Humans often fail at hydrating themselves—and we can tell when we’re thirsty. So, it’s no wonder one of the biggest challenges for plant growers is getting watering right: how, when, how much?
If you’re planning to grow cannabis plants and getting your order of marijuana seeds ready, you may already wonder how you’re going to provide your plants with just enough water.
Can you even overwater your cannabis? What kind of water do you need to use? What’s the best irrigation method for marijuana? Cannabis is a sensitive plant and failing to provide optimal conditions, including adequate soil, nutrients, temperature, and water quality, can result in damaged crops.
We’ve put together this guide to remove all your doubts and help you grow healthy cannabis plants hassle-free.
How much water does cannabis need?
Marijuana is a high-use water plant: grown outdoors, it requires more water than commodity crops like wheat, corn, soybean, or cotton. According to research, a cannabis plant consumes around 22.7l (or 6 gallons) of water per day during the growing season, which takes place from June to October.
On the other hand, indoor cannabis cultivation may require only 2.5-2.8 gallons of water per day per plant towards the end of the growing season. When watering the plant in a pot, make sure the water soaks up the soil completely and wait until it’s almost dry before you add more water.
The amount of water marijuana plants need and watering frequency depend on several factors:
- Temperature. Growing cannabis in warm locations will be different from growing it in northern Europe, for example. In higher temperatures, marijuana plants will require more water, especially during the vegetative and blooming phases. However, warm air is also more humid, so you need to be careful to minimize the risk of mold and fungus developing on every part of the plant.
- Humidity. High humidity climates can be harmful for marijuana and slow down its development. In that case, the plant may require less water, especially in the seedling stage, when it takes in water through leaves. If humidity levels are too low, flushing the plants will help, as well as investing in a humidifier.
- Growing medium. If your plant is growing in a pot, you need to be extra careful to avoid overwatering, which can easily happen when we don’t provide suitable drainage. The roots can “drown” in excessive water and the plant can die. If you’re cultivating cannabis in open soil, you need to make sure all the plants are getting enough water by distributing it evenly throughout the field.
- Growth stage. Marijuana requires different amounts of water at different development stages, as you’ll see later in the article. While the plant is young, it doesn’t require a lot of water and flushing is one of the most common techniques for watering cannabis seedlings. Younger plants also need less frequent watering. However, as the plant grows and reaches the vegetative or blooming phases, it will need more and more water.
- Soil properties. Your way of watering cannabis may also depend on where your plants grow: whether in soil or hydroponic substrates, such as rockwool, clay pebbles, coco coir, and more. These work well with drip irrigation as they allow for more frequent watering without adverse effects. Clay pebbles are also suitable for the bottom of the pot as they help excess water dry out faster.
- End use (fiber, CBD). Depending on why you’re cultivating cannabis, you may plant different varieties of it and grow it in different mediums and conditions, which will affect the amount of water required and the watering frequency. Cannabis varieties grown for fiber can be water-intensive, experts claim.
- Indoor vs. outdoor crop. When cultivating marijuana indoors, you’re able to control the environment more than when growing the plants outdoors. Depending on the climate, you’ll likely need to provide less water for the outdoor cannabis crop as rainfall will partially cover its need for water.
As per watering frequency, cannabis plants, especially young, require watering every two to three days, a little less often in the germination and seedling stages when the water usage is lower.
Overwatering is a common issue in growing cannabis, so unless you’re cultivating it in a very dry environment, make sure you don’t go overboard with water as it can prevent the roots from getting enough nutrients or even cause rotting. It’s critical to get it right from the very beginning—marijuana seeds won’t even sprout without the appropriate amount of water.
When’s the best time to water cannabis?
You should avoid watering cannabis during the day, when there’s a lot of sunshine, because the water evaporates faster and the plants won’t get as much as they need.
The best time to water or spray marijuana is:
- Early in the morning before the sun’s out, or
- In the evening when the sun is setting, especially in warmer months.
This is because the roots retain water better at cooler temperatures. If you’re growing the plants in pots, make sure the pots are protected from direct sunlight and heat to avoid leftover water literally cooking the roots when the sun rises. In winter, avoid watering the plants at night—cold water can damage the roots.
If you’re planning to water cannabis and notice the soil is still wet, better hold on until it starts to dry. Don’t wait until the soil entirely dries out before you water the plants again. To check if the soil is still wet, you can either weigh the pot with the plant and compare it to the usual, dry-soil pot weight, or place a finger in the soil to around 5 cm of depth to determine if the soil is dry enough for a new round of water.
When growing cannabis indoors, the situation is different because you can control different factors affecting the plants, such as temperature or light. Experts recommend watering the plants with the lights off, if possible, because direct light will cause faster loss of water. If not, aim to water the plants under direct light last, and then quickly turn off the light.
Monitor your plants so you can catch any symptoms of thirst early on. This is particularly important if you’re growing marijuana outdoors, where you need to take rainfall into account and plan watering accordingly.
A good way to track dry and wet days and the water you provide to the plants is to use remote-control apps and smart irrigation systems. They can help you ensure the optimal amount of water for your cannabis with no hassle.
What’s the best way to water cannabis?
As your cannabis plants grow, you’ll likely use different methods of watering them. This variety of ways to ensure the plants have enough water enables you to avoid the dangers of overwatering or dehydrating marijuana and making the most out of your crop.
Spraying is the most common way to provide water for young cannabis plants. Their roots are extremely vulnerable at this stage and too much water could damage them. As the roots grow and become more elaborate, they will also become more resilient, but this young stage is where you should be the most careful.
A spray nozzle is better than a watering can, regardless of whether you’re growing marijuana outdoors or indoors. The gentle spray won’t damage the seedling and batter it with a strong water flow.
Manual watering is another common method of providing water for marijuana plants, using cans, bottles, or hoses. You can start using manual watering after seedling, when the plants enter the vegetation stage, as this is when they gradually start to require more water. In this period, cannabis grows branches and leaves and the plants become bigger.
When manually watering your cannabis plants, you will need to add nutrients to the water and ensure it has the right pH and EC levels. Don’t pour all the water at once, but distribute it slowly and evenly around the plant. After watering, there should be runoff water at the bottom of the pot.
Although it requires a substantial initial investment, drip irrigation is a watering method that saves money and time in the long term. Your plants receive water and nutrients through slow, automated drips that ensure every plant gets the right amount of water due to high precision systems and sensors.
By setting up irrigation pipes and drippers for your marijuana crop, you can ensure each plant is watered properly no matter where you are, as many irrigation systems can now be controlled via an app.
Watering cannabis with drip irrigation systems is fast and easy and allows better control over the amount and quality of water your plants receive, and saves gallons and gallons of water in the process.
Other advantages of drip irrigation involve:
- Excellent control, which helps avoid under and overwatering
- Reduced number of hours you have to spend watering and monitoring your plants
- Minimized fertilizer loss
- Better root health
- Reduced energy costs thanks to low-pressure watering, and more.
Ensuring the right water quality for cannabis
When and how you water cannabis aren’t the only aspects of cultivating marijuana that matter. Water quality and nutrients also play a significant role in how well your crop will develop, especially if you bear in mind that water quality depends largely on your location.
For example, even though cannabis can grow just fine using tap water, if water in your region contains a lot of calcium, it can be damaging both for the plants and for your irrigation system. Hard water can leave limescale deposits on leaves and salt deposits in the soil, which prevents the plant from growing properly, especially if in a pot.
Ideally, to water your marijuana plants, you will use:
- Purified RO (reverse osmosis) water
- Tap water that you let sit out to eliminate chlorine
- Collected rainfall
- Bottle water
Cannabis also needs water with a specific pH level: the range you should aim for is between 6 and 7, ideally 6.5 when growing in soil. Water being too acidic or alkaline makes it impossible for cannabis roots to properly absorb nutrients, which negatively affects plant growth and can even kill the plants.
The medium you’re using to grow marijuana can impact the pH levels to aim for. For example, hydroponic growers may need to keep water pH lower, between 5.5 and 6.1. Use a pH meter to measure pH when adding nutrients to your cannabis plants to ensure the best dosage that maintains the ideal pH levels.
Measuring EC levels in water is also important: the harder the water, the higher the EC will be—and it’s not favorable for optimal cannabis growth. Too many chemicals in the water can harm your plants, so you can either:
- Dilute the water you’ve prepared for the crops using rain or RO water
- Let the water sit out for at least 24 hours and wait for EC levels to drop before watering the plants.
Feeding your cannabis with the optimal amount of nutrients
Another concern for inexperienced cannabis growers are nutrients: which ones, when, how much?
Powder nutrients are more common among outdoor marijuana growers, while those cultivating cannabis indoors typically use liquid fertilizer. Cannabis needs: nitrogen, phosphorus, potassium, calcium, and magnesium, along with a few more micronutrients, and carbon, hydrogen, and oxygen extracted from water and air.
How much nutrients your plants will need depends on the soil they grow in, as well as their growth stage. For example, marijuana needs more nitrogen at the vegetative stage, and more potassium and phosphorus while blooming. Marijuana grown in clay pebbles needs to have lower EC levels so you’ll use smaller amounts of nutrients. Always follow the manufacturer’s instructions when adding nutrients to your crops.
If your plants are lacking some of the critical nutrients, you will notice it. Yellow leaves, for instance, can indicate that the cannabis needs more magnesium.But be careful, especially with liquid nutrients. It’s easier to add more if the plants are underfed, than to eliminate the excess that can damage your crops.
If you think you’ve gone overboard with nutrients in water, don’t worry—it doesn’t have to be fatal for cannabis, especially in later stages. Apply the technique called flushing: flush the plants with pH-neutral water to remove excess buildup and get the pH back into balance.
There’s no need to add nutrients to every watering—it’s usually enough to use them every other watering.
Did you know you can use automated irrigation systems to provide your plants with the required nutrients, too?
Symptoms of underwatering cannabis and how to solve them
Although overwatering cannabis is a more common mistake, people tend to underwater the plant, too. Your plants might be dehydrated if:
- They overall look dry and lifeless
- The stem started to bend
- The leaves are turning brown or yellow
- The plant isn’t producing new leaves during vegetative stage
If you notice any of these symptoms in your plants, it may be too late to save them, but you can always try and rehydrate them. Use pH neutral water to help the plant hydrate. No need to add nutrients when trying to recover the plant from being underwatered. When you nurse the plant back to health, you can include fertilizer again.
If the plant isn’t recovering, it’s also worth checking the water pH, as the symptoms of inadequate pH levels may manifest in a similar manner.
Symptoms of overwatering cannabis and how to solve them
Here’s how you can recognize your marijuana plants are overwatered. You may notice:
- Swollen, curled and discolored leaves
- Muddy soil in the pot
You can take several steps to make sure your cannabis isn’t overwatered.
- Use drip irrigation systems to enable each plant to get the exact amount of water it needs.
- If growing marijuana in pots, provide pots with good drainage to avoid the plant getting waterlogged. This will prevent the roots from rotting and the bacteria from accumulating in the soil.
- Stick to a strict schedule to avoid overwatering and don’t get tempted to add more water than recommended based on a gut feeling.
- Monitor water runoff at the bottom of cannabis containers. If the water sits there for too long, it’s time to check drainage and reduce the amount of water used.
Grow healthy cannabis crops with Smart Watering
Smart watering systems ensure better quality crops, saves money and time in the process, and allows better control over your plants no matter where you are as it requires minimal presence.
Technology used in modern irrigation systems also enables real-time data analysis and better insight into your plants’ health and quality, so you can rest assured your cannabis will develop properly and provide a yield you’ll be happy with.
Care to learn more? Our team is here to walk you through every step of the drip irrigation setup process. Book a consultation and let’s have a chat to answer all your questions.