Soil growers – unless you’re growing with composted super soil, you will need to get cannabis nutrients made for soil to make sure your plants produce at their best. Even if you started with an amended soil like FFOF, you will still need to start adding nutrients once you reach the flowering/budding stage as cannabis plants are heavy feeders and your plants will have already used up most of the nutrients in the soil by the time budding begins.
Soilless & Hydroponic growers – If you are growing in any medium besides soil, like a soilless mix or directly in water, you will want to get cannabis nutrients specifically made for hydroponics. Some nutrients are even more specific; for example, Canna Coco is formulated to work best for growing weed in Coco Coir. For hydroponic grows, I highly recommend the General Hydroponics Nutrient Trio – here’s the cannabis-friendly GH trio nutrient schedule I use with my cannabis plants.
One nutrient system to rule them all…
Looking for a suggestion? One of the simplest (yet inexpensive) nutrient systems that works extremely well for beginning cannabis growers is Dyna-Gro (Grow, Bloom)
Dyna-Gro can be used at half-strength in soil, water, coco coir, or any growing medium and works amazingly well for growing cannabis. It does not build up salt in your growing medium like many other inexpensive fertilizers, and it will never clog your hydroponic system.
Just use the “Grow” bottle during the Vegetative stage and the “Bloom” bottle during the Flowering stage. You can actually follow the instructions on the bottle. It’s super simple.
Like all nutrient systems, avoid starting at full strength or it can burn your plants! Learn more about nutrient burn. Only raise the dosage if you notice that your lower leaves are turning yellow and falling off (except in the last 2-4 weeks before harvest, when yellowing lower leaves is a natural part of the maturation process)
Learn more about cannabis-friendly nutrient systems
Before I address pH, let’s talk about the “hardness” of your water…
The “hardness” of water describes how much extra “stuff” (like minerals and/or impurities) is contained in your regular tap water. You can contact your local water supplier for more information (ask for a “municipal water report”), or you can test the PPM of your water at home. Generally, as long as your water has less than 200-300 PPM (parts per millions) of extra stuff, it should be okay to use it for growing. If you are worried about the quality of your tap water, you can choose to use purified or Reverse Osmosis (RO) water, but you may then need to add extra Cal-Mag and possibly a few other supplements to help make up for the random minerals and nutrients that are normally found in tap water. I’ve personally always grown with straight tap water (in a big city in California with a natural PPM around 370, which is pretty high), and I’ve never had a problem. However, some places have very hard water, or tap water with unacceptable impurities, and growers in these areas will likely need to use purified water to get the best results.