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Stress in Cannabis Plants

Apr 16, 2020
Pruning Techniques

Stress in Cannabis Plants: Types, Causes, and Prevention

Though cannabis is one of the world’s most versatile plants, it can be quite sensitive to environmental factors. During cultivation, growers should know about the stresses and effects their plants may experience. Even our easy to grow marijuana seeds can be subject to natural stressors, so we want to equip you with all the information to make your weed garden a success. In this guide, you’ll learn about stress in cannabis plants and how to manage it effectively.

Plants Experience Different Kinds of Stress

Marijuana plants experience two types of stress: good and bad. While good stress stimulates plants toward thicker and healthier growth, bad stress causes plants to grow slowly and abnormally. If you’re cultivating a crop for personal use, it’s important to learn how to maximize good stress and minimize bad stress.

In the sections below, we’ll discuss some of the worst types of stress in cannabis plants.

Water Stress

Watering a plant like gorilla glue or sour diesel too frequently is just as bad as not watering it enough. Over- and under-watering may lead to a color loss in leaves, causing them to shrivel up and fall off. Over-watering stuffs the plants’ roots, preventing them from absorbing oxygen and nutrients properly. Insufficient watering is a common mistake among beginners. It’s crucial to strike a good balance and work toward consistency.

Nutrient-Related Stress

Like water, nutrients should be delivered in precise amounts to prevent negative stress in cannabis plants. The earliest signs of a nutrient imbalance are seen in a plant’s leaves, which may start turning brown or yellow. Growers should note that, as plants mature, they need fewer nutrients.

Lighting Stress

Cannabis is a challenge to cultivate because of its specific lighting needs. When plants are vegging, they may need up to 18 hours of light. While they’re in the flowering phase, they need 12 hours of light and 12 hours of darkness.

A consistent light schedule is key to the success of a cannabis crop, from marijuana seed to harvest. Turn the lights off and on at the same times each day, and don’t expose the plants to light during times of darkness. Even the slightest bit of light can force plants back into the vegetative phase.

Cannabis plants perceive changes in lighting duration as a seasonal shift, which pushes them into the flowering phase. Additionally, each growth stage requires certain light wavelengths. Many cannabis-specific LED grow lights deliver the spectrums the plants need while preventing heat overload and light stress. Otherwise, various HID spectrums can be used.

Heat Stress

For marijuana plants, excessive heat causes more harm than cold does. If the grow room’s temperature climbs above 85 degrees, the plants will transpire in efforts to cool themselves. This causes stems to grow larger, but the rest of a plant’s growth will be stunted, and yield will be affected. As with lighting and water, the grow room’s humidity and temperature must be consistent and controlled.

Now that we’ve learned about negative stressors, we’ll discuss positive stress in cannabis plants.

Good Stress

As previously mentioned, stress may benefit cannabis plants if it’s introduced properly. Good stress raises a plant’s endurance and makes buds bigger. Clone-worthy plants are those that can survive and thrive on controlled stress. In the sections below, you’ll learn about beneficial stress in marijuana plants.


This method is commonly used to provide plants with measured stress, and some growers do it inadvertently. Using fans to keep leaves and branches in motion causes a small, yet constant amount of stress to plant stems, making them stronger and thicker.

Cold Exposure

Though it may seem extreme, exposing cannabis plants to cold air at the end of the flowering phase may have positive effects. For this approach, bring the grow room’s temperature down to 50-60 degrees during periods of darkness. The shift from warm, well-lit days to cold nights simulates your white widow fem plant’s natural growth cycle and improves metabolism, leading to accelerated resin production.

Low-Stress Training

Low-stress training or LST is a cultivation technique that stimulates branch growth in a certain direction to allow the plants’ lower portions to get more light. When LST is used during vegetation, it makes stems grow thicker. This helps the plants deliver nutrients to the leaves and buds during flowering. Low-stress training keeps plants at a reasonable height, making them bushier, more compact, and easier to grow.

Preventing Negative Stress in Marijuana Plants

If you’re growing medical marijuana seeds for the first time, be prepared for a significant effort. The crop’s health is determined by the growing environment. Factors like lighting, air quality, temperature, and humidity make the difference between a bountiful crop and a poor one.

Bad stress may result in plant hermaphroditism. When a cannabis plant exhibits these tendencies, it may pollinate itself and its neighbors. It only takes one hermaphrodite to ruin a whole crop! If you’re worried about your crop, read on to learn how to prevent negative stress in marijuana plants.

Prevent Lighting Interruptions

Cannabis plants are very resilient and can adapt to various conditions. However, they still need a suitable growing environment. Changes in lighting tell the plants that seasonal changes are coming, and if the lighting schedule and intensity are altered, the plants will suffer undue stress.

This isn’t a major concern for outdoor cultivators because they get the benefit of natural lighting. However, indoor gardens should stay on strict lighting schedules that vary by growth stage. Vegetating plants need 18-24 hours of light, while flowering plants need equal amounts of light and darkness.

Be sure your indoor grow lights offer enough exposure. Putting the lights too close or too far away from the plants will cause stress. When growing marijuana indoors, buds at the bottom of the plants may not get enough light.

Maintaining the Grow Room’s Humidity and Temperature

Cannabis plants will show signs of stress when the growing environment’s temperature is too warm or too cold, and if they’re exposed to high humidity. The difficult part, especially for an indoor grower, is to know the correct humidity and temperature ranges for each growth stage.

  • All weed seeds should be grown with humidity of 65-70% and a temperature of 68-76 degrees. It’s okay to reduce the temperature by five to eight degrees during dark periods. Growing plants need more humidity to ensure that they can take in water through their leaves.
  • During the vegetative stage, lower the room’s humidity level by five percent each week, keeping it between 40 and 70%. The temperature should stay between 70 and 80 degrees. At this stage, plants can absorb more water through their roots, and they cool themselves by evaporating water through their leaves.
  • In the flowering stage, the humidity level can safely be dropped to between 40 and 50%. Keep the temperature between 68 and 78 degrees.
  • Right before harvest, drop the humidity to 30-40% and keep the temperature between 65 and 75 degrees.

If the room’s humidity gets too high, use a dehumidifier and water the plants right after turning the lights on. Increase the humidity level by spraying the plants and using a humidifier.

Reduce the grow room’s temperature by bringing in more air, keeping the lights off during the day, and running an AC unit. Increase the temperature by using larger lights or installing a heating mat on the floor.

Water the Plants Properly

It’s normal for new cannabis growers to water their plants too often. After all, these plants are 80% water, and they need liquid to move nutrients upward. There’s no one-size-fits-all solution because geographical differences determine a plant’s water requirements.

For instance, plants in cooler climates may only need two quarts of water twice per week. In hotter areas, similar plants may need two quarts of water per day due to evaporation. Before setting a watering schedule, check the soil’s drainage by digging a one-foot hole and filling it with water. If the water hasn’t drained in an hour, the soil has poor drainage.

Offer Balanced Nutrition

Nutrient imbalances also cause stress in cannabis plants. Stress may lead to issues such as leaf discoloration and stunted growth. A nutrient excess may attract bugs and other pests that destroy crops when left untended.

Nitrogen, phosphorus, and potassium are the most important nutrients for cannabis. When buying fertilizer, you’ll likely see an NPK ratio on the label. If you’re using high-quality soil, allow the plants to use up the existing nutrients before adding more.

Once the plant opens its new leaves, use a formula with more potassium and nitrogen. As the plants reach the flowering phase, they will need more potassium and phosphorus and less nitrogen. Phosphorus usually increases the number of bud sites and potassium makes buds heavier. If too much nitrogen is used during flowering, bud growth may be stunted, and the product may taste unpleasant.

Bottom Line

Stress can be advantageous and risky when growing marijuanna seeds. When considering external factors such as nutrients, lighting, and watering, it’s important to be consistent and find the proper balance. Professional cannabis growers use stress techniques to make their plants stronger and increase yields, but it should be done with caution. With the right stress training techniques and high-quality seeds from, you’re sure to get a great crop.

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