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My Guide for growing on coco
Growing cannabis is a hobby that more and more people pursue. Everybody can have great
results if you adopt a professional attitude as grower. A good crop depends on the
commitment and cleverness of the caretaker.
This guide focuses on the growth of skunk and indica kinds, varying from 7 to 10 weeks
There are various methods to grow professionally, but we have found that this is the
simplest method to yield results over the gram/watt. We know from experience that if
the beginner is serious and meticulous and visits the shop once every two weeks for
half an hour to catch up the first harvest will yield premium quality and premium production.
Failed harvests due to mistakes in the growing method are rare, but are caused by, for example,
unreliable equipment, low-quality products, nonchalance, and by insect plagues.
There are two differences:
- Coco in pots
- Coco in slabs
The advantage of growing in pots is that you can move the plants during the harvest.
Since one plant grows faster than the next it is easy to sort them according to length
and order them in such a way that they catch as much light as possible. Coco slabs only
offer advantages such as less work (primarily in larger areas) and less waste, and even
higher yields if you use a water system. This guide only discusses the first method. For
growing on slabs, go to 38. Growside Maastricht V.O.F… We only explain the method
of growing and not the layout of the room. Visit the shop for advice on how to do this,
because the layout requires special attention, for example isolation, ventilation and
Coco in pots
In order to reduce the harvest time as much as possible to prevent the development of
problems we use a 4-litre pot of lxbxh is 15x15x20cm. Citral, Peacemaker, White Widow,
Snowball, Santa Maria or other white weeds barely need to be given growing time
(18 hours light or more) if the climate is really damp the first two weeks. A K2 or a
Top-44 for example, are slow growers that can take at least five days of growth.
Since the plants do not or barely get the time to grow, they will yield a maximum of
25 grams on average. That means that at least 24 plants must be placed under every
600w lamp in order to yield 600 grams per 600 watt HPS lamp. Because the artificial
light is less powerful than the sun the intensity of light greatly decreases if the
distance between lamp and plant becomes a bit bigger. For that reason a short plant
usually has long full flowers from top to bottom and a long plant may look deserted
of flowers especially at the bottom. A larger plant (larger than 75cm) does not yield
more than a smaller one and is unmanageable.
Ordering and comparing pots
A big advantage of growing with pots is that you can move the plants and can look per
plant if it needs water or not. Especially the first three weeks there can be large
differences between the plants, which are caused as follows:
The cuttings you start with are different. It is possible that one has grown 15 cm after
5 days and has already used a lot of water while another is still as small and damp as in
the beginning. If you water all plants while some of them are still wet you drown the plants
that were already small while the cuttings that are big get watered at the correct moment.
The large plants will grow even harder and the small ones even slower and the differences
will keep getting bigger and bigger. For that reason you should only water plants that are
The more often you select, the more evenly your plants grow. When your harvest progresses
you often see that the plants become more yellow in the centre than at the side, because
the plants in the centre receive more light energy and process the food more quickly and
therefore use more food. If you put a yellow plant on the outside you give it some time
to take in food and become greener again. This means that a plant that is green
(a plant with much unprocessed food) processes more food under the light than a plant
that is already yellow because it cannot supply the food quickly enough.
Moving lamps or moving the lamps somewhat is always better.
One of the most underestimated factors in indoor growing is the humidity.
It is important for the further course of the entire harvest especially the first three weeks.
A cutting is a sprig of a plant with a few leaves, which is cut from a large plant, the
mother plant. This mother plant is selected on quality, gender, and strength and each
cutting from this plant has exactly the same characteristics, the genetic factors. Since
this cutting can vaporize water via the leaves, but cannot absorb water (there are no leaves)
it must be protected against dehydration. This is where humidity comes into play. By
increasing the humidity the water will vaporize more slowly and the plant will loose less
water than in dry air. You give the plant more time to grow roots this way. With the help
of the humidity you can actually regulate the rate of water evaporation in the plant. Even
if roots are already there it may be that a young or sick plant cannot keep pace with the
evaporation, for example if the amount of light or warmth is increased. You can recognise
it by more yellow leaves, dried out edges of leaves, a stagnating growth and a decreasing
Most of the time when you turn on the light the room will get too dry quickly.
Since cuttings will usually take root under strip lights they are not used to really
Initially hang the lamp(s) as high as possible, start with a few lamps and add more
lamps in the course of the first two weeks. Much light means much warmth. Much warmth
means much extraction to lead away the warmth and all humid air is transported outside.
Everyone will see the similarity between a blow-drier and the warmth of the lamps in
combination with the extraction. The more lamps, the warmer it gets, the stronger the
extraction so the lower the humidity, or the dryer the air. In order to maintain a
high level of humidity you must not use too much light initially so that the extraction
can be kept low. You can furthermore place water reservoirs, spray water, hang wet laundry
in your growing room or, even better, use a humidifier. Be careful that the humidity is
not more than 95% with reference to the electric equipment. When the plants get bigger
they will automatically use more water and give off more moisture to the air and eventually
the humidity will stay sufficiently high. When the humidity gets too high you can turn on
more lamps and/or increase ventilation.
The following values are advisable:
week 1 80 to 90%
week 2 70 to 80%
week 3 65 to 70%
week 4 through 8 60 to 65%
week 9 around the 55%
Nowadays there are various convenient climate controllers available that simplify the
controlling of your climate. Let someone inform you about the differences.
When you grow you will be visited by uninvited insects now and again. The cleaner you work,
the better, but it still does not guarantee anything. There will be no flowers the first
three weeks of the harvest. During this period you can use insecticide, which you wash
off before flower formation, without problems. I prefer insecticides that degrade themselves
within a few weeks and are not poisonous after that period. Let someone inform you about
this because there are also dangerous products on the market. Always ask about a product
that is suitable for vegetables, fruit and other consumer crops. A safety term is usually
also indicated. I furthermore advise to work with two different insecticides, one general
insecticide against louse, thrips and other insects and a special insecticide against red
spider mites (web). If you spray once every three days with one of the two insecticides
your crop will be clean before the real bloom. Primarily spray under the leaves.
Once you have an actual flower (and not the first hairs) you stop spraying and wash the
leaves a few times with a lot of clean water. You can also release natural enemies such
as predatory mites (orius) and soil-predatory mites (hypoaspis miles). The first lives
on all harmful insects on the leaves, and the other on all harmful insects in the soil
and for that reason they are particular suited to use preventively. Only tenacious red
spider mites might occur at the end of the harvest, against which you should use predatory
mites. It all seems a lot of work but it might save you a lot of problems, and fighting a
real plague is often more work and might cost more with reference to yield and quality.
Watering with coco is different than with soil. If you grow on soil you cannot give the
plant too much water because the plant will drown otherwise. Much water in the soil
displaces all oxygen, which is rare in the ground in any case. Pearlite is added to the
soil to reduce this problem. Coco on the other hand is so light that there will always be
sufficient oxygen left and the plant cannot drown. This means in general that you can give
the plant so much water that it drains from under the pot each time. You can let the pot
become dryer the first week only to stimulate root development. You can also water the plants
on coco the soil-growing way (without drainage), but coco is actually a hydrological medium
and drainage yields better and more constant results (750grams/600watt/9weeks/1.2m2 has been
You furthermore compare the EC-values (see following chapter). If they are constant, flush
out a little and drain 20% nutrient solution. If you measure a higher EC-value you can
drain more (30%) and flush out more often. When the EC gets lower, you can give more nutrients.
Unfortunately I haven’t seen a professional soil humidity meter yet. The hydrological growing
on coco always enables you to know if you have watered the plant sufficiently. From the 8th
day you must find on average 25% of the water given each day in the waste water reservoir
where your drain water flows back to. You can furthermore decide at all times to give more
water in order to regulate your pH- and EC- values.
E.C. means Electric Conductivity, and is measured in uS/cm.
The dissolved salts in water determine the conductivity of the water. If no salts or minerals
are dissolved in the water the conductivity is zero, just like rubber. The more salts, the
better the conductivity. Tap water normally contains so many dissolved salts that it conducts
electricity dangerously well. Since most salts are also nutrient the EC.-value is also a
standard for the nutritional value of the water or the soil.
The EC.-value of the tap water in the Netherlands lies approximately between the 0.1 and
the 0.7 uS/cm. The EC in this area lies around 0.5. When we talk about an EC-value it is
always a combination of the EC-value of the water and of the nutrient. The tap water has
an EC-value of 0.5. In case of an EC of 1.7 this is 0.5 of the water and 1.2 enriched with
nutrient solution. In your case you must complement the EC of your tap water with 1.2 EC
When the plants are young you should work with an EC of 1.2, up to 1.7 in approximately
If everything goes as it should you determine by looking at the colour of the leaves if you
should give more or less nutrient. If the leaves are dark green this means that the plant
has more than enough nutrients for now. You can give fewer nutrients. If the leaves turn
more yellow, you can give the plant more nutrient. Since there are also other factors that
determine the colour of the leaves you should measure the soil or the drainage water.
Pay attention when measuring the pH and EC if you haven’t had constant drainage. The
values measured may be unreliable. You should flush a few days with extra drainage before
you start measuring (see Drainage).
A normal EC-value near the roots for an adult plant lies around 1.6 and 2.4 uS/cm.
Try to give a nutrient concentration as low as possible, but as much nutrient solution as
possible. Work with Citral and white weeds with EC-values between 1.6 and 1.8 if you
have 20 to 30 % drainage water left.
When you drain less, you must generally give more nutrients. With K2 or skunk kinds you
can often give more nutrients in any case.
With constant drainage you can use the drainage water to determine after the 3rd/4th week
how much nutrient you must give. We work with an EC between 1.6 and 1.8mS/cm.
Since the plant absorbs a part of the nutrients the drain water (waste water) contains
fewer nutrients than the nutrient solution. If you give 1.8, you can expect back between
1.1 and 1.6. If you have given, for example, 1.8 the previous weeks and measured 1.5 in
your drain water you can increase the nutrient solution 0.2 points when the EC-value of
the drain water drops to 1.3, for example. This is a sign that the plant develops well.
If the condition of the plant deteriorates due to, for example, high temperatures the
plant will also absorb fewer nutrients and you will measure a higher EC of the drain water.
This is a bad sign, which is often noticeable before other symptoms such as discoloured or
You must lower the EC of your nutrient solution, and also look for the cause (bad climate,
bad pH or bugs).
On average you try to get an EC-value of 1.7 near the roots. The EC-value near the roots
lies around the EC of your nutrient solution and the drain water. All in all you can use
the following formula to determine the EC of your new nutrient solution:
EC of the new nutrient solution = 2 x [1.7 – (½ EC drain water)]. Here the EC drain water
is the EC of the old drain water left behind after previous watering(s).
Always watch the plant closely and never react rigorously. You should adjust your flush
water somewhat and use it to flush longer instead of flushing shorter with more extreme values.
If you measure an EC-value of the drain water that is higher than you have indicated on
the nutrient vessels you had too little drain or haven’t measured and adjusted often enough.
You can flush your coco on this moment until the values are ok again (see flushing). If your
plant stops growing due to stress it hardly uses nutrients. If you continue giving
nutrients without measuring almost all the nutrients you give will remain in the coco
and you will have an EC-value near the roots that will quickly get too high if you don’t drain.
If the leaves are yellow, do not increase your EC-values rigorously. Give a bit more
nutrients, but also water more often or give more water and during a longer period.
If you measure regularly you will never find strongly deviating drain values, and you
will only have to adjust minimally. Try to give a nutrient concentration that is as low
as possible, but give as much nutrient solution as possible.
EC-meters cost approximately Euro 40,-.
P.H. (Potentia Hydrogenica) is acidity. In plant breeding the pH determines the nutrient
absorption capacity. A pH that is too low (acid) causes certain elements to be absorbed
too quickly, which may cause poisoning. If you have a pH that is too high (basic) certain
elements will not be absorbed or with difficulty. A shortage is usually not caused by using
too little nutrients, but because the nutrients cannot be absorbed. You can have good nutrient
absorption on coco with a pH between 5.2 and 6.2 with a pH of 5.7 as ideal value.
Plants adapt to circumstances. For that reason constant values are always better. So keep
the pH constant!
The acids we use are nitric acid and phosphoric acid. Nitric acid or pH-grow (pH-min-grow)
is used in the growing phase and in the first week of the bloom, phosphoric acid or pH-bloom
(pH-min-bloom) is used after that. If the pH of your water with nutrients is lower
than 5.7 you need pH-plus. This is not acid, but a base, usually caustic potash.
Coco has, just like soil, the capacity to steer the pH, correct it and stabilise it.
This is caused by minerals in the coco that correct the pH. This means you can have at
least one harvest without regulating the pH of your nutrient solution. When you regulate,
up to 5 harvests are possible.
EC and pH are closely linked. If you add more nutrient to a bucket of water the pH
usually drops and if you add acid to the water the EC rises (a little). If you
continuously give a bit too much nutrient or if the plants absorb less nutrient the
EC-value in the coco builds up. The pH will also become more acidic (=lower).
If you grow hydrological on coco it is quite easy to maintain the correct pH-value
by means of the following formula:
PH of the new nutrient solution = 2 x [5.8 – (½ pH drain water)]. Here the pH drain
water is the pH of the old drain water left behind after previous watering(s). Test
your soil every three weeks or let a growshop check it. You can buy a pH-meter from Euro 40.
Good drainage prevents build up of acids and salts.
Drainage is the amount of nutrient solution that leaks from under a pot or slab after
fertilizing. The purpose of drainage is that the EC-and pH-values can be controlled
better and unnecessary salts are drained.
If you give a plant nutrient you try to give it exactly enough. Since not all plants use
similar amounts of nutrient and plants also secrete salts, there may be pots in which
salts are building up. This surplus of nutrient makes the soil brackish and changes the pH.
By means of drainage you flush the soil every time you give nutrient, which prevents the
soil becoming brackish.
If you measure the drainage water or the coco you can see if the soil is polluted. If
the EC is higher than you have indicated you must flush. You can also bring your water
or soil sample to the growshop. We can teach you there how you can carry out a proper
soil analysis and how you can determine from the values measured how to proceed. If the
values deviate strongly you can also, for example, flush half a vessel of nutrient
solution through the pots and measure again. If you still don’t have proper values
you can flush again a few days later. You can also slightly increase the drainage.
Try not to let the values fluctuate too much on 1 day, but flush with intervals of
a few days until the values are correct again. Too many fluctuations in a short while
can cause stress. Only measure drain water if you have regularly drained the past few
days, otherwise you measure unreliable values.
Step by Step
-Heat up the room to about 24 °C.
-Regulate the humidity between 80 and 90%.
-Turn on as few lights as possible (for example 1). Hang the lamp(s) as high as possible.
-Minimise the extraction or turn it off (see chapter humidity).
-Fill the pots completely, lightly press the soil.
-Give half a litre of water per plant according to the “planting recipe”.
-Give all plants, within 10 minutes after placing, water because the dry coco otherwise
sucks the cutting plug dry.
-Spray water, so that the plants and the room are humid, but do not let the coco
become wetter with spray water because the pH of that water has not been regulated.
- The blooming phase starts between now and 7 days depending on the kinds.
-Keep the humidity over 80 % the first week.
-From the 2nd day preventively spray insecticide, every three days up to flower
formation and primarily under the leaves.
-When the plants have grown a few centimetres, you can select the plants on size.
Place the large plants on the outside and the small ones in the centre.
-The more often you do this the more equal the plants develop.
-After about a week (between 5 and 10 days) the plants need water.
-Use the “nutrient solution recipe 1”. Only water the plants that are dry and let
the others become dry first (see selecting and ordering plants).
-You can turn on about 2/3 of the lamps usually after a week.
This depends on:
- the regulation of the humidity and
- the development of the plants in the first week.
Often these factors are connected.
If the plants, for example, during planting or due to low humidity have sustained
a shock it may be that they cannot stand so much light yet. In that case wait with
increasing the amount of light, all the more since this also complicates a high humidity.
-Keep the humidity between 70 and 80%.
-Keep spraying against insects.
-Order and select, in this phase only water plants that are dry, but generally
use a more humid pot for plants that do well. Water the plants with nutrient
1.-Slowly turn on and increase the air extractor (15 minutes/hour).
-Turn on the last lamps.
-Increase the extraction.
-Keep the humidity between 65 and 70%.
-Gradually lower the lamps, 600wat min. 50cm and 400wat min. 40 cm.
-Give water according to nutrient solution-recipe
-Spray until the end of the week.
-Increase the extraction.
- Spray the plants at the end of the week for the last time.
This depends on the kind and how fast the bloom starts.
- At the end of week 3 the soil humidity may rise until drainage starts.
If the plants are relatively big you can drain sooner, and the other way round,
because if the root system has not been developed enough yet a drier pot is
better since the plant sends out the roots for water.
Build up the drainage in the coming 2 weeks to at least 20%.
Also mind the drainage water; you might for example discover harmful soil
insects you don’t see usually. Of course you can also measure the water.
The more the values (pH en EC) deviate from the nutrient solution, the more
you must drain or flush. In case of large differences visit the growshop.
-Order the natural enemies that you want to use preventively from the growshop.
Assassin bugs and soil predatory mites are effective against practically all plagues.
Only tenacious red spider mites may sometimes occur. In that case I use predatory
mites, especially against the red spider mite.