coco.

Every angle will be covered, and you will be able to follow the steps to get to a good harvest.

This post is for preparing your medium and getting your seeds or cutting planted. When the seedling grows its first set of true leaves, or the cutting shows new growth, week zero is over. This can take anything from 5 to 15 days, then week 1 begins.

If you have any questions about starting a cannabis grow, then feel free to ask for help in our cannabis growers forum

Preparing Coco for Cannabis Plants

There are many different brands of coco. Some will come in a bag, that is already treated and ready to go into pots. Some will come as a compressed brick, which will expand when you add water.

Coco in a Bag

It is recommended to go with the best quality coco you can get. The most common brand would be “Canna Coco, Professional”


High quality, cleaned and pre-treated coco coir ideal for growing your cannabis plants.

Canna’s Coco Professional Plus is an organic product that has been buffered. This will reduce the side effects of growing in coco, as it could consume some of the nutrients. It is also free of harmful viruses and soil diseases, and provides the ideal conditions for growing cannabis. This coco is highly recommended!

Coco as a Brick

Coco can come in a compact brick form. Water is added and the coco is expanded. This coco can be of a lower quality than coco from a bag, and may need to be treated with calcium and magnesium before using it.

If the coco isn’t treated properly, the cal/mag you feed your plants can be absorbed in it, rather than being used by the plants. You must treat your coco before planting into it.

How Much Coco to Use

The amount of coco you will need will depend on a a few things. How many plants you have, what size pot you intend to grow them in, and what kind of pots you’re going to use. To decide what kind of pot you’re going to use, see our article:

Photoperiod Plants

Start photoperiod plants in small pots, around 0.5L in volume. They will sit in these pots for a week, maybe 2, and then be transplanted into bigger pots.

Generally, starting a cannabis grow in coco is done with small pots around 0.5L in size. A finished cannabis plant grown in coco is usually in around 15-18L pots. Calculate how many plants you are going to grow, and the amount of pot volume you need to fill. Then prepare that coco to be rinsed, and buffered.

Autoflowering Cannabis Plants

Some growers like to start autoflowering cannabis plants off in their final pots. This will reduce overall stress to the plant and increase the final yield.

Some say it is a myth, but everyone has their own way of growing. Either use the method above with transplanting, or start your auto’s off in their final pots of 10-12L.

Buffering Coco

Regardless of which coco you use, you should still rinse it first. Try to remove the small bits of dirt and grit from the medium. This will make it lighter, and more airy, so the root zone can breathe even easier.

Rinsing the Medium

You will rinse away between 10 and 20% of the coco, so calculate how much you need for example, 4 x 0.5L pots, you will need 2L of coco. Plus 10-20%, 2.2L of coco to rinse.

Using a sieve or a colander is ideal, just place the coco into it, and pour water through to remove the smaller particles. This water doesn’t have to be at the correct pH, you are just removing the smaller particles from the medium. The pH will be adjusted later.

Once the coco is clean, place it into the pots and prepare some water with a small amount of nutrients.

Buffering the medium

Prepare some feed for your plants. Do this by getting 3 x your pot volume of water. For example, each plant is in a 0.5L pot, so each plant will need 1.5L of nutrient solution.

If your BG EC is less than 0.6, then add a small amount of nutrients, ( around 1/8th of full dosage) until your EC reads 0.2 points above your BG EC.

Incase your BG EC is higher than 0.6, just add enough nutrients to raise the EC by 0.1 point. You may need to consider reverse osmosis, or using distilled water if your BG EC is too high at this stage.

Once the EC is set, check the pH and ensure it is balanced at 5.8. After that is done, you are all set to pour the nutrient solution through the medium.

This will not only give the seedling something to use when it comes out of the shell, but it puts the pH of the medium in the perfect range for the young seedling.

After your water is poured through all of the pots, and the runoff has stopped, you can plant your seeds.

Planting into Coco

Everything is ready, all you are missing now, is the plants. You should have a seed that is germinated with tap root, or a cutting that has rooted. If you have not germinated a seed yet, then you can read this guide to get you off to the best start:

This should all be done before starting a cannabis grow in coco. Prepare your medium when you have tap root, or a cutting ready for planting.

Planting Seeds into Coco

Simply, make a small hole in the centre of the medium, around 2cm deep. Place the tap root facing downwards, and gently place the seed into the hole. Lightly cover the seed with a little bit of coco.

At this point, it is a good idea to trap in the moisture to raise the humidity around the seed. Use a plastic cup, upside down, or some kind of dome, over the top of the plant. This will prevent the medium drying out too quickly, and the seed, and its root, do not dry out.

Planting Cuttings into Coco

If you have cuttings that have roots, remove some of the coco from the top of the pots, just enough to fit the roots of your cutting a couple of centimetres below the surface.

Spread the roots out as much as possible, and cover them all gently with a layer of coco around 2 cm thick. Do not pat down around it, or try to compress the coco. Make sure the roots of the plant are secure, and then it’s time to put them under lights.

Lighting for Cuttings and Seedlings

Your plants need time to grow roots, and settle into their new medium. They are young, and shouldn’t be pushed too hard with lighting. When starting a cannabis grow in coco, the plant needs a chance to grow enough roots, to convert the light into food effectively. Do not over power them to start with.

The best lighting you can use, would be a T5 fluorescent light, as these give off very little heat, and a nice blue spectrum of light for young plants. T5’s will not push a massive amount of light out, and are very gentle on seedlings and cuttings.

This light is perfect to use for the first week of growth. If you don’t have one that’s fine. You can use an LED or HID light for seedlings too. Just keep the lights at least 2 ft away from the plants until they are ready.

Leave the lights on for at least 18 hours a day. Some growers like to leave the lights on 24 hours a days at this stage. This helps keep the environment level, and there are less temperature fluctuations.

Temperature and Humidity for Young Cannabis Plants

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For the first couple of weeks of growth, your cannabis plants will prefer a high humidity. This will help them eat and drink whilst the roots grow underground.

Keep a light breeze moving around the grow room, especially once the plants have risen above the surface. The breeze will encourage them to build a stronger stem, and reduce the amount the plant will stretch.

Feeding Cannabis Seedlings and Cuttings

Keep the feed as stated above, around 0.2 over your BG EC. You will not have to feed your plants for a few days at least. Though it is good practise to water your plants in coco every day, you need to encourage root growth in these early stages.

NEVER let the pot fully dry out, if you see the top of the medium getting too dry, water the plants. Water around the outside edge of the pots to help encourage the roots to search for the water.

Always get at least 10% run off anytime you feed your plants!

You should only need to feed your plants 2, maybe 3 times in the first week. Always mix fresh feed, and don’t use any food that’s been left for over 24 hours, unless you’re using an airstone.

Final thoughts on Week 0-1

Well, when starting a cannabis grow in coco, nothing much happens in the first week. But this is one of the most exciting times of the whole grow. You can be eager to keep checking the medium for a shoot. Just wait, don’t mess with it, it can take anything from 2-7 days for that seed to pop above the ground.

There is a lot of work being done by your plant under the surface of the medium, you just can’t see it. Growth may seem slow for the first week or 2, but the plants growing quickly, just under ground.

Week 0-1 can last anything from 5 to 15 days, wait until true leaves grow or new growth appears on your clone before moving onto the next week.

So, patience! All you have to do now is wait. Why not join our cannabis growers forum, and talk about your new grow with us? You will get even more help for your grow, and you will get answers to any questions you might have.

For now, this is it, wait for that shoot, and put light over it, feed every couple of days and don’t let the medium dry out. When new growth shows on your cutting, or true leaves start growing on your seedling, move onto week 1.

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