Basic Requirements for the Cannabis Plant Growth.

2009.05.05

All plants need nutrients, carbon dioxide, water and light to grow. (Plants also need small amounts of micronutrients like Magnesium and Zinc.) The basic nutrients are Nitrogen (N) Phosphorus (P) and Potassium (K). All fertilizer bottles have an “NPK” rating that represents relative amounts of each. Nitrogen promotes leaf growth. Fertilizers high in “N” are suitable for the initial growing, or vegetative, stage. Flowering or bloom fertilizer formulations have larger percentages of Phosphorus and Potassium as these two nutrients are needed at that stage of growth. There are many fertilizers on the market. Most growers should choose something organic like fish emulsion, bat guano or kelp.

People suffering from immune suppression should consider using a commercial fertilizer like “Peters 20-20-20”. Use commercial fertilizers with care. They are very concentrated and “overdosing” can kill the plant. Organic fertilizers are less concentrated and “easily digestible” by plants. For the planting medium use a general purpose sterilized planting mix.

Carbon dioxide (CO₂), present in small quantities in the air, is the colorless gas which mammals exhale as a by-product of respiration. Carbon dioxide is a fundamental requirement for plant growth driven by the energy of sunlight (or artificial light) through the process of photosynthesis. (This process produces the oxygen (O₂) which animals breathe, completing this symbiotic relationship.) Increased CO₂ can spur accelerated plant growth. Some growers add supplemental CO₂ to their plants but this is not recommended for beginners because of the complexity and expense. Most plants will grow fine with available air. (Use fans to help bring in fresh air.)

Water is the third essential. Keep plants watered but not soaked. A moisture meter is a simple and inexpensive device to measure soil moisture. Most plants can be planted in 1 or 2 gallon containers and irrigated every 2nd or 3rd day. (There should be holes in the bottom of all containers to allow for drainage.) Large sativas should be planted in larger containers, like 5-gallon buckets. They should also be flushed with large amounts of water to leach out salts and sprayed with lots of water to wash bugs and debris off the leaves about every 2 weeks. The hotter the space the more water the plant will need. Fans should be used to vent excess heat which can be monitored with an inexpensive thermometer placed on the wall. Venting also helps control excess humidity which can lead to mold.

Indoors or out, Cannabis plants require high levels of light for healthy growth. Outdoor growers rely on the sun, which is both inexpensive and powerful. (They also avoid the cost of ventilation.) Indoors, the light timing cycle should be set to 18 hours on and 6 hours off for vegetative growth, the first phase of the plant’s growth. An Intermatic brand timer makes this safe and easy. Cannabis plants typically grow indoors to the height of 2-4 feet before flowering. As there is much variation in size due to the many varieties. Each variety has different genetic characteristics that result in unique features. Sativas are generally not adaptable for indoor growing. Many varieties combine qualities from different sources. No single plant will be as useful as those from these carefully bred combinations. The inexperienced grower will need to experiment by procuring seeds or clones and growing them out. New growers should be patient and observe the plant’s development to learn what a healthy plant looks like. Attention to the plant, aided by study of cultivation references, will help in understanding how to care for the plant through all the stages of its life.

Since the number of flowering plants allowed under the OMMA is three, growers may consider growing the plants larger if the space is available.

Genetics and environment determine the flowering of Cannabis. Generally Cannabis will attain floral maturity after about 50-70 days.

Most hybrid varieties have specific flowering profiles such as number of days to floral maturity and physical appearance. Fertilize the plants on day 1 and day 25 with flowering fertilizer in concentrations recommended by the manufacturer for tomatoes.