How to grow a cannabis indoor grow room?
Building a grow room does require some knowledge. We provide this knowledge here in this blog so that you can create your own indoor grow room for your beloved plant for as little money as possible.
Whether you grow your own food or your own cannabis, growing your own is always best.
In this blog we talk about how to grow the cannabis plant indoor for convenience, but this also applies to tomatoes or other plants.
1.Decorate a room
What cannabis plants need to grow well and bloom beautifully is space, light, air, warmth and nutrition. If one of these conditions is less well met, other circumstances will not compensate for that lack and growth and flowering will be less successful. The grower, who works indoors, must therefore ensure that everything is (optimally) available for his plants.
1.1 Space
You don't need much space for growing cannabis indoor. A separate room of at least 3 by 3 meters is sufficient to grow about 48 cuttings in pots. Rate eligible spaces based on the following:
- Most suitable are rooms that already have a favorable climate for plants to grow in: fairly constant temperature in summer and winter, not humid and especially no moldy walls. The more favorable the space, the less intervention is required in the existing climate and the smaller the chance of failure.
- The space must be clean, so can/may everything that is not needed for the plants be removed?
- There must be options in the room to supply and extract air in a way that is not disruptive to yourself or outsiders.
- Electricity must be available in the room. Because the growing space is humid, the connection points must be grounded. If there is no earth conductor, you will have to install one yourself. A tap in the room is useful so that you don't always have to carry heavy buckets of water, but not necessary.
- Can the space be sufficiently shielded from the environment so as not to provoke unwanted curiosity? Consider the strikingly colored light of an incandescent lamp, but also the on and off of odorous fumes and the (almost) permanently present sound of a fan. Once you have found a suitable space, provide reflective walls by painting them matt white with latex or covering them with white reflective foil. This increases the light output available to the plants.
Close any windows, grilles, etc. from the outside world, but do not do this in a conspicuous manner. A boarded up window is more likely to raise questions than a window with a curtain (behind which a partition closes the case). You can find good tips about ways to make rooms light-proof in books about photography and especially about setting up a dark room.
Furthermore, a hook is needed on the ceiling on which a grow lamp can be hung and which can be connected by means of a chain or pulley must be adjustable in height.
The cannabis plants will soon be placed under this lamp, preferably on a plant table. This is a simple wooden box, which you line on the inside with pond liner and is therefore waterproof.
The size of the table top depends on the number of plants and the size of the pots in which they will be grown. For 16 plants in pots of 25 x 25 cm you should count on an area of at least 1.20 x 1.00 meters.
A handy hobbyist can take a strong pallet and use that as a grow table.
The table top is approximately 10 cm above the (cold) floor. Air can then circulate underneath, which prevents the cold from the floor from rising to the plants.
Around the table or pallet, you make a wooden edge about 5cm high. At the fishing store or growshop you buy a small piece of pond liner.
The pond liner you place on the pallet and fold it up over the wooden edge, stapling the liner on top of the edge. Of course, don't staple anywhere else to prevent leakage. This is important for watering from the bottom.
If you need the indoor grow room also for other activities, you have to close the table and make it a box. The simplest and cheapest option is to hammer wooden slats up against the pallet or table and connect them to the top with slats. You can then hammer wooden plates onto the slats, but it is even cheaper to staple white foil to them.
You can also choose to buy a ready-made grow box or grow tent.
1.2 The lighting
Plants need light to exist. Photosynthesis takes place under the influence of light, which converts food and water into the necessary fuels and chlorophyll is also formed, which gives the plant its green color.
Not all light is suitable for the plant. Plants need light with a certain spectrum and intensity. The grow lights described in this guide meet the requirements in terms of spectrum. We determine the light intensity by choosing a 400 or 600 Watt lamp, depending on the size of our garden, and placing it closer or further away from the cannabis plants. A good and safe distance between lamp and plant is between 30 and 50 cm.
The day and night rhythm offers the plant an active and a rest phase every day. In the growth stage the day may last up to 18 hours, i.e. you leave the lamp on intermittently for 18 hours. Any longer makes no sense and is unnecessarily expensive. For the day and night rhythm, let the lamp turn on and off at the same time every day. In the flowering phase, only 12 hours of light are needed. You can herald the flowering period by setting the timer 6 hours later or earlier.
There are many so-called plant growth lamps on the market. Most consist of a lamp of a certain strength, a reflector that contributes to an even distribution of light and a built-in ballast that ignites the lamp.
The installation of a grow light
A grow lamp requires a lot of power and the switch-on voltage is certainly high. For safety reasons, connect the lamp properly. For a grow lamp, use electricity cable with a diameter of at least 1.5 mm2. (Ask for cable for a washing machine connection).
An electrical installation in a residential home often has 16 Amp fuses in the "fuse box". Such a 16 Amp fuse may be loaded with a maximum of 3520 Watts (220 Voltage).
Expect that, if the grow lamp and all equipment in the growth chamber are turned on, the electricity grid will be charged an additional 500 to 700 Watts when using a 400 or 600 Watt grow lamp respectively!
So check which lamps, appliances, heaters, etc. also receive power via the same fuse to which you want to connect the grow lamp. Add up all the wattages and stick to a 16 Amp fuse on the safe side of 2800 Watts.
A timer is very useful to switch the grow light on and off at the correct time. When choosing the timer, look at the maximum amperage that can be connected to it and also allow a wide margin here. the high switch-on voltage of the grow lamp.
For more information about lighting, read this blog.
A few more comments
Grow lights for plants provide bright, coloured light. The color and times at which the lamp is lit tend to attract attention in the area. To avoid unwanted curiosity, ensure a light-tight seal between the plant room and the outside world. No light should escape outside, but no light should come into your plant room either; that can disrupt the day and night rhythm of the plants!
To learn more about light and dark, read this blog.
1.3 The air
Plants need fresh air and especially the CO2 it contains to grow. In an enclosed space, the cannabis plants consume the available CO2, after which the growth of the plants slows down and eventually stops.
Air ventilation and circulation also helps to regulate the temperature in the room, remove excess moisture in the form of water vapor and last but not least, moving air helps to prevent diseases.
Under normal conditions, the air is rich enough for our plants. However, if you have closed the growing space very well from the outside world and the air extraction is greater than the supply, there may be a shortage of fresh air. Your plants will become lighter in color and growth will slow down.
The solution is to supply more air by installing an (extra) air grille in the door if necessary. Remember that an air opening must also be light-tight so as not to disrupt the day and night rhythm of the cannabis plants!
Air ventilation
The principle is simple: When you extract air from a room, a negative pressure is created (a kind of vacuum). New air then automatically flows into that space through the existing cracks.
As a rule of thumb, it should be possible to extract all the air in the room in about 10 minutes. To determine the required power of a fan, first calculate the volume of the plant room: length x width x height. This gives the volume in cubic meters. Multiply this number of m3 by 6, then you will know the power per hour required to refresh the room in ten minutes.
Furthermore, fresh air must be able to flow into the room when it is sucked out. Therefore, ensure sufficient air supply; If necessary, you can make a (light-tight!) opening somewhere for extra air.
Find out where you are going with the extracted air. An unused chimney with a drainage hole (to be made) just below the ceiling is ideal. A passage through a window quickly causes problems with the light sealing of the room and, just like a passage through the wall to the outside, there is a risk that the special plant scent in the air will make neighbors or passers-by undesirably curious.
Remember that the exhaust fan will be used intensively and for a long time, so look for a solid device. In addition, look for a low-noise device so that you or your neighbors do not wake up at night when the fan starts running.
When purchasing an exhaust fan, pay attention to the following points:
- Sufficient extraction power
- Suitability for proper attachment
- It must be quiet
- Possibly be able to suck slowly and quickly
Frequently used fans are the 'snail shell' type or the 'box' type that is used for mechanical air exchange.
Switching the fan
The fan must ensure that the air is regularly refreshed, especially during the day (when the lamp is on): 5 to 10 minutes every half hour.
This allows the fan to be connected to a timer, which switches on/off at set times.
To prevent the humidity or temperature from rising too high during the night, you can ventilate once every three hours when the lights are off.
Constant ventilation with a switch that can make the fan run harder or softer based on temperature is the most ideal.
Such systems are for sale in every grow shop.
Air circulation
Make sure that the air in the entire room, including the dead corners, is supplied with fresh air. A moving air flow prevents local CO2 shortages and keeps the entire room at a constant temperature.
In addition, many parasitic and disease-causing creatures thrive poorly in a 'dark' environment. Purchase a room fan that can at least swivel. Place it in a strategic location so that every spot in the room is reached by the air flow.
Adjust the power of the fan (if necessary using a dimmer switch) so that a gentle breeze flows through the entire room and the leaves of the plants move slightly.
A gentle breeze through the plants refreshes the air and the movement also makes the stems sturdier!
Perhaps it is unnecessary to say that a gale-force wind is not better, but actually worse for the plants.
Odors
Many people find to grow cannabis indoor have a strange smell.
They are right: the soil, the manure and certainly the plants give a very special smell, which can be smelled throughout the house without measures.
How to grow cannabis indoor without smell? You prevent people from turning their noses up at your hobby by placing a so-called ionizer in the growing room. This device electronically generates negative ions, which are blown through the room with or without a fan and neutralize the (odorous) dust, mold, etc.
A good ionizer uses very little power and can prevent many problems.
If you are afraid that your hobby can also be smelled outside, consider including a carbon filter in your ventilation system. Such a filter box is easy to place between the extractor and the air exhaust duct.
1.4 The temperature
The internal functioning of plants is closely related to the temperature in the environment. Cannabis plants thrive best at a daytime temperature between 23 and 26 Celsius. At night the temperature may be a few degrees lower.
Check how warm or cold the room is in which you want to grow the plants. Keep in mind that the grow light you will be using is a large heat source. Often the lamp alone is sufficient to keep a small room at the right temperature during the day!
When choosing a room, remember that heating is easier and cheaper to produce than cooling. An attic quickly overheats in the summer and requires particularly good insulation. A basement space, on the other hand, often remains too cool and requires additional heating.
A cold room needs to be (additionally) heated. The following options exist for this, each with their own advantages.
- Central heating: This may be present in the room. The warm central heating air is very dry and therefore very suitable in damp rooms. The heat can also be easily dosed using a thermostatic valve on the radiator.
- Electric heater: If there is no heating in the room, an electric heater is easy to connect. However, electric heaters are power guzzlers and be careful not to overload the installation in the room where you already use a lot of power for the lamp! If you opt for electric heating, preferably buy an oil-filled radiator with thermostat because these are safer in damp areas than radiant heaters.
- Gas or oil heaters: Choose a version that does not need to be connected to a chimney. Gas and oil heaters have the disadvantage that they always have to be turned on and off and often do not have a thermostat to regulate the temperature. In addition, they increase the humidity of the air. A major advantage is that combustion produces extra CO2, which is beneficial for growth. Watch out for fire hazards because you won't be in the room all day to pay attention.
Hang a so-called minimum/maximum thermometer in various places in the growing room. This allows you to always check whether the temperature remains within safe limits during the day and at night.
A room that is too warm must be cooled down. This is done with the same exhaust fan, which also provides air exchange. We have air that is too warm extracted and replaced with cooler air from elsewhere. To regulate the temperature, a room thermostat for the central heating system can serve as a temperature switch. The thermostat must then be able to switch in reverse, i.e. it must switch on if the temperature becomes too high.
Ground temperature
The temperature of the soil in the pots produces the best chemical reactions when it is between 19 and 24 C. By adjusting the temperature of the irrigation water, a somewhat high or low temperature can be compensated.
The perlite or coco contained in the soil mixture helps maintain the temperature of the soil. In any case, make sure that the temperature of the soil never exceeds 25 C. The soil will then dry out the roots and without functioning roots (a little later) there will be no plant!!
To get the best out of the cannabis plant with temperature control, read this blog.
1.5 Humidity
The temperature also has a major influence on the humidity of the air. Warm air can contain much more moisture than cold air. A relative humidity between 40 and 60% is ideal. This can be measured using a (hair) hygrometer. An air humidity of 70% or more is bad for growth and flowering and increases the risk of diseases.
Controlling humidity is also done with the extractor fan. We have excessively moist air extracted and replaced with drier air. A humidistat does the same as a central heating room thermostat, but for moisture. We also connect this to the exhaust fan. Please note that these devices often operate on low current and you must use a relay to switch a fan to 220 volts!
Water is the means of transport for nutrition inside and outside the plant. The humidity in the room therefore has a major influence on the metabolism in the cannabis plant. Humidity is a relative concept: warm air can contain more moisture than cold air.
The relative humidity is indicated on a scale ranging from 0 (extremely dry) to 100 (soaking wet) and is measured with a (hair) hygrometer.
At high humidity, water evaporates less quickly. The pores of the plant close because the plant can exhale less moisture and growth is therefore slowed down. An air humidity of 80% or more also provides ideal conditions for the mold that lurks!
At low humidity, water evaporates faster. The plant opens its pores and can lose its moisture well and grows prosperously as long as it has enough water. Of course, the humidity should not be too low to prevent dehydration. A relative humidity between 40 and 60% is ideal for growing cannabis.
Too low humidity
If the humidity is less than 40%, you can add moisture by lowering the temperature in the room or hanging out wet cloths. If low humidity is a chronic problem, consider purchasing a humidifier (with built-in hygrostat).
Too high humidity
If the humidity is 70% or more, ensure a higher temperature or have the moist air in the room extracted and replaced with drier air. If the room in which you want to grow, for example a basement, is so humid that you cannot get or keep the humidity within the standards, then you can buy a very expensive dehumidifier or (better) look for a drier room.
2.1 Soil
Cannabis can be grown in different ways: in normal soil, hydroponically and in soilless soils. To begin with, because of our familiarity with plants in the ground, it is easiest to work with regular soil. The quality of the soil is determined by its structure, acidity and nutrient content.
All soil mixtures are composed of the following components:
Potting soil:
is available at all garden centers and contains sufficient nutrition for the first time. Supplementary feeding must then be given. Choose potting soil that is packaged in plastic, as these are less likely to contain pathogens. Check whether the packaging states the pH value of the soil: it is preferably between 5.5 and 6.5.
Worm manure:
this is compost that has been digested by worms, making the nutrients immediately available to the plant. If there is a choice, prefer fine rather than coarse worm manure. Never use more than 30% worm fertilizer in a mixture, otherwise root growth will be seriously compromised.
Pre-mix:
this is a special combination of concentrated fertilizers that our plants can use for their rapid growth and flowering. Pre-mix contains minerals, blood and bone meal and guano.
Perlite:
these are white granules that help regulate the water balance in the soil, retain nutrients and make the soil airier. When purchasing, make sure that you use agricultural perlite with chalk and not with construction perlite that contains cement.
Lime:
is added to the soil to stabilize the acidity and thus the pH and also contains the necessary calcium and magnesium. Lime is difficult to absorb, so choose a powdery lime, for example MAERL lime, which is available in 5 kilo bags. The amount to use depends on the pH value of the mixture. Usually, 5 to 10 grams per liter are used.
Coco:
The coconut fiber comes from coconuts and is a fiber that provides a lot of air in the soil and regulates the water balance well. The advantage of coco compared to perlite is that the soil mixture can be thrown into the garden without immediately having white perlite granules in the soil.If you reuse the mixture and supplement the cannabis plant with liquid fertilizers, perlite will eventually form algae, which affects the pH of the soil. With coco you have no problems with that.
If you use a high-quality liquid fertilizer, you can even last a few years with the same soil mix if you use coco instead of perlite.
There is a lot of experimentation with soil. To a certain extent this is necessary to find out which soil mixture leads to good results in a particular situation. People often talk highly about the super results achieved by adding extra or strong fertilizers or using special additives.
This is of no use to the novice grower. For normal growth and flowering of cannabis, the soil composition below can be maintained. All parts are normally available in garden centers and of course grow shops.
A good soil mixture is:
| Potting soil | 70% |
| Pre-mix | 1% |
| Wormcast | 14% |
| Perlite or Coco | 15% |
| Maerl Lime | 5 to 10g/litre |
As stated earlier, the quality of the soil mixture is determined by the acid/base ratio and the nutritional value. The acid/base degree is indicated by the pH value of the soil. A pH value between 5.5 and 6.5 is ideal, but a value between 5.4 and 6.2 is best.
To learn more about pH, read this blog here.
The nutritional value of soil is generally indicated by the NPK value of the soil. This represents the ratio between the fertilizers: N (nitrogen), P (phosphorus) and K (potassium).
The nutritional value of the soil can be measured using an Ec meter. This Ec value must be around 2.0 if you do not give fertilizer. You can determine the quality of your soil mixture yourself or, if you do not have your own meters, it can be examined by a garden center. It is important that you check that the soil mixture with which you start the cultivation is fine.
2.2 Pots
The cannabis plants are meant to grow quickly. The plant grows (invisibly) just as fast underground as above the ground. So give the roots space in a pot with sufficient capacity. It is useful to give each plant its own pot. This makes the cannabis plant easy to handle individually.
A plastic pot of 15x15x20 cm has a capacity of 4 liters and is ideal for containing sufficient soil and therefore nutrition and offers sufficient space for the roots of plants that will grow to approximately 50 cm in height. In addition, this size pot has the advantage that the generous content retains sufficient moisture so that the risk of dehydration is reduced.
Choose a square pot: it has a larger capacity than a round one and can easily be placed in rows.
2.3 Tools
With all tools, it is preferable to only use them for your plants and keep them in the growing room. This prevents you from having to search or bringing dirt and animals from elsewhere into the room.
The most important tool in the cannabis garden is the moisture meter, which can be purchased at any garden center for little money. With this meter you measure the moisture level of the soil. You then know exactly when the plant needs to be watered again. I prefer measuring to digging into the pot with your fingers to feel how wet the soil still is. With experience you can later feel by the weight of the pot whether water needs to be added. For a good metabolism of the plant, a soil temperature between 18 and 23 Celsius is required. You regularly check this temperature in the soil with a special soil thermometer.
An electronic thermometer to measure indoor and outdoor temperatures is very useful. The cord carrying the sensor for the outside temperature is placed in such a way that it measures the temperature at the top of the plants under the lamp. This temperature should not exceed 30 Celsius to prevent the leaves from drying out. With such a meter you can read exactly when the plants are in danger.
Provide a plant sprinkler with a capacity of five or ten liters, which can be pressurized with a pump system and thus provides a fine mist.
This sprinkler is used to occasionally 'rain' the plants clean and to provide foliar nutrition if necessary. The sprayer can also be used to spray a pesticide if necessary. If you do this with the same nozzle, you will of course clean it very well after use.
If you want to keep a close eye on the ripening stage of your plants to determine the right time to harvest, you can purchase a magnifying glass. There are very handy magnifiers available for little money with a magnification factor of 30 and built-in lighting.
The mini garden also requires a few small hand tools. An old fork can work very well as a rake to keep the soil around the plants loose. If necessary, bad leaves can be cut from the cannabis plant with sharp scissors. Tearing off leaves can cause unnecessary damage to the plant. If you want to keep track of how much the plants are growing, keep a measuring stick of about 60 cm long available in the room
The cultivation
4.1 Growth stages
Our cannabis plants are annual plants that can grow to a height of about two meters in the wild. Indoors, plants of a more modest size are generally grown. In their lives, cannabis go through three clearly distinguishable stages:
Stage 1: Cuttings
Once the seeds have germinated and rooted, we have seedlings. The male seed-forming plants can be separated from the female ones, which can then flower nicely. As a novice grower, you prefer to start with cuttings because self-sowing, cuttings or cloning is an art in itself.
Because we want flowers, we can only use female plants. A good breeder ensures that you only get females.
If you are going to buy cuttings or clones, assess the plants on the following points:
Good
- Each leaf has 5 or more fingers.
- The stem is transparent and not woody.
- The roots are short, thick and have fine root hairs.
- The entire container smells good and is fresh green.
Bad
- 3 or fewer fingers.
- Red, woody stem.
- Thin, winding roots without fine root hairs.
- Brown tips at root ends.
Stage 2: Growth period
The cuttings are planted in the 25x25 cm pots and enter the vegetative stage.
Growth is central during this period. A healthy plant grows about one cm per day, forming a beautiful and regularly shaped dark green foliage.
An extensive root system develops underground. This requires a 'summer' period in which the sun shines continuously for at least 18 hours and sufficient food is available.
When the cannabis plants have reached an average length of 15cm after one/two weeks, they have enough potential to start flowering successfully.
Stage 3: Flowering period
When the days become shorter, which the grower simulates by leaving the lamp on continuously for only 12 hours, the plant starts to flower.
Growth slows down but continues and a 15 cm plant will eventually reach a length of about 50 cm.
During this period, female plants produce flowers and attractants and the plant hopes for fertilization. During this period the plant receives adapted nutrition that promotes flower formation.
The discolouration of the pistils in the flower clusters announces the end of the cannabis plant. In the last week you still water the plants, but no more fertilizer. In order to be fertilized, the cannabis will produce an extra amount of attractant. Anyone who wants to keep some of the beauty must start harvesting now.
4.2 Growth and flowering calendar
Many growers want to make optimal use of their (expensive) facilities and try to grow cannabis plants several times a year. It is not possible to indicate exactly how much time a cutting needs to mature, flower and ultimately mature. Nature is too capricious for that.
The following times therefore only provide a good indication on which the grower can make a global plan for his garden.
The hardworking grower, who does not like being a slave to his garden every day, can grow cannabis plants up to 4 times a year. If you are not such a workaholic and want to continue enjoying your cannabis hobby, then 3 harvests a year is fun.
5 Watering
It is preferable to use the moisture meter to check daily how the moisture content of the soil is decreasing. Be careful not to damage too many or too many roots. Plants with few roots absorb less water than healthy plants. So be careful with watering in the beginning.
If the meter indicates that the soil is becoming (too) dry, then it is time to start watering.
It is best to water in the morning because excess water then has time to evaporate throughout the day. This reduces the chance of mold.
Use tap water with a temperature between 19 and 24 C so that you do not unnecessarily shock or burn the roots.
Be sure to check the pH value of the water.
This may be on the high side in different municipalities. The pH of the water should be between 5.4 and 6.2; ideal is 6.0. If necessary, bring the water to the correct value by stirring in pH increasing or decreasing agents.
When the cannabis plants are small, water from the top of the pot. When the plants are larger and the roots have grown far enough into the pot, water from the bottom.
You can simply water from below by filling the pond liner with water about 1 to 2 fingers high. The water is automatically sucked into the pot.
When the water on the pond liner has run out, do not add new water yet because the pots of soil are still quite wet.
Feel the weight of a pot when it needs to be watered again. This is usually 2 days after the water has disappeared from the pond liner.
If the soil is very dry, add a few drops of dishwashing liquid to the irrigation water. The soil will absorb water better.
Once a month, spray the plants with water until the water drips from the leaves. This way you remove dust and dirt that can clog the pores. Spray water is 'prepared' in the same way as irrigation water. Do not spray the plants when they are in full bloom. The water that accumulates in the flowers is difficult to drain and the flower can rot.
5.1 Fertilizing
Manure
The cannabis plant must receive sufficient nutrition. What the plant especially needs is:
N (nitrogen) for chlorophyll and leaf growth.
P (phosphorus) for energy production and root growth.
K (potash) for transport and flower and fruit growth.
During growth you can use a little more phosphorus, while during flowering there is a greater need for potash.
To provide this, various types of fertilizer are available for sale for growth and flowering. In addition to these primary nutrients, the plant also needs calcium, magnesium and a lot of trace elements. These are present in sufficient quantities in good types of fertilizer.
Types of fertilizer
Organic, Biomineral and chemical fertilizers are available. It just depends on what you like.
Organic fertilizers such as fish emulsion, bat guano, etc. can vary in composition due to their organic nature and often have a limited shelf life.
Spoiled organics can cause catastrophe in your garden, so always ensure freshness before use. On the other hand, organic fertilizers are very easily degradable, so that no residue remains in a harvested plant that could affect further use.
Biomineral fertilizers are derived direct from mineral sources and organic sources, where the organic elements have undergone a purification process. The shelf life of biomineral fertilizers lies between organic and chemical fertilizers. Biomineral fertilizers are more sensitive to cold.
Chemical fertilizers have a good NPK composition, are cheap and a long shelf life, but you don't know what the substance will do to a human body and nature. Also, chemicals cannot be used for all the functions in a plant that a nutrient should do.
If you are looking for fertilizer, always ask in the store for fertilizer that is specifically suitable for growing cannabis.
General fertilizer tips
- If the leaves lose their shine, become pale and yellow or growth slows down, it is time to fertilize.
- Fertilizing is always combined with watering. So take this into account with your 'watering plan' or opt for foliar feeding.
- Plants mostly absorb nutrition during the day. Therefore, provide fertilizer early in the day, so that the plant has the opportunity to absorb nutrients during the clear day.
- When preparing the fertilizer, stick to the prescribed quantities. Also check after preparation whether your water/fertilizer mixture still has a good pH value. Be careful with the amounts of fertilizer you use. Don't try to force growth/flowering. Remember that once a plant has been overfertilized it will not easily get rid of its overdose and that an under fertilized plant will simply receive some more fertilizer.
5.2 Over-fertilization and malnutrition
Over fertilization
The cannabis plant cannot process too much fertilizer and accumulates in the soil, leading to burning. The plant initially seemed to be growing well and was intensely green, but suddenly the leaf tips turned yellow and brown and died or curled up.
You can try remove excess fertilizer from the soil by 'washing out' the soil. Place the pot with the plant in a sink or container and pour the soil with water until it runs out of the bottom of the pot. Do this a few times until you feel that enough water has gone through the pot. Put the cannabis plant back and give it a few days of rest and pay attention to whether any new leaves start to act 'strange'. If necessary, repeat this treatment.
If this dos not work, send an email to helpdesk@metrop.nl to solve the problem.
Malnutrition
Malnutrition does not mean that you have not given the plant (enough) fertilizer. This is often (partly) due to the fact that the plant cannot absorb the nutrition properly, for example due to an incorrect pH value of the soil or a to gold temperature. So you check this first.
The most common food shortages are:
- Leaves that turn yellow-green in color and later die indicate a nutrient deficiency. If the discoloration started at the bottom of the plant, the plant is deficient in nitrogen. The remedy is to fertilize with a fertilizer that mainly contains N with Ca (CalciumNitrate) or regular 'NPK fertilizer'.
- If the cannabis plant suddenly starts to produce smaller leaves and grow less, this indicates a phosphorus deficiency. Then give a fertilizer that contains a lot of P (phosphorus) or regular 'NPK fertilizer'. A phosphorus deficiency is always recognize by the forming of Nitrit in the stems. (red stems)
- Leaves that turn yellow while the veins remain green(er) and later curl and then die are an indication of a magnesium deficiency. You can supplement this shortage by adding Epsom salts to the irrigation water (20 grams per 10 liters). If your fertilizer contain MgO, than look why the MgO is not absorbed by the roots.
LED lights that do not give the full spectrum will for example give a MgO deficiency.
5.3 Ec-Meter
Plants that experience rapid growth/flowering must have sufficient nutrients. To measure the nutritional value (actually the nutritional salts) you use an Ec meter.
In the same hobby range as the pH meter, a good and reasonably accurate EC meter is also available for sale at each growshop. This does have a built-in temperature correction, which allows you to measure liquids at any temperature. When purchasing, immediately purchase a bottle of calibration fluid (with an Ec value of 14). For more information about EC click here.
Malnutrition
If the Ec value has fallen below 0.6mS, which you can also see from the leaves turning a yellow-green color, you will have to feed the plants additionally.
