How to Water Your Cannabis Plants

Freshly Watered Plants

How to Water Your Cannabis Plants Properly

First, we need to talk about the types of water you can use to water you cannabis plants.

What Type of Water Should I Use?

There are a few types of water you can water your cannabis plants with.

  • Distilled water
  • Rain water
  • Tap water (left out for at least 24 hours)
  • Reverse osmosis water

Distilled Water

This is water that is purified by evaporation and condensation. This removes any impurities and minerals from the water. If you use this, you’ll need to add supplemental calcium & magnesium. Distilled water is great for controlling your ppm as it starts at virtually zero. Although, using only distilled water to water your plants and fill your humidifier can get pretty costly.

Rain Water

Using rain water has several benefits over tap water. It doesn’t contain any chlorine or fluoride that is added to the tap water. Rain water also contains less magnesium and calcium concentrations than harder tap water. It also saves you on the cost of water. You will have to buy a rain barrel to collect the rain, but it is a small investment (roughly $50CAD). You may want to add some supplemental calcium and magnesium if you’re using rain water, but it does contain some already.

Tap Water

If you use tap water, you need to let it sit out for at least 24 hours. This allows the chlorine to evaporate out of the water. You also need to find out how hard your water is. You can usually find out on your city/town website if they have one. You can also contact your local water treatment company to find out the mineral profile of your water. If your local water is soft enough, you can use it without any filtration. You may want to add some supplemental calcium & magnesium, depending on the levels in your water already.

Reverse Osmosis Water

Reverse osmosis is a water purification process that uses a semi-permeable membrane to remove unwanted particles, ions and molecules. This is used to purify hard water which contains higher concentrations of magnesium, calcium and other dissolved minerals. This requires the purchase of a reverse osmosis filtration system. Unless you need one for your drinking water, I don’t recommend buying it solely for your plants. You will need to add supplemental calcium & magnesium to your RO water.

Regardless of the type of water you use, it is always important to pH balance your water before giving it to your plants. Always do this step last because liquid fertilizers and additives can effect the pH.

How Often Should I Water My Plants?

When it comes to watering your plants, you should always check the soil before watering. You should do the knuckle test. Simply, put your finger into the soil up to your first knuckle or about an inch deep. If it’s wet or moist, let it dry out for another 12-24 hours before watering. If it’s dry, it’s time to water the cannabis plants. If you’re using coco coir, the top inch doesn’t have to dry out completely. You should aim to water the plants every 1-2 days. But, don’t water if the top inch is still wet. If your medium stays wet for 3+ days, adjust the amount of water given at each watering. If it takes 5+ days to dry out, then you may have an issue with drainage.

To prevent drainage issues:

  • Mix in extra perlite to allow better drainage
  • Use smart pots, air pots or fabric pots to promote oxygen at these plants roots; These pots also helps prevent overwatering

If you’re adding liquid fertilizer to your water on a regular basis, you should water until you get a decent amount (about 10%) of runoff in the tray. This ensures that you don’t get a buildup in the soil of nutrients. You can simply suck up the excess runoff up with a shop vac. If you are using super soil or heavily amended soil, you want to avoid any runoff. Otherwise, you’re losing some nutrients in the runoff.

How Much Water Should I Give My Plants?

When watering your plants you should make a small perimeter around your plant. With very young seedlings, I use a spray bottle to water them because they don’t require much water at that stage. I’ll spray them between 2-4 times a day depending on the humidity in the tent

Once they get a little bigger, I use a sports water bottle to water them because they require a little not more water as they grow. I will water them like this about once a day.

Once they are bigger, you can gradually increase the amount of water a little bit at a time. You add a little more water each time the plant grows larger. When the plant gets to be about a foot high, you can water it with roughly 1 liter at a time. By the time they are large plants, they can get watered roughly 1.5-1.75 liter at a time. You will have to experiment with the amounts as you grow, but once you get the hang of it, it comes second nature.

If your plants are drying out everyday or multiple times a day then you should consider transplanting into a bigger pot or increasing the amount of water. If you start your plants in solo cups, you should transplant them after approximately 1 week or when the leaves extend past the cups edge.

Collecting Rain Water for Your Cannabis Plants

Using rain water (or snow) for your plants can help save you money while also benefiting the plant as well. It’s what plants get in nature as their water source, so why not mimic nature. 

Why Use Rain Water for Your Plants?

Whether you put your plants out to get the rain or collect the rain water to be used later, the benefits are the same. In nature, rain is the main source of water so it makes sense to use what plants naturally are used to. You can also use collected snow in the winter, but be sure to let it melt and reach room temperature before watering plants. There are a few key reasons to use rain for your plants though.

So, let’s dive right into it.

It Saves Money

Collecting rain water doesn’t cost anything and you can store it for later use. In contrast, tap water, distilled water and reverse osmosis water all have some degree of cost to them. So using rain water can save you some money. Who doesn’t like that!

It Contains More Oxygen Than Tap Water

The air is made up of 78% nitrogen so it will help plants to look more lush and green. The rain water is highly oxygenated in comparison to tap after or distilled water. This helps to prevent over watering issues such as anaerobic conditions which can lead to root rot.

It Helps Release Micronutrients

Carbon dioxide comes down with the rain and mixes with other minerals in the atmosphere. This creates a slightly acidic rain that when it touches the soil helps to release micronutrients such as zinc, manganese, copper and iron. *Not to be confused with actual acid rain which will harm your plants.*

Less Chemicals Than Tap Water

Tap water needs added chlorine or chloramine as a disinfectant and some municipalities also add fluoride to the water for cavity prevention. If given to plants, it can cause toxicity, which basically means an excess of that nutrient. This excess can cause damage to your plants in various different ways. For example, chlorine toxicity can cause yellowing, browning or scorched looking leaves. Additionally, the chlorine or chloramine in tap water kills the beneficial microbial life in your soil or coco coir.

Tips for Gathering Rain Or Snow

You can use almost anything to collect rain water such as tupperware, bucket or even cups if you had nothing else. You can also use a rain barrel to collect water. This is a great idea if you can your hands on one. Simply set it up to drain from your eavestrough directly into the barrel. Once it’s full enough, you can put the water in gallon jugs for storage. If you’re collecting snow, you’ll want to let it melt and get up to room temperature before giving it to your plants.

Snow Flush

You can also do a snow flush on your plants before harvest to simulate the colder, winter weather approaching. Simply add some snow to your soil and let it melt and water the plants. This stimulate nature and helps signal to the plant that it’s time to finish up.