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When and How to Water Cannabis Plants

When and How to Water Cannabis Plants

Like all other plants, cannabis needs sunlight, air, nutrients, and water to grow. Though soil is the traditional planting medium, there are several alternatives to consider. Marijuana plants are 80% water, and no matter which growth medium you choose, hydration is the determining factor in the success of the crop.

Many new growers assume that watering the plants is a simple process, but it’s easy to make mistakes such as overwatering. Inexperienced growers often saturate their plants and by doing so block the absorption of oxygen. Underwatering is just as dangerous because when plants don’t get enough water, they begin to wilt. If you’re a first-time cannabis grower, read on for more tips on optimal watering schedules and methods.

What Are the Best Products to Use for Cannabis Plant Hydration?

In the sections below, we’ll provide a list of beneficial products that make it easier to water plants correctly. These products take all the guesswork out of the process and greatly reduce the chances of overwatering or underwatering your plants. No matter which option you select, remember that different growth cycles require unique watering schedules. Here’s a brief overview.

  • During the seedling stage, it’s best to water the plants twice per day and to emphasize frequency rather than volume.
  • In the plants’ vegetative stage, daily watering is best, especially when using small containers. However, if you’re using large pots, water the plants every other day.
  • During the flowering stage, water your plants every two to three days.

As far as container size is concerned, proper selection is crucial to the plants’ adequate hydration. After all, the plant can’t absorb all the water it’s given if the roots won’t reach it! If the plants’ roots don’t absorb all the water, the leftover water provides the perfect breeding ground for fungi, root rot, and insects.

Generally, growers should start off with cubes or pots measuring one square inch in size. As the plants get bigger, increase the container size to four-square-inches, one-gallon, two-gallon, or 3-gallon containers. Each time the plants outgrow their pots, it’s time for a larger size.

Consider Using Smart Pots

Smart Pots are made of canvas, which helps the plants’ roots get the air they need. Breathable canvas also allows heat to escape and water to drain properly, making Smart Pots a popular choice among indoor cannabis growers. Some users believe these pots’ breathability makes them dry out much faster than standard containers. Like anything, there is a learning curve to implementing new growing supplies and infrastructure.

Set Up Drip Lines

If you’re cultivating a large crop or are in an arid, hot climate, drip lines may be a real lifesaver. A drip line system allows for easy watering and even distribution of moisture across each container. For instance, when using perlite, it will rise to the top of the soil if the plants are overwatered.

Additionally, controlling watering frequency and volume makes it easier to control nutrient supply. A drip line system typically includes a range of small droppers and tubes that connect the water supply to every plant in the garden. With a drip line system, you’ll never have to worry about being home to water the plants.

Use Perlite in the Soil

Although perlite is considered an exotic component, it’s becoming more popular among cannabis cultivators. Many gardeners add it to the growing medium because it improves the soil’s structure without affecting electrical conductivity (EC) or water pH.

When this volcanically derived substance is heated to more than 1400° F, it expands, becoming perlite. It’s known for its white appearance, and it can be bought in coarse, medium, and fine grades. If giving plants substantial nourishment, add about 50% perlite to the soil. Reduce levels to 20% if there’s no need to use mass quantities of nutrients and additives.

Think About Soil Type

Whether you’re growing cannabis indoors or outdoors, soil selection largely determines watering schedules. For example, soils in the western United States are much more porous than in other areas, so these plants may need more water to stay hydrated.

Growth mediums retain moisture at different levels. Peat moss, vermiculite, and coco coir all hold water very well. If you’re using one of the above substrates, small-dose, frequent watering may be required. When planning a grow op, be sure to learn about soil types, as they affect the success of the crop.

Buy a Timer for the Drip Line System

When using drip lines, you’ll need a timer as well. Timers reduce the overall level of effort required because the drip system waters the cannabis plants on a predetermined schedule. Once the system is set up on a timer, your plants will be protected from overwatering and underwatering.

Evaluate Other Auto-Watering Systems

We’ve already discussed drip lines, which are a type of auto-watering system. These systems help growers save a great deal of stress and time, and many understand what they’re missing only after attempting to hand-water their plants. Aside from drip irrigation, sprinklers are another viable option. A sprinkler system can be used with a timer to evenly disperse water across the garden.

Though they come with numerous benefits, auto-watering systems have their drawbacks as well. They’re tough to set up, especially for novices, and such systems are often prohibitively expensive for small grow ops. Drip systems require regular inspections and cleanings to prevent clogs, algae buildup, etc.

Furthermore, if the water is dispensed beneath the soil, it’s tough to tell if the plants are receiving enough moisture. If problems arise, they may go unnoticed until the plants show signs of stress. Finally, you can’t just set up the system and forget it. Even with an auto-watering system, it’s important to regularly check the crop for signs of stress, nutrient issues, and/or disease.

How Often Should Plants be Watered for Big, Sticky Buds?

The tips we’ve given so far are relatively broad in nature. Precise watering schedules depend on strain selection, local climate, choice of growing medium, and garden location. Overall, it’s safe to water the plants until the soil is soaked and there’s a bit of runoff. Though the water should stay at the surface for a short while, it should drain down into the soil rather quickly. Be sure to monitor the plants carefully for signs of overwatering or underwatering.

Now that we’ve shown you how to water cannabis plants, we’ll tell you when to do it. When using soil, the plants should be watered as soon as the first inch or two of soil is dry. If the containers feel especially light, it’s time to add some water. Are you using nutrients regularly? If so, add water until 20% runoff comes out of the bottom of the container. This prevents nutrient buildup in the soil, which is the primary cause of nutrient lockout.

Some experts suggest watering plants at night, while other growers do it in the early morning. Once daylight comes or the grow room’s lights are turned on, the plants will absorb water and nutrients, driving photosynthesis and growth.

Learn by Doing

When you’ve learned how to regularly check the growth medium, it’s easier to get a handle on timing and amounts of water required by the plants. At the first sign of wilted leaves, water the plants. Many new growers use watering cans, which aren’t a bad option for those with small gardens. However, once you’ve established a sizable cannabis garden, a watering can won’t provide the required watering volume and efficiency. That’s why many cultivators are turning to battery-operated transfer pumps. These devices make it easy to move water from offsite containers to where it’s needed, and the most common setups pump water from the bottom of three-gallon jugs.

Monitor the pH

Even if you’ve perfected the watering process, low-quality water may undo all that hard work. As most already know, the pH scale goes from 0—14 and determines the alkalinity or acidity of a substance. 7.0 is neutral, and clean water should be at or around neutral. Cannabis plants’ ability to take in nutrients is determined largely by the pH of the water they receive. 0-6.9 is considered acidic, while anything above 7.1 is alkaline.

Through years of experimentation, cultivators have determined that cannabis grows best at a 6.5 pH. It’s easy to measure pH by testing a water runoff sample. This testing method is preferred because runoff has already gone through the growth medium and left the container. If the water’s pH is too low or too high, you’ll need to use supplements to get it closer to 6.5.

Avoid Root Rot, Edema, and Other Problems

When plants receive too much water, edema may set in. Here, the plant’s cells swell and eventually rupture. In such cases, scar tissue, lesions, and leaf indentations may be visible.

When the growth medium is always saturated, the plants’ roots will suffocate. As they’re deprived of oxygen, they’ll begin to rot. Root rot is a fungal disease that infects plants’ roots, turning them slimy and gray. If a plant is infested with root rot, remove it from the garden to prevent the disease from spreading.

Treating Underwatered Plants

Underwatering is simple to fix; just give the plants more water. However, a prolonged case may do substantial damage to the crop. When plants are near death, it’s almost impossible for them to recover. If you’re trying to nurse them back to health, don’t use enriched water. Rather, use pH-balanced water to rehydrate the plants. Once they’ve stopped wilting and have returned to normal, it’s safe to resume a regular feeding schedule.

Look at Your Lighting

Upgrading the grow room’s lighting system midway through a growth cycle may stress the plants. For example, if exposure is increased or the lights are brought closer to the plants, the crop may suffer from underwatering. After all, when cannabis plants receive more light, they’ll also need more water.


PPM or parts per million is a measurement of the level of minerals in the water the plants are receiving. For example, a reading of 115 ppm indicates that there’s 115mg of minerals per liter of water. During the plants’ vegetative stage, 500 is an ideal PPM reading; that number increases to 1000 during the flowering phase. With a TDS meter, growers can test the water they’re using and ensure that the plants are getting the right level of nourishment.

Water Quality

Not all growers are lucky enough to live in areas with high-quality groundwater. If you’re in an area where the water quality is less than desirable, the water your plants are getting may be full of bacteria and other contaminants. Trying to cultivate cannabis under these conditions is a recipe for disaster. To minimize the chances of crop loss and to avoid wasting effort, money, and time, invest in an RO or reverse osmosis filter. RO filters remove about 99% of dissolved solids within the water, providing the plants with the cleanest hydration possible.

Water Temperature

Along with all the other considerations a cannabis cultivator must make, water temperature is another crucial component of a successful crop. The perfect water temperature for cannabis ranges from 68 –  73 °F. If the water is too cold or too hot, the plants’ roots won’t absorb nutrients.

Closing Thoughts on Proper Cannabis Plant Hydration

If you’ve never grown cannabis before, you may be surprised at the level of effort required. Cultivation involves more than planting seeds, adding fertilizer, and watering the plants occasionally. For a strong, healthy crop, it’s important to look at the finer details.

Proper watering is one of the most important steps to take, but it’s not as simple as filling a watering can. When setting the garden’s watering schedule, it may be necessary to adjust it based on location, climate, and other factors.

Finally, you’ll have to consider the method of watering. Small gardens can successfully be watered with cans, but those with larger grow ops should consider investing in an auto-watering system. Automation takes much of the stress out of cannabis cultivation.

Wherever you’re at in your process as a cannabis cultivator, a steady supply of seeds is available to be shipped to your door from Seeds can be saved for three to ten years, so acquiring seeds now means you’ll have a seed supply once your watering system is in place. Check out the seed catalogue today!


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