How And When To Water Your Cannabis Plants 

Watering Cannabis

To grow big, strong and healthy, cannabis plants use a lot of water. The bigger the plant, the bigger the roots and the bigger the roots – the more water they need and consume. Three parameters play a crucial role when it comes to watering – water quality, watering frequency and watering quantity.

Water quality

The biggest and most crucial factor, out of the three, is water quality. Having access to clean and quality water is “a must” for every successful cannabis grow. It doesn’t matter if you’re growing using hydroponics or growing in soil, quality water is needed to ensure optimal health and growth of your cannabis plants.

Outdoors, growers can use fresh water creeks, streams, rivers or lakes but indoors most, especially home growers, that grow a few plants for personal use, are usually limited to their tap water. Unless you have a well or some other reliable water source nearby, your plants will be getting the same water you do.

What may be good for you, doesn’t necessarily have to be good for your plants though. Many water systems filter their water and add various chemicals to it in order to kill possible bacteria, viruses and diseases. Fluoride and chlorine are most commonly used and they both aren’t really good for your plants, especially if you’re growing in “living soil” filled with good bacteria.

Simple method of getting Fluoride and Chlorine out of the water is just letting it evaporate. Chlorine will take about 60-120 minutes while Fluoride may take up to a day or two to evaporate. To get rid of other chemicals that might be in the water, some grower may need to utilize some form of a filter. Most commonly used filtration method is called reverse osmosis, and it gets rid of 95-99% of all dissolved salts in the water. Widely used on a commercial scale, reverse osmosis is an advanced technique that might not be best suited for new growers.

Water pH

By using PH, EC and PPM meters, growers can check and monitor the condition of water they’re using for their growth and can then act and adjust it accordingly, if needed. While any unwanted compounds could be filtered out, to adjust the PH levels growers generally use store bought solutions like PH up/down.

Tap water usually comes around 7.0 PH, which is considered neutral but cannabis likes a slightly acidic water around 6.5 – 6.8. By simply letting the water rest for a few minutes, PH should go down a few notches. If your PH levels are still too high or too low, you can use any product to adjust it – most commonly used by homegrowers and most available are lemon juice and vinegar. By putting a few drops of freshly squeezed lemon juice or vinegar in the water, the PH levels will drop. In some cases, your water can have a lower PH than needed, in which case, aside from the commercially available products, growers can use baking soda – putting a few grams in your water mix will increase the PH.

Adding nutrients will also affect the PH, so make sure that you measure the PH after you’ve mixed your nutrients in. By having your optimal PH levels, you ensure that the nutrients are absorbed in an optimal way and that your roots are at optimal health. Too low PH will cause your nutrients to build up in soil – due to their inability to break down and be accessible and usable to plant, while too high PH may cause your plant to slow down on growth or even be stunted or shocked.

Water temperature

Along with pH and water purity, temperature of the water plays an important role in the end quality of your cannabis too. Having too low or two high water temperature can cause various issues in your cannabis plants. Water temperature is a crucial factor because it dictates how much oxygen is dissolved in the water – which determines the nutrient uptake of the root system and subsequently the overall plant progress and development, resulting in bigger and better yields.

Lower water temperatures often come when you have an outdoor water source, such as a river, creek or a well. Using a reservoir that heats up under the sun will ensure that the temperatures are higher, as well as take care of some of the possible bacteria that could cause harm to your plants.

Lower water temperatures will stunt or shock your plants and roots, causing various nutrient deficiencies, most commonly – phosphorous, magnesium and nitrogen. This will result in poor flower development and smaller leaf and bud sizes – and ultimately lower yield but, in most cases, won’t affect the resin production that much.

Higher water temperatures are not as common but in some climates and setups, especially with automated irrigation, water temperatures can get too hot. Higher water temperatures mean that the oxygen levels will be lower, causing the nutrient uptake to slow down and thus slow down the overall plant development.

Plants develop best with water temperatures ranging between 20 and 25 C and the nutrient uptake is best at 23 C, however cannabis roots develop better at slightly lower temperatures – between 18-19 C, making the ideal temperature for watering cannabis between 20 and 23 C.

How often and how much should you water your cannabis plants?

Most common mistake, especially with new growers, is overwatering. Worried that their plants need constant water and often, as a result of not having something to do on the plants, growers tend to overwater. As much as your plants need water, moisture and humidity they need oxygen too. If roots don’t get enough oxygen, it can make them weak, allowing for much lesser nutrients and water intake and distribution or even suffocate them and eventually kill them off.

Overwatering cannabis comes as a result of too frequent watering rather than watering with too much water. If you use too much water, the excess will simply drain out, leaving you with a flooded floor, in the worst case scenario, but your plants will be just fine, as long as they’re given enough time to properly dry out afterwards.

There are different approaches and methods to watering but the most commonly used one is when you water your plants until you get what’s called a “runoff”. Runoff is just excess water that’s been drained at the bottom. The runoff shouldn’t be significant, as you risk flooding but should exist in order to ensure that no salts or any other compounds are building up in the soil and that all of your soil is properly watered. If you water your plants without having a runoff you risk nutrient build up or lock, also known as root lock. The excess nutrients in the soil will change the soil PH, which will make for some of the compounds to stop being available and may cause deficiency or excess nutrients issues, even when feeding your plants proper doses of nutrients.

It’s important to have good drainage to allow for the extra water to drain out but if you happen to overwater your plants you’ll be able to notice it by slight dropping of the leaves and later even wilting and yellowing, and by general slower or even stunted overall growth. If that happens, you should just let your plants dry out and use less water less frequently.

If your plants start to look fragile, weak with wilting leaves and your containers feel light when you pick them up, those might be signs that you’re not watering your plants enough. Many factors play a role in how fast will your plant use up water – like temperature, humidity, container size and soil composition. Higher temperatures and lowers humidity will force your plant to look for moisture elsewhere in the environment – from their roots. Rapidly intaking moisture from the soil will dry the soil out faster and you may be required to water your plants more frequently. Bigger containers will require more water but will retain moisture for a longer period of time.

If you happen to underwater your plants for a longer period of time and the soil has begun to make a crust, not allowing for proper hydration, just going through the medium to runoff – you’ll need to flush your plants. Flush will ensure that any nutrients build up or lockup is washed away and will properly moisturize your medium.

If flush isn’t needed and as a good practice after the flush, you could water your plants by placing them in a container filled with water, allowing them to intake the water, but from the bottom. Leaving them in for 10-20 minutes and letting them dry out before putting them back will ensure that they’ve had an optimal amount of water. Don’t water again until the top few layers of soil are completely dry.

Watering tips

Letting your medium dry out and allowing for oxygen to go into the roots is vital to ensure for big and healthy roots. By adding perlite, coco, vermiculite and similar compounds to the soil, you’ll both increase the drainage and improve on the water retaining properties of the soil, and allow for better air circulation and better oxygen intake of the roots.

If you use Smart Pots or Air Pots you may need to water your plants more frequently than you would when using regular, potting containers due to better air circulation and more oxygen going to the roots and thus drying the soil much faster.

It’s better to water more frequently but with less water than with more water but less often. When watering, it’s best to give soil time to properly intake the water, sipping bit by bit, slowly, both around the sides and in the center of the container. Taking your time and watering slowly, step by step will ensure that all parts of your soil receive even amounts of water and that your medium is properly hydrated, not just that your water went through the medium.

A good way to determine when your plants need watering is by lifting them up and feeling their weight. You should feel the weight of your plants when watered and before watering to get the feel of it. Once you try it, after a few weeks you should be able to determine pretty accurately if the medium needs watering or not.

To get better oxygen levels in your water and nutrient solutions, you can use air stones, air pumps and oxygen tablets. Best time to water your plants is dusk or dawn and you should avoid watering your plants in the middle of “lights on” indoor period or in the middle of the day outdoors.

Remember: It is illegal to germinate cannabis seeds in many countries including the UK. It is our duty to inform you of this fact and to urge you to obey all of your local laws to the letter. The Vault only ever sells or sends out seeds for souvenir, collection or novelty purposes.

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