I am new to growing and have heard that certain fertilizers may be bad for cannabis. Can you tell me why salt-heavy synthetics like Miracle Gro, or other artificial nutrients, are not good for my plants?
– Bobby S. via NicosNuggets@hightimes.com
Greetings, Bobby. Thanks for writing in with a great question!
Feeding your cannabis plants is one of the more difficult aspects for new growers to master. To start, it is important to understand that a plant’s food is derived from photosynthesis, which creates sugars (glucose) that the plant uses for energy. The nutrients that we give to a plant are broken down into mineral elements that are used in the photosynthetic process to create this food.
The easier it is for these nutrients to breakdown and get absorbed by the plant’s root system, the better nutritional value the fertilizer has for your garden. Organic (and especially veganic) nutrient lines are now available almost everywhere, and these products will be easier than synthetic fertilizers for plants to ingest. Artificial or synthetic nutrients are salt-based. Not only are these salts harder to dissolve in water, and therefore harder for roots to uptake, but these salts can also build up in the grow medium causing severe problems for plants.
Nutrient lock-up occurs when salts from fertilizers build up in your grow medium, preventing the root system from being able to absorb the minerals needed to produce sugars during photosynthesis, essentially starving your plants. As a general rule, it is always best to start with a mild nutrient solution, as you can slowly increase the dosage as you get accustomed to your plants’ needs. Doing the opposite—giving plants too much—can result in nutrient burn of the roots or nutrient lock-up from the build up of excess salts. Once lock-up occurs, you will see visible signs of nutrient deficiencies in the discoloration of the leaves. However, by this point, much damage as been done to the plant. The best chance for saving the plant is to begin a 7 to 10 day flushing regiment using only fresh, pure water with zero fertilizers.
Whenever possible, always first dissolve solid nutrients into a liquid nutrient solution before applying to your garden. The dosing instructions from the manufacturer are good guidelines to follow, though it is good advice for new growers to start by using half the recommended dosages and slowly working up to full regiments, monitoring the progress of the plants’ development along the way. The N-P-K (nitrogen-phosphorous-potassium) ratio should be higher in nitrogen (N) during the vegetative phase and then slowly wind down while increasing the phosphorous and potassium (P, K) during flowering. By the end of the flower cycle, the leaves will naturally begin to turn yellow from the lack of N. This is normal and correct. The last 10 days to two weeks of the flower cycle is commonly reserved for fresh water feeding only, so as to leach out any excess nutrient build-up from both the grow medium and the plants themselves. This helps prepare your buds for harvest and for the drying and curing stage. The cleaner the buds, the cleaner your smoke will burn—and taste. Using organic nutrient lines will go a long way to help achieve the quality flowers we all desire most.
Thanks for reading everyone and remember: Grow… And help the world grow, too!
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Don’t miss the previous Nico’s Nuggets: Understanding Grow Mediums & Additives