There are so many different nutrients for growing weed available that it can be very confusing for beginning pot growers to understand how to select the best nutrients for growing marijuana.
Choosing the best nutrients for weed based on your growing medium
There’s a lot of things to consider when determining the best nutrients for weed grows. The first decision you’ll need to make is what kind of medium you’re growing your pot plants in. Outdoors? Indoors with organic soil and amendments? Soiless mediums such as coco coir? Hydroponics? How to select the best medium for growing weed
Once you’ve determined the way you want to grow, you can narrow down your nutrient options so you can figure out the best nutrients for growing weed with that method.
You’ll need a balanced fertilizer specifically made for weed, these are available in hydro shops and also online if you live in a state where growing is legal. Avoid Miracle-Gro and similar salt-based fertilizers (inclyuding Mircle-Gro bagged potting soil), they won’t do a good job with growing pot plants indoors.
Nitrogen, Phosphorous, and Potassium (NPK)
What is NPK?
Like all fertilizers, the bottles will provide the percentage ratio of NPK (Nitrogen, Phosphorus, and Potassium). The percentage of N-P-K will appear number format such as 10-5-5, which would be 10% Nitrogen (N), 5% Phosphorus (P), and 5% Potassium (K).
How much NPK should be used for weed plants?
Typically marijuana plants need a higher ratio of nitrogen in the vegetation stage, and in the flowering stage they need stronger Phosphorus levels. This is why some manufacturers of weed nutrients offer a “vegetative” and “flowering” version of their nutes.
Often NPK fertilizers used for growing marijuana will come in two separate bottles that should be used in equal amounts, such as Canna Coco A/B. This is because the weed fertilizers can’t be combined together in one bottle without negatively impacting the consistency of the liquid nutrients; both Canna A and Canna B should be added to the water separately and mixed thoroughly in the watering bucket.
Which NPK fertilizer is the best for weed?
There are many growers and therefore many preferences as to the best nutrients for growing weed indoors. Some nutes are much more expensive then others, often a factor in the selection process. As long as you get a balanced NPK fertilizer with a proven track record of growing weed you should be in good shape.
Organic nutrients for growing weed
Organic growers in soil will often add a series of soil amendments to their mix to slowly release NPK.
Organic nutrients for weed are derived from living things, as opposed to chemical fertilizers. You can also use bottled organic nutrients to supplement organic soil additives, this is especially needed if you plant in small containers or vegetate plants for a long time since they’ll start to use up what is in the soil.
Since weed plants’ roots pull in nutrients when absorbing water from soil, these organic nutrient amendments provide nutrition for plants and can also lower the soil PH to a range best for allowing nutrient absorption in soil. Examples of commonly used amendments are organic tea, guano (bat turd), organic compost, etc. Organic nutrients for weed can be used in conjunction with each other to get the best results.
Liquid chemical nutrients for growing weed
Many growers choose to use liquid chemical nutrients for weed. This is especially true when growing hydroponically or in soilless mediums. Growing with hydroponics allows weed roots to absorb their nutrients directly from the watering solution (as opposed to soil grows where the water allows nutrients to get pulled directly from the soil itself).
Using chemical nutrients does give a grower precise control and allows you to adjust for any nutrient problems quickly. But since the nutrients are made available immediately to your pot plants, it can be unforgiving with problems such as pH imbalance or too high PPMs.
Adjusting nutrient solution pH and monitoring PPMs or EC
What is the best nutrient pH?
When preparing a liquid nutrient solution, you’ll need to make sure you properly adjust the acidity of the water and the amount of total dissolved solids (TDS) of the nutrients you add. The acidity or alkalinity of your nutrient water is measured on the pH scale. pH stands for potential of Hydrogen. The pH scale ranges from 1 – 14, with one being the most acidic.
You can use pH Down to lower the nutrient solution pH to the recommended range of 5.5 – 6.5 for coco grows (with 5.8 being ideal) and 6.0 – 7.0 for soil applications. Learn more about the best pH to use with coco coir. Using proper pH allows the plant to absorb the nutrients effectively. The biggest culprit of nutrient problems in weed plants is incorrect pH levels. Getting a decent pH meter is essential for growing weed indoors.
Total dissolved solids (TDS)
The amount of total dissolved solids in your watering solution is also very important. The amount of TDS is measure in PPMs (parts-per-million) or EC (a measure of electrical conductivity). Be aware that there are two PPM scales, 500 and 700. Most PPM meters will allow you to toggle through each of these scales, just make sure that you follow the scale associated with the nutrient feeding schedule you select.
Typically you increase the amount of TDS in your nutrient solution as the plant flowers, scaling back at the end before flushing with plain water right before harvest.
Too high a ratio of nutrients in your water and your PPMs will be too high, resulting in nutrient burn seen by a yellowing of weed leaf tips and edges. Too low PPMs and you’ll start to have nutrient deficiencies. Note that nutrient deficiencies can also be caused by incorrect pH, so always pay attention to both.
Additional nutrients and additives for weed nute solutions
While most most NPK fertilizers for growing weed will have the basic nutrients needed, there are additional chemicals used alongside them. For example the Canna nutrient lines use Phosphorus and Potassium booster called Canna PK 13/14 during mid-flowering to make for P and K available to the pot plants. To correct Calcium (Ca), Magnesium (Mg), or Iron (Fe) deficiencies you can use supplements such as Cal-Mag Plus.
Additional chemicals commonly used when growing weed encourage rooting (an example is Canna Rhizotonic), provide enzymes for proper health within the growing medium (such as Canna Cannazyme), or enhance blooming (Canna Boost or molasses).
The shelves at your local hydro shops are full of options, each one likely proclaiming they are the best nutrients for growing marijuana. If in doubt about the best nutrients for weed in your grow situation, ask for help to make sure you’re covering your bases. Using a packaged product line is a good idea for beginners, once you get a few grow runs under your belt you can start to experiment a bit more.