Deal With Heat Stress in Weed Plants


Esteban Lopez via Unsplash



Are you wondering why your marijuana plants are turning brown? Heat stress in weed can cause discoloration and other adverse effects. 

How do you resolve this issue and ensure your crops are healthy? Plant White Widow feminized  seeds or similar strains that are heat and disease-resistant. 

Understanding the causes of the condition and how to solve it is imperative. Keep scrolling to discover how to identify and prevent this problem in your weed garden. 

What Is Heat Stress in Cannabis Plants?

The ideal temperature for cultivating cannabis plants is 70–800F during the day and 50–600F at night. Depending on the strain and growing stage, it can be slightly lower or higher.

Too high a temperature for an extended period may lead to heat stress in cannabis plants. This condition prevents the plant from sustaining stable internal conditions. 

Heat stress may occur during any phase of the crop’s life cycle. 

Symptoms of Cannabis Heat Stress

Grow cannabis like a pro by understanding the signs of this condition. Heat stress may occur during any phase of the crop’s life cycle. The symptoms may vary depending on the growth stage of the weed plants.

1. Stunted Growth

Heat stress in the seedling phase reduces the plant’s ability to absorb nutrients necessary for growth. 

In severe cases, it can damage the young roots and slow the seedlings’ growth rate. These crops won’t reach their ideal height unless the issue is corrected.

2. Withering Leaves

The new seedlings’ leaves can wither if there’s too little water in the soil. Heat or light stress may also contribute to this symptom. 

This issue may also occur in the vegetative or flowering phases. Take swift action so that the affliction doesn’t impact your harvest.

3. Curled Leaves 

Placing the light source too close to the plants can cause heat stress during the flowering stage. It can result in leaf edges curling up and taking on a taco shape. 

The leaves turn yellow and brown if you don’t correct the issue. The tips appear dry and burnt. 

4. Cannabis Foxtailing 

Another telltale sign of heat stress is the development of irregular buds on top of the mature ones. 

Light bulbs with high intensity or excess heat are among the leading causes of foxtailing during the flowering stage.

5. White Pistils

Female cannabis plants develop white pistils, which turn orange or pink in the mid or late-flowering stage. 

Light or heat stress in the weed crop can prompt it to continue developing the white pistils. 

6. Spots on Leaves 

Overexposure of marijuana plants to sun rays or indoor bulbs can cause light burn. This condition causes the leaves to form brown spots. 

Light burn usually affects the top leaves since they’re closest to the bulb. 

Causes of Cannabis Heat Stress

Now that you understand the cannabis heat stress symptoms, you might be curious to know the causes. 

The main factors contributing to this condition: 

Too Much Light 

Weed plants require light to carry out essential processes like photosynthesis. If there’s too much, it can cause heat stress. 

Placing the light source very close to the crops exposes them to excess intensity. High PPFD (photosynthetic photon flux density) levels, over 1300–1500, can damage the plant tissue and cause leaf burn. 

High-intensity discharge (HID) bulbs may also emit excess warmth that causes heat stress on cannabis plants.

Low Humidity 

The growing area becomes too dry when relative humidity falls below the ideal 50–60% range. The plants lose water via stomata (leaf pores) in these conditions. 

The growing medium also loses moisture through evaporation, making the crops display signs of heat stress. 

Environmental Factors

High temperatures cause the crops to lose moisture via transpiration. Poor ventilation prevents cool air from penetrating your growing room, leading to heat buildup. 

The conditions can become too hot if you grow weed outdoors, causing cannabis heat stress. 

How to Prevent and Fix Cannabis Heat Stress 

Managing heat stress symptoms depends on whether you’re growing the crops indoors or outdoors. Cultivating outside can be challenging as you can’t control climatic conditions. 

Overcome this disadvantage by selecting the best weed seeds suited to your area’s weather. 

How to Solve Cannabis Heat Stress Indoors 

Will plants recover from heat stress? Yes, if you take action quickly. Follow the tips below to help your weed plants. 

The best way to prevent the issue in your growing room is to invest in quality equipment like light bulbs, air conditioners, and fans. These items allow you to provide the plants with the best conditions for optimum growth. 

If the temperature is too high, use the air conditioning unit to lower it to the ideal level. The fan can also help kick out some of the hot air. Increasing the distance between your light bulbs and plants may reduce heat stress risks. 

Other tips for solving marijuana heat stress in weed plants indoors include: 

  • Upgrade to light-emitting diode (LED) bulbs that emit less heat.
  • Invest in high-quality fans that promote a complete air change every four or five minutes.
  • Water the plants frequently to avoid dehydration. 

How to Solve Cannabis Heat Stress Outdoors 

Solving heat stress outdoors requires creativity compared to indoor options. With the latter option, you can easily control your home’s microclimate.

The best ways to fix heat stress outdoors include:

  • Don’t grow weed in black containers that absorb excess heat.
  • Plant in containers you can transfer under shade when the sunlight is too intense.
  • Apply kelp and seaweed to prevent nutrient deficiency.
  • Erect a shade over the marijuana plants to avoid heat-stressed buds. 
  • Research your area’s climate and plant when the outdoor conditions are favorable.
  • Use large containers that retain moisture for longer. 

Keep Your Cannabis Plants Stress-Free 

Cultivating weed at home doesn’t have to be challenging. Maintaining the right conditions for your plants keeps them stress-free, healthy, and productive. 

Select the best marijuana seeds and apply the above tips. Relax and observe as your cannabis crops flourish, whether you grow indoors or outdoors.

Kyle Kushman

Kyle Kushman is an American writer, educator, activist and award-winning cannabis cultivator and breeder specializing in veganic cultivation. He is a representative of Homegrown Cannabis CO company, has been a contributor for over 20 years, and has taught courses in advanced horticulture at Oaksterdam University in Oakland, California and across the United States. Kushman also hosts a cannabis podcast called “The Grow Show with Kyle Kushman”.

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