Cannabis is a robust plant and does not need excessive care. However, there are some very important aspects to keep under control to ensure that the plant grows strong and vigorous and gives abundant harvests. Cannabis under stress sends clear signals ; knowing how to recognize them and acting promptly is the only way to save the crop and enjoy the fruits (and flowers!) of one's work.
Cannabis needs water and nutrients , a correct alternation between hours of light and hours of darkness and to grow in a well-drained substrate . When one of these factors is altered, the plant goes into stress and manifests it with more or less evident signals.
Below is a list of the most common sources of stress and the main remedies.
Water is essential for all plants, and of course it is for cannabis too. It is a necessary element for the correct carrying out of photosynthesis: it penetrates the plant from the roots and, through the stem, reaches the leaves. It evaporates from the leaves and is exchanged with carbon dioxide, thus completing the photosynthesis cycle.
Water stress occurs when the cannabis plant receives too much, or too little, water. Plants in lack of water can be recognized by their limp leaves and dry soil; the excess, on the contrary, stiffens the leaves. It is important to water cannabis plants correctly , and provide them with water from below: in this way the roots will develop at their best and the plant will acquire nutrients in the most correct and natural way possible, that is, from top to bottom.
Light is the other element necessary for the process of photosynthesis: plants use the energy obtained from light to produce chlorophyll , the pigment that makes leaves green and converts light into carbohydrates , which the plant uses as an energy source. Darkness is necessary for the plant's respiration, and for the release of carbon dioxide.
Plants need a regular and balanced photoperiod , as similar as possible to the natural alternation of day and night. The light that must vary slightly, depending on the growth phase: it is 18 hours of light during the vegetative phase, and 12 hours during flowering. In addition to light cycles, it is essential to plan proper indoor lighting to provide plants with what they need. A lamp that is too close or too far away may not provide enough light to the plants and too close distances could also cause thermal stress.
Roots are the foundation of the plant and are also its main tool for absorbing minerals and nutrients.
Even though they seem like a hardy part, the roots need some environmental requirements to thrive. They need access to air, water and the correct amount of nutrients : to do this they need to develop in well-drained soil, in which they can breathe properly. By keeping the soil temperature stable, you will ensure that the roots can carry out their task of absorbing water correctly.
Cannabis needs to grow in soil with a pH between 6 and 6.5 . pH levels indicate the acidity and alkalinity of the soil . The higher the numbers, the more alkaline the soil will be, and vice versa. The pH of the water used for irrigation must also be within the same range. In hydroponic crops the optimal pH range is lower, between 5.5 and 6.5.
An error in managing the soil pH can prevent the plant from correctly absorbing nutrients , sending the cannabis into nutritional stress, characterized by yellowing of the leaves.
The main nutrients for the cannabis plant are: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, sulfur, calcium and magnesium . Minor nutrients are molybdenum, copper, boron, manganese, iron, choline and zinc.
Cannabis needs to take in all these nutrients in a balanced mix to survive, and any imbalance can create a stressful situation for the plant. Excess or insufficient nutrients can create imbalances and deficiencies , which prevent the plants from carrying out their vital functions correctly. This type of stress is recognized by slowed growth, variation in the color of the leaves or their falling.
Tissue damage can occur after the plant is hit too hard, falls to the ground, is cut in an inappropriate place, or is attacked by animals or pests . Plants are quite resistant against these eventualities, and will be able to handle this type of stress, if the parasites are eliminated and the blow was not too violent.
- Environmental stress
The environment in which the plant grows will determine its yield, health and size.
For example , the cold can stress plants. It is important to ensure that you do not expose your plants to very low temperatures at night , whether you are growing in a greenhouse or outdoors. Likewise, if temperatures become too high , cannabis will be subjected to thermal stress which could permanently damage the leaves, thus affecting overall growth performance. In the greenhouse it is necessary to use thermometers and dehumidifiers , while outdoors you can use sheets to cover the plants and protect them from cold and frost.
As a general rule, the optimal temperature range for cannabis is between 20 and 28°C ; it may vary depending on genetics, but it is still a range to aim for.