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How to Grow Marijuana Hydroponically

Last Updated: October 8, 2020 References Approved

This article was co-authored by Lauren Kurtz. Lauren Kurtz is a Naturalist and Horticultural Specialist. Lauren has worked for Aurora, Colorado managing the Water-Wise Garden at Aurora Municipal Center for the Water Conservation Department. She earned a BA in Environmental and Sustainability Studies from Western Michigan University in 2014.

There are 15 references cited in this article, which can be found at the bottom of the page.

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Whether you call it weed, cannabis, pot, marijuana, or something else, the plant known as Cannabis sativa is actually easy to grow at home when you know what you need to do. Growing hydroponically will provide you with higher yields and a shorter grow time compared to growing in soil, but it can often be difficult for the beginning grower to get started with hydroponics. However, most people think of plants growing in water when they think “hydroponics” but actually your plants will get many of the benefits of hydroponics as long as they’re getting their nutrients directly in their water supply. However because of superior air to water ratio in hydroponics, it remains the industry standard. This tutorial will show you step-by-step how to grow your marijuana in 3-4 months using the (arguably) easiest hydroponic method: hand-watering in a soil-less medium.

How to Grow Marijuana Hydroponically. Whether you call it weed, cannabis, pot, marijuana, or something else, the plant known as Cannabis sativa is actually easy to grow at home when you know what you need to do. Growing hydroponically will…

How To Water Cannabis Plants: A Comprehensive Guide

Your cannabis plants need water in order to thrive. Seems simple enough, doesn’t it? But did you know that incorrect watering is the most common reason for plant health issues? Learn how and when to water your plants so you can avoid any problems before they have a chance to happen!

Contents:

Watering cannabis plants seems like the easiest thing to do, yet many growers, especially those new to cannabis cultivation, make mistakes with watering. Overwatering is one of the most common reasons for all sorts of growing troubles such as nutrient deficiencies and cannabis diseases, although giving your plants too little water can also negatively affect their growth.

HOW MUCH SHOULD YOU WATER CANNABIS?

One issue with watering plants is that it isn’t really an exact science, and many different factors contribute to how much you should administer. As an obvious example, as your plants get bigger, their watering needs will change. But there are other, more complex variables that also determine how much or little you should drench your plants. Let’s discuss some of the most vital:

STAGE OF GROWTH

Cannabis plants have different watering demands depending on their stage of maturity. The specific guidelines we share below apply to mature vegetating and flowering plants. Seedlings and clones require much less water.

In the early stages, avoid watering your plants with a powerful stream that might knock them over and disturb developing roots. Instead, use a light mister to gently moisten the substrate.

Wait for the soil to dry out completely before repeating the procedure. How quickly the soil will dry will depend on your environmental conditions, but this roughly translates to misting once every 2–3 days.

GROWING MEDIUM

The type of growing medium you use largely determines how much water the soil can hold, and drainage plays a huge role in how often/how much you water your plants. Cannabis likes rich yet airy and “fluffy” types of soils that are well-draining. As another consideration, the growing containers themselves must have holes punctured in the bottom to allow the water to escape. More compact soil mixes will hold moisture much longer, so they require less frequent watering as a result. Otherwise, moisture can linger in the soil for some time, which can lead to nutrient deficiencies, root rot and fungus, pests, and a whole lot of other problems.

Here is a quick way to check if your water is draining properly: If it takes several minutes for water to drain after drenching the soil, and/or if it takes longer than 3–4 days for your soil to dry out, it’s likely that you have a drainage issue. Even if you don’t see adverse symptoms now, it could definitely lead to more problems down the line. In this case, you can add perlite or something similar to your soil to aerate the mix and improve its drainage ability. Perlite ensures that water doesn’t stay too long in your pot. The key to good soil for cannabis plants, whether store-bought or homemade, is to balance moisture retention with water drainage. This usually means soil that is dark and rich, but amended with perlite and/or other substances to promote a healthy and efficient medium for plants to grow.

SIZE OF CONTAINER

Then of course, the dimensions of your container will also affect the overall balance between moisture retention and drainage. If you have a tiny plant in a huge pot, drenching the whole substrate is going to drown the poor thing before it gets a chance to flourish. Similarly, you might experience the opposite issue with huge root-bound plants stuck in minuscule pots. This is also the reason that growers normally start seedlings in smaller pots, then up-pot them later as the plant grows. A small seedling pot makes it much easier not to overwater the sensitive seedling.

OUTSIDE TEMPS AND LIGHT INTENSITY

Cannabis plants don’t always grow at the same pace. A plant in a cooler environment, for example, will grow much slower than one under balmier conditions. Light intensity plays another big role here. Plants that receive more heat and light are bound to have higher water and nutrient requirements than those with meagre light and chilly temps.

HEALTH OF CANNABIS PLANTS

The general health and vitality of your plants will also determine how much water they require. If growth is slow or stunted, or if a plant is afflicted with diseases or pests, it will likely not need as much water as one that is thriving.

HOW TO TELL IF YOUR PLANTS ARE THIRSTY

You now know about the factors that determine how much and how often cannabis plants need water, and how these factors can be different for everyone. So now, how can you tell exactly when you should water?

Here are some signs that your cannabis plants are thirsty:

DROOPING, WEAK PLANTS

If your cannabis plants are very thirsty, they will droop. The whole plant will appear rather sickly and lifeless, so it’s difficult to overlook this sign. One catch here though is that thirsty plants can look very similar to those that are drooping because of overwatering. The difference here is that the leaves of overwatered plants are usually dark green and form a “claw” where they curl and bend downwards, so the whole plant takes on a heavy and waterlogged appearance.

If you’re somewhat experienced, you should be able to tell these conditions apart. Most of the time, it should be obvious if the drooping is from over or under-watering: If the soil is bone-dry and you know you haven’t watered in quite some time, the sickly appearance of your plants is less likely from overwatering.

Tip: Know that slightly underwatering your plants is always better than overwatering. If you water thirsty, otherwise healthy plants, they should normally recover their appearance in a couple of hours. Occasional underwatering doesn’t usually have harmful consequences. Overwatering, on the other hand, is a silent killer.

YELLOW OR BROWN LEAVES

Along with your thirsty plant wilting and drooping due to a lack of water, it may also display discoloured leaves in shades of yellow and brown. While it is perfectly normal for plants to develop yellow leaves during the final weeks of bloom, a healthy vegetating plant shouldn’t have any/many dry, yellow, or brown foliage.

JUST CHECK THE SOIL!

Take the guesswork out of your watering routine with a simple method. Placing the tip of your finger into the top 5cm of soil provides a good indicator of how dry the upper soil has become. However, it won’t allow you to detect the water content of the middle and bottom of the growing medium.

Weighing your pots instead will give you a clear picture of how much water remains. You can operate based on a general feeling of how your containers feel in your hands when they are dry compared to when they are saturated. Even better, weigh them to know exactly when they’re ready for some more H₂O.

HOW TO WATER YOUR CANNABIS PLANTS

Here is a simple rule: Water less, but water well! Rather than giving your plants a little bit of water often, treat them to a healthy, less frequent soak. But how much water is sufficient?

A good soak means watering the medium to 25–33% of the pot capacity. This amount of water will provide the root system with all it needs, without causing pooling and potential fungal issues.

When watering, aim for the middle of the substrate first. After letting the roots breathe, water the edges of the container too. This approach will encourage the root ball to reach to the edges of the pot, and also shuttle nutrients sitting in the top of the medium down to the root system below.

This method will deliver the correct amount of water, without creating pools in the substrate. Excess water creates a humid environment—a perfect breeding ground for fungal pathogens that lead to root rot.

DON’T LEAVE YOUR PLANTS SITTING IN RUNOFF

Along with your containers featuring holes at the bottom for water to escape from, the containers themselves should be lifted slightly off the ground so that all the water can drain and plants aren’t sitting in stale liquid. Drainage trays can catch this runoff, but should immediately be dumped after collection to avoid creating a breeding ground for bacteria, pests, and mould.

THE IMPORTANCE OF PH WHEN WATERING PLANTS

If you are growing cannabis organically in soil, you shouldn’t need to worry much about the pH level of your water/nutrient solution. But for the majority of cannabis growers who are using common mineral nutrients and grow weed in soil, coco, or hydroponically, the correct pH level of the water is very important.

The reason for this is that cannabis plants have a limited pH window where they are able to take in nutrients. If the pH level of the water is either too high or too low, the plants are unable to take in nutrients even if they are present, a phenomenon known as nutrient lockout.

When you grow in soil, the pH range of your water should be 6.3–6.8. If you grow soilless (e.g. coco) or hydroponically, the pH level needs to be even lower, 5.5–6.1. To test your water pH, use a pH measuring stick or pH measuring drops. If the pH is too high or too low, use some drops of “pH down” or “pH up” to adjust your water to the right level. Most of the time, if you’re using tap water, your pH will likely be too high.

Also, if you’re adding cannabis nutrients to your water, measure the pH after each feed. This will give you accurate data of how you have influenced the soil. It will also let you know if you need to add more nutes, or modify the dose during next feed.

BOTTOM LINE—WATER WELL, BUT NOT TOO OFTEN!

If you know how and when to water your plants, and are aware of any associated issues along the way, you can prevent most common cannabis growing problems. You will raise happy, healthy plants, and can look forward to fantastic yields!

The HI-98107 pHep pH tester provides fast and accurate pH readings. The easy-to-use device is designed for non-technical users, and can help both novice and advanced growers measure water pH.

HI-98107 pHep pH tester provides fast and accurate pH readings. The easy-to-use device is designed for non-technical users, and can help both novice and advanced growers measure water pH.

Click here to find out everything you need to know about how and when to water cannabis plants. Watering may seem easy, but many growers still get it wrong. ]]>