Hell With High Water: The Dangers Of Overwatering Your Cannabis Crop

You might think that drooping leaves means that your plants are thirsty and aren’t getting enough water — but giving them more H2O might actually be doing more harm than good. Much like feeding, the right balance of watering volume and frequency is crucial for healthy plants, especially with young cannabis seedlings.

While many growers carefully avoid underwatering, the dangers of overwatering are equally as damaging, as too much water starves plant roots of oxygen and can weaken them within hours. Though overwatering is a frequent issue for soil growers, hydroponics growers may also face complications (such as the dreaded root rot) when the roots are deprived of oxygen.

Understanding the dangers of too much water, recognizing the warning signs, and knowing the best practices to avoid overwatering are invaluable skills to any successful grow op.

If not treated quickly, overwatering can rapidly deteriorate cannabis plants. Furthermore, overwatered plants are prime candidates for root rot, which attracts subterranean root aphids, as well as mold, a favorite of fungus gnats. Plant pots and containers with improper drainage and oversaturated grow mediums are the biggest offenders, as they keep roots soaking in stagnant water. This suffocates the roots and leads to the first symptoms of overwatering: drooping leaves.

How To Spot The Warning Signs Of Overwatering

Visual cues are the first indicators that your cannabis plants are being overwatered. These symptoms can appear within hours, most often as drooping or pale, discolored leaves. Leaves may take on a pale green, almost yellow appearance, or have burn patterns of discoloration that mimic the symptoms of nutrient deficiency. A powdery mildew may form across the leaves, another sign of too much moisture.

Conversely, leaves that curl at the tips and begin to yellow indicate that the plant is being underwatered. Recognizing the difference between wilting leaves and drooping leaves will determine whether or not a plant is receiving too much or too little water.

Short or undersized plants are symptomatic of overwatering in too large of a container. Plant roots that are unable to absorb enough water in the grow medium are not receiving enough oxygen, resulting in stunted growth. Seedling plants are more likely to thrive in smaller containers where the roots have an easier time taking in moisture from the surrounding soil.

Tactile cues can further diagnose symptoms of overwatering, most notably in the soil. Oversaturated soil remains damp long after watering, making it an ideal breeding ground for mold and insect infestations. Overwatered plants tend to have very moisture-heavy leaves that feel thick to the touch. (Healthy leaves should feel more like a piece of paper between your fingers.)

The sooner you are able to identify and treat the effects of overwatering, the greater the chances of salvaging your plants.

If your roots don’t look healthy and white like these ones, then overwatering could be to blame. Take care to trim the brown sections of roots.

Best Actions To Save Overwatered Plants

When you realize you’ve overwatered your cannabis crop, it’s important to dry out the grow medium and plants as quickly as possible. Start by cutting back on your watering frequency and letting the soil dry almost completely.

Top tip: Seedlings in small containers need more frequent watering with less volume, while larger plants and containers need more water volume but less frequent watering.

Move plants to a new pot with fresh soil. While you should take care not to disturb the roots too much (especially with seedlings), trim off any brown, rotten roots, leaving the healthy, white roots intact. Larger or fabric pots with adequate drainage, like these ones from Smart Pots, filter water more effectively through the grow medium without retaining unnecessary moisture.

Soak up or drain any standing water in drainage trays. Stale or damp air impacts soil just as much as direct watering, so increasing ventilation with an extra fan will help remove any excess moisture in your grow room and reduce the risk for mold.

Extra fans will help remove any excess moisture in your grow room and reduce the risk for mold.

Preventative Measures To Combat Overwatering

While proper watering practices are the best way to ensure your cannabis plants aren’t receiving too much water, there are a few preventative measures that can help encourage better irrigation for your crop.

Preventing the issues associated with overwatering begins with monitoring soil saturation levels by weight, feel, or with a moisture meter. Because a lack of oxygen to the roots is the biggest threat to plants, increasing the airflow and drainage in the soil is key. Adding elements to soil, such as perlite, breaks up the surrounding material, allowing more airflow and better seepage. For growers using soil mixtures as their grow medium, try cutting back on additives like mulch, coco coir or sphagnum peat, as they slow down evaporation and retain extra moisture.

Drying times for soil mediums will vary, so it’s important to check soil saturation by pressing a finger about one inch into the soil (up to the first knuckle). Alternatively, a soil moisture meter offers a more visual indicator of saturation levels. If the soil is still damp four to five days after watering, cut back on watering frequency. If the soil is drying out too quickly, try increasing the watering frequency, aiming for an ideal range of once every two to three days.

Another helpful test is to lift up potted plants to feel the weight. Dry soil is much lighter than saturated soil, and this check can be useful in determining the amount of water remaining in the grow medium. This also will allow any excess water to drain out the bottom of the container and be removed. When watering, aim for about 10–20 percent runoff from your containers. Runoff removes waste byproducts from the soil and signals that the soil is adequately saturated.

The Bottom Line

When it comes to watering your cannabis plants, replicating the natural growing environment is a helpful guideline to keep in mind. In particular, try to limit watering to only when it’s needed, provide sufficient airflow to the plant roots, and eliminate any standing water. After implementing a systematic watering schedule, frequently check soil saturation levels and monitor plants for warning signs of too much moisture. Watering works in conjunction with nutrients during feeding, so methodical watering practices are key to keeping your crop happy and healthy.