Cannabis cultivation requires careful attention to the plants environment, including the amount and type of light they receive. Too much or too little light can cause significant damage to the plant, leading to yellowing, burning, or even death.
Light burn and light stress are two common conditions that cannabis growers must be aware of and take steps to prevent. Light burn occurs when the plant is exposed to too much light, causing damage to the leaves and other parts of the plant. Light stress, on the other hand, is caused by a lack of light or improper light spectrum, leading to stunted growth and other issues.
Both conditions can be exacerbated by nutrient deficiencies, making it essential for growers to maintain a careful balance of all factors affecting their plants. In this article, we will explore the difference between light burn and light stress, as well as provide tips for protecting your cannabis plants from these conditions both indoors and outdoors.
Whether you are a seasoned grower or just starting, understanding these conditions and how to prevent them is essential for healthy, thriving cannabis plants.
Causes of Light Burn
Excessive exposure to grow lights beyond the threshold of tolerance can lead to light burn in cannabis plants. This phenomenon is characterized by yellowing of the top leaves directly under the lights, upward-pointing and pale leaves, as well as a more pronounced effect when coupled with nutrient deficiencies. Light burn is often mistaken for a nitrogen deficiency, and if left untreated, it can lead to reduced yields, stunted growth, and even death of the plant.
The primary cause of light burn is the intensity and proximity of the grow lights. High-power LEDs and HPS grow lights are more likely to cause light bleaching than other types of grow lights. Nutrient deficiencies can also exacerbate light burn, making it crucial to maintain a healthy nutrient balance in the soil.
To alleviate light stress, reduce the number of lights or move them further away from the plants. Outdoor plants can also experience light stress if moved from shade to direct sunlight too quickly, so gradual exposure to sunlight is essential.
Symptoms of Light Stress
Symptoms of light stress in cannabis plants are often mistaken for a nitrogen deficiency. Yellowing of the top leaves directly under grow lights, leaves pointing upwards and appearing pale, and buds turning white or appearing burnt are some of the common signs of light stress. Light bleaching is also a common symptom, especially with high-power LEDs and HPS grow lights. This happens when the plants receive too much direct light, causing the buds to turn white.
Nutrient deficiencies can exacerbate light stress, making it crucial to maintain an optimal environment for the plants. To alleviate light stress, reducing the number of lights or moving them further away can help. Outdoor plants can also experience light stress if moved from shade to direct sunlight too quickly.
Heat stress can also mimic light stress, making it essential to maintain a comfortable temperature for the plants’ optimal growth. Supplementing with sea kelp, partially covering, and watering adequately can help protect outdoor plants from heat stress.
Preventing Light Stress
Preventing light stress in cannabis plants requires careful management of environmental factors such as temperature, humidity, and air circulation, as up to 90% of cannabis growers report experiencing some form of light stress during their cultivation process.
To avoid light stress, it is important to monitor the temperature within the growing area and ensure that it remains between 20-26°C. High temperatures can lead to light stress, so it is important to use air conditioning or fans to keep the area cool.
In addition to temperature control, humidity levels should also be monitored and kept between 40-60%. High humidity can promote mold growth and attract pests, while low humidity can cause the plants to become dehydrated.
Good air circulation is also important to prevent the buildup of heat and humidity. Proper ventilation can be achieved by using fans or an air exchange system.
By carefully managing these environmental factors, cannabis growers can prevent light stress and promote healthy plant growth.
Frequently Asked Questions
Can light burn occur with all types of grow lights?
Light burn can occur with all types of grow lights, but light bleaching is more common with high-power LEDs and HPS grow lights. Nutrient deficiencies can exacerbate light burn, so reducing the number of lights or moving them further away can alleviate light stress.
How can you tell the difference between light burn and a nutrient deficiency?
Distinguishing between light burn and nutrient deficiency in cannabis plants can be challenging. However, light burn causes yellowing of the top leaves under grow lights, while nutrient deficiencies affect the entire plant. Monitoring plant growth and considering other factors can help identify the issue.
Can outdoor plants experience light burn even if they are not directly under grow lights?
Outdoor cannabis plants can experience light stress if they are suddenly moved from shade to direct sunlight. This can cause yellowing of leaves and upward pointing, pale leaves, similar to light burn. Adequate watering and partial covering can help alleviate the stress.
What is the best way to supplement outdoor plants with sea kelp to protect them from heat stress?
The best way to supplement outdoor plants with sea kelp to protect them from heat stress is by mixing one tablespoon of liquid seaweed per gallon of water and applying it through the soil or foliar spray. The application should be done early in the morning or late afternoon.
Are there any other types of stress that can mimic light stress in cannabis plants?
Cannabis plants can experience various stress factors that mimic light stress, such as nutrient deficiencies, pest infestations, and high humidity levels. Identifying the specific stressor is crucial to implementing appropriate measures for plant recovery and growth.
