Using tap water to mix your cannabis fertilizer with is perfectly suitable for your plants as long as you follow a couple of important steps. Since the water in many municipal water systems is treated with chlorine, and plants don’t like chlorine, it’s a good idea to get rid of it. You can do that simply by letting the water sit in an open container overnight before using it, which gives the chlorine enough time to evaporate.
The other guideline to follow is to only water your plants with water that is close to your grow closet’s temperature. The hotter or colder the water you use, the more shock you administer to your plants, slowing their growth and development.
The ph balance of your nutrient solution is also extremely important. Cannabis plants prefer their liquid foods to be on the slightly acidic side of the ph scale. A ph level of between 6 – 7 (7 being ph neutral) for your nutrient mix is perfect. As part of your grow closet supplies, you should buy a ph meter; it’s something you’ll be using on a regular basis.
After the first 10 – 14 days of growth, your plants will have consumed most of the nutrients they could extract from the soil, so it’s time to begin feeding them on a regular basis. There is a large variety of nutrient systems (“nutes”) to choose from, either in powdered or liquid form. Liquids are easier to mix with water, but powdered nutes can be a little cheaper to buy, so you should see what works best for you over time.
Fertilizers are basically composed of three substances – nitrogen (N), phosphorous (P), and potassium (K). You’ll find the proportions of each listed on their container in the order N-P-K. For example, a nutrient with the proportions 2-2-1 has equal amounts of nitrogen and phosphorous, each of which is twice as much as the potassium level.
Your plants’ nutrient requirements change as they enter the two different stages of development. During the vegetation stage, plants need higher concentrations of N and P, while during the subsequent flowering (bloom) stage, they’ll need lesser quantities of N and higher amounts of P and K instead.
Organic Earth Juice is just one brand of liquid nutrient that’s easy to use during the vegetative stage. It has a 2-2-1 N-P-K ratio that’s right for plants in this stage. You can also use a two-part liquid nutrient system like the GroTek set pictured here to meet the proper ratios during the different growing stages.
If you can’t readily find these types of high-quality nutrients, you can use more generally available fertilizers found at plant nurseries and garden stores. As long as the N-P-K ratios of the products are appropriate for the growing stage, you can be comfortable using them.
Adding nutrients to your water can change the ph levels of the water. Here’s the order, then, in which you should mix up each batch of nutrients before watering your plants:
- For each clay pot that you’ll be watering, pour about a quart of chlorine-free water into your watering can. (If you’re growing fewer than 3 plants in the pot, you may need less water.)
- Mix the appropriate amount of nutes into it (using the amount recommended on the container).
- Mix well and measure the ph level with your ph meter. If it reads between 6 – 7, you’re in the correct range.
- If not, modify it up or down accordingly by either adding phosphoric acid or baking soda. Once the ph level is correct, water your plants until they’re fairly well saturated.
Water / fertilize them every day following the procedure above. Make sure, though, that the plants’ roots don’t get waterlogged. It’s OK to skip a day of watering occasionally to let the soil dry out a little. If you’re not sure if you’re over-watering or under-watering them, go buy a moisture meter; it will take the guesswork out of it.