Grow mediums – Coco Coir

what is coco coir?

Coco coir is an extremely popular growing medium choice, especially for indoor cannabis growers and is thought to be one of the easiest growing mediums to use for marijuana. It is made up from coconut husks and tissue looks a bit like soil when finely grounded, although it does not hold any nutrients. It encourages faster growth, has good amounts of trichoderma, which improves the immune system of plants, controls nutrients well and has great drainage.

Coco coir is light and airy and can produce large plants with bigger yields, although it will need more water than traditional soil. It is also very environmentally friendly and takes longer to break down.

After rinsing, it can usually be used up to three times, unlike peat, which will break down quickly. Pests and bugs do not like coco coir as much as other mediums too, which means you are less likely to worry about plant damage from little creatures. 

coco coir pith
Coco Coir Pith - (CC BY 2.0)

types of coco coir

You can buy coco coir either pre-hydrated or as a condensed brick (and hydrate it yourself by soaking in water). There are also three main types to choose from (pith, fibre, or chips).

Coco Pith is probably the best type for growing cannabis and feels a lot like soil. It is light, with a lovely rich brown colour and allows a lot of oxygen into the mix. Adding a little perlite (20-30%) will help with growth.

Coco Fibre will allow oxygen to enter through the roots and has a more stringy-like texture. If the water is drain too fast, then you can add some coco pith to increase water retention.

Coco chips are very chunky, creating large amounts of air pocket and are not really a good choice for marijuana growers. 

adding nutrients to your coco coir

Coco coir does not come with many nutrients so you will need to add them in yourself. It does already have levels of potassium and phosphorus, so you will need to make sure you do not add to much extra and over do it. Avoid cheap coco coir as these mixes can have high levels of sodium or chlorine which is not good for your plants. 

coco coir- Young_cannabis_plant_in_the_vegetative_stage_01
Cannabis plant growing in coco coir - (CC BY-SA 4.0)

watering with coco coir

As coco coir does not have too many nutrients already added, when watering it is important to add extra nutrients. Combining water with nutrients is also know as fertigation.

When watering with coco coir, you must make sure that the whole medium is covered with water and that some of the water is running off. This helps prevent salt build up, which can damage your plant. Around 20% of the water should be running off your plant. The coco coir should stay moist all the time.

Watering should not ne through a constant drip, but it should be frequent. The growing medium should no look dry and should still be most from the last watering. If it does look dry or is turning a light brown colour, then start watering more.

If you are used to soil growing, this could feel like you are overwatering, but follow the steps above and you should be doing it correctly. Water once or twice a day during the first phase and increase this to 3 to 5 times a day during the flowering period.