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Growing cannabis on coco


A good grow stands or falls on the commitment and thoughtfulness of the grower. This guide is aimed at the growing of skunk and indica varieties, which does not mean to say that other varieties cannot be grown in the same way.

There are two main methods: 1) using coco in pots 2) using coco in mats, or slabs. The advantage of growing in pots is that that you can move your plants around during the grow and harvest. Since one plant grows faster than the other, it is easy to sort the plants on size and so re-arrange their positions to reflect which needs most light, when.

Only if you have an irrigation system is growing on coco mats advantageous, creating less work and waste. This guide only goes into the first method, and only looks at the growing technique (so not establishing the grow space. How you do this is something to ask some expert or grow shop staff member about as there are big variations between different rooms and people).

Read here about the benefits of growing in coco coir

Coco in pots

Coco in potsIn order to keep the grow and harvest time as short as possible and to avoid a number of problems we will use a 4 litre pot (15x15x20 cm). In this, provided we use a Citral, White Widow, or White Widow-relative, we do not need to give any grow time provided the climate for the first two weeks is good and humid. A K2 or a Top-44 for example are slow growers that will need a minimum of 5 days growth.

Since we’re not giving the plants any time to grow then we can expect a maximum 15-gram yield off each plant (average). So per 600 W lamp we need a minimum of 40 plants. Since the artificial light that we’re using is not as strong as the sun, the light intensity reduces the further away from the lamp the plant is. That is why a short plant has long, full flowers from its top to its base, while a taller plant can end up looking a bit empty, especially lower down. A big plant (bigger than 75 cm) does not yield more and is unmanageable.

Ordering and comparing pots

Big advantages to growing in pots are that your plants can be moved and you can see per plant how much water they need or not. Especially in the first 3 weeks there can be big differences between plants and as a consequence the clones with which you began are different. So after 5 days the one plant can have already reached 15 cm in height and already be using a lot of water, while the other is still thin and using barely any water. If then go ahead and water all the plants when not all of them are dry, then you’ll drown the plants that are still small by giving the bigger plants water when they need it.

The big plants therefore grow harder and the small ones even slower and the differences will just become bigger and bigger. The more often you select, the more regularly your plants will grow.

As your harvest advances, you often see plants in the middle becoming yellower than those at the edges. This happens because the plants in the middle receive more light energy, they process their nutrients more quickly and therefore they need more nutrients. If you move such a yellow plant to the side, give her some time to absorb more nutrients and it will become green again. The reverse also applies, namely, a plant that’s green (so a plant with plenty of unprocessed nutrients) under the light can process its nutrients quicker than a plant that is already yellow, because the latter will not be able to transport nutrients fast enough. Moving lamps or shifting the lamps a little in such a situation is the best thing to do.

Determining the grow time and thereby the eventual size of the plant is related to the number of plants per lamp. Try to keep the grow time as short as possible because the shorter the time to harvest the less time there is for small problems to develop into big problems. With Citral and the White varieties you don’t need any grow time and can go straight into the 12-hour phase. If you work with Libra tubs (ready-to-use grow tubs with a single slab of coco of size 100x18cm) then 6 tubs per 600 W lamp with 5 Citral plants per slab is the optimal density. With White varieties, that’s 1 tub with 5 plants and the other with 4 plants since these will grow broader.

Coconut coirK2 and most skunk varieties can usually profit from a minimum of 5 days growth. This is the sort of information you can get from your supplier since varieties from different suppliers can have differences even when the name is the same.

To optimise the light distribution you need to try and hang the lamp as low as possible. To do this, the plants in the middle need to be small and those around the edge large. As is probably clear, you are not as able to move your plants around when growing them on a slab of coco as you can when they’re in pots.  That’s why you need to try and place your seedlings in the first few days of the grow as carefully as you can.Rock wool cube

That proceeds as follows: to give the plants a sturdy base and yet be able to move them around in the first few days, first put the clones in a starting block (or a small coco pot with no base). This is a 7.5x7.5x7.5cm rock wool cube in which the plants make their first new roots. For the duration of the first few days the starting block can still be moved around so that in this phase the plants can still be selected and re-arranged. Take good note of the size of the plant, size of the root system and the speed of development Cannabis rootsover the course of these few days (has it grown a lot or not much?).

Place the big plants around the edge once the roots are starting to grow out from the base of the stating block. The plants that root later will also only later be given a position. Eventually the last and smallest plants can be positioned right under the lamp. Should there turn out after a few weeks to be one big plant right under the lamp in the middle, then you can top it (cut off the main growing tip) so that once again you have a nice even field. As soon as the plants are in their pot or on the coco slab then you can start giving them water using the irrigation system.

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