Watering and Nutrients
When to water you plans - learning good watering practices
It is crucial to know how to water your plants properly. Over and Under watered plants will not grow well and can become sick and vulnerable to pests and diseases. Learning a few simple details can be the difference between a sickly plant and a great plant.
Cannabis plants love water, but they also need plenty of oxygen at the roots so they can grow healthy. The roots can only get the oxygen they need when the growing medium gets to dry out sufficiently between watering. When plants are watered too often, the growing media never gets to dry out and the roots are suffocated from too little oxygen.
When learning about watering it is important to understand that it is not how much you water your plant, but it is how often you water your plant that is most important. As long as the plant has enough time between watering to dry out enough, you can give the plant as much water as the medium can take. (Except in propagation and young seedlings, which haven't grown roots yet.)
The time between watering will vary based on many things. Th heat and humidity of the room, the growth cycle and age of the plant and the growing medium itself, Checking to make sure the medium is sufficiently dry to water again is extremely important. The most accurate way to do this is by using a moisture meter. A moisture meter is an inexpensive analog probe that will tell you how moist the medium is so you will know exactly when to water your plants. It is very helpful because it penetrates deep into the pot to check the moisture content down at the roots, not just the surface of the pot which can dry out quicker.
When watering adult plants always give enough water to soak the entire pot to ensure there are no dry areas deep down where the roots are. You will know when the entire pot is soaked when you see runoff coming out of the bottom of the plant. While it is OK to let a lot of water run through the plant (this is called a flush), you will also be taking out the nutrients in the medium as well so it is best to stop as soon as the water starts to run through. Always make sure you have a drip pan or some way to catch the runoff, you don't want water spilling onto the floor as this can cause mold or mildew which is to be avoided at all costs.
In propagation and young seedlings the growing medium should not be completely soaked because it will never dry out since there are few or no roots, This is the only phase where you should water a little bit more often. Only give enough water to moisten the area around the seed or root tip and water a little everyday during the first week or so.
Cannabis Nutrients
What is N-P-K?
The three basic nutrients that all plants need are Nitrogen (N), Phosphorous (P) and Potassium (K). All nutrients you buy will show the N-P-K value on the label and will identify the level in the mix. Cannabis nutrients are often identified as "Grow" or "Bloom" nutrients The amount of each nutrient needed differs with each grow phase. Vegetative plants like higher Nitrogen levels as this contributes to lush green growth and Flowering plants like higher Phosphorous and Potassium levels as these contribute to flower growth and development.
While there are some nutrients out there with ridiculously high N-P-K values, it is best to stay with more modest numbers so you do not overfeed your plants. A typical Grow blend will be around 6-2-4, while a typical Bloom blend will be around 2-8-10
Macro vs. Micro nutrients
Nitrogen (N), Phosphorous (P) and Potassium (K). are considered Macro Nutrients. Cannabis also needs additional micro nutrients for healthy growth.
The three main micro nutrients are Calcium (C), Magnesium (Mg), and Sulfur (S). These are also essential for healthy growth and can be purchased as an additive to be used when a deficiency is identified.
There are six additional nutrients that healthy cannabis needs in very small doses. These are usually present in sufficient levels in all nutrient blends. These are Boron (B), Copper (C), Zinc (Zn), Iron (Fe), Manganese (Mn), and Molybdenum (Mo). Deficiencies of these nutrients are usually due to incorrect PH and not lack of nutrient in the medium.
Adjusting PH
PH Matters!
It is the single most contributing factor to nutrient deficiencies and other plant problems because cannabis can only uptake nutrients in a specific PH range. For cannabis grown in soil, this range is 6.0 - 7.0. For cannabis grown in Hydroponics, this range is slightly lower, from 5.5 to 6.5.
In order to test and adjust your PH, you will need to get a PH meter. These range from inexpensive to expensive but I would recommend spending the extra for a good quality meter. This meter will be used every time you water and will need to last a long time.
(You cannot use a dye base PH test kit with cannabis because you will also be adding nutrients which would throw the color off, Don't waste your time with these.)
How and When to PH
Always PH your water AFTER you have added all of your nutrients and amendments. Everything you add to your water changes the PH of the solution so it is important to adjust only after everything has been added.
To adjust PH there are products on the market you can purchase called PH UP and PH Down . For a simpler way to adjust, lemon juice will lower PH and baking soda will increase PH.
Take a sample of your solution in a cup and test with the PH Meter. Give it time, sometimes it take a few seconds to adjust. Wait until the reading stops changing.
Add the UP or DOWN additive a little at a time and retest the solution until it gets right into the middle of the range, about 6.5 for soil and 6.0 for Hydro. Be careful, these can be strong and little goes a long way! After a few times you will get to know how much to add to get close.
adding nutrients
Do I Need to Add Nutrients?
The amount of nutrients you use will depend on your growing medium. Super soils that have nutrients added to the soil already will need only occasional feedings in the early phases and more as the nutrients in the soil are used up.. Soil-less mediums like Rock wool and Coco Coir or growing hydroponically will require regular feedings because they do not contain any nutrients of their own.
The key here is to understand that cannabis needs different nutrient levels depending on the growth phase it is in. Adding too much nutrients can lead to nutrient burn and toxicity. Not enough can lead to nutrient deficiencies and sick plants.
Nutrient levels in a water solution are measured by PPM (parts per million). All nutrient formulas will give a recommended amount on the package, but the best way to determine the correct amount is with a PPM Meter. Jus like the PH Meter, these range from inexpensive to expensive but I would recommend spending the extra for a good quality meter.
Nutrient levels by growth phase
Clones and Seedlings 200 - 300 PPM
Vegetative Growth 600 - 800 PPM
Flowering Phase 800 - 1400 PPM
Ripening (flush) 0 - 300 PPM