As much as cannabis is resilient, growing the plant is challenging, especially to first time and some experienced growers. You can have your crops looking good at one time but come the following day, they exhibit damaged leaves due to cannabis heat stress, even after following all the required schedules of lighting, feeding, and watering correctly.
Cannabis plants need heat for their healthy growth and proper development. However, too much heat causes stress leading to improper plant development and growth, leading to poor and low-quality yields.
Cannabis plants also need stable temperature levels for faster root development and overall growth. Seeds may not germinate, and the plants will not grow if the grow room is too cold. You should always maintain the right temperatures to prevent stunted crop growth, especially at night, for abundance yields with strong stems and leaves.
While maintaining the right temperature levels to avoid extreme cold situations, you should be careful not to feed your cannabis plants with too much heat because that will lead to disaster. It is possible to prevent the destruction of heat stress causes to the plants by maintaining the correct light balance, among other things.
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Signs of Heat Stress
Identifying cannabis heat stress is easy as the telltale signs are visible, with the leaves being the first casualties. When exposed to heat stress, the leaves take a withered and dry look, with the ends curling upwards just as they do in the case of overfeeding. However, in overfeeding, the whole leaf curls, whereas heat stress causes only the ends to curl.
Other signs include blotches and spots manifesting themselves on the leaves in irregular shapes and yellow discoloration patches. The leaves mostly affected by heat stress are those around the plant perimeter and those at the top of the canopies because they are directly under the lights or too close to the lamps.
Low humidity in the grow tent or arid climate locations is also a major cause of the heat stress of cannabis plants. Plants growing in these circumstances are susceptible to cupped leaves and leaf discoloration. The heat may not seem too harsh, but you can only expect destruction on your plants once it combines with low humidity.
Some growers grow their crops in low humidity places to prevent top rot, but once they forget to keep heat levels stable, the leaves start changing due to stress. During the cannabis life cycle, the flowering phase gets the brunt of heat stress much more than other phases. Plants are at their peak growth during this stage, with many reaching their maximum heights, reducing the distance between the canopies and the lights.
If you fail to keep a good distance between the flowering plants and lights, overheating damages the leaves. Once this happens, you will end up with buds with much lower potential than anticipated. The abnormal bud formation manifests in foxtailing, which occurs due to the buds’ proximity to the grow lights.
Unnecessary light during the flowering phase also leads to buds displaying new growth at the top at much higher rates than they do with the bottom buds at the bottom. The appearance becomes a problem because it leads to the formation of white pistils that give the assumption that the buds are not ready for harvesting.
The appearances are also a sign of overheating. If this happens, look at the bottom buds’ appearance to make a better decision on whether the buds are ready for harvesting or not since they provide the best maturity signs.
Read next: How To Detect And Treat Cannabis Light Burn
Managing Heat Stress Indoors
Regulating indoor temperatures is challenging, especially to growers that live in low humid and hot/dry climates. Summers in these places are not easy to deal with because you have the natural heat and heat from the grow lights.
Even those that live in places with much friendlier climates still find it challenging to regulate lighting levels in grow tents. However, with the following adjustments and grow tent improvements, you van avoid cannabis heat stress from affecting your plants.
Use fans
Using fans in the grow room is the cheapest and simplest solution to preventing heat stress. Fans create a convection current in the grow space that disrupts hot and still air for a cooler growing environment. The cool air stresses the plants helping them grow with strong and thick stems.
- Designed to ventilate hydroponic grow rooms, transfer heating/cooling, cool AV closets, and exhaust odors.
- Dynamic temperature and humidity programming, with timers, grow cycles, scheduling, minimum speed.
- Connect with our app via Bluetooth to access advance programs, alarms, notifications, and view climate data.
- Mixed flow design combined with a PWM-controlled EC-motor for a truly quiet and energy efficient performance.
- Duct Size: 6” | Dimensions: 7.9 x 12.6 x 8.4 in. | Airflow: 402 CFM | Noise: 32 dBA | Bearings: Dual Ball
- Designed to ventilate hydroponic grow rooms, transfer heating/cooling, cool AV closets, and exhaust odors.
- Dynamic temperature and humidity programming, with timers, grow cycles, scheduling, minimum speed.
- Connect with our app via Bluetooth to access advance programs, alarms, notifications, and view climate data.
- Mixed flow design combined with a PWM-controlled EC-motor for a truly quiet and energy efficient performance.
- Duct Size: 4” | Dimensions: 6.9 x 11.9 x 7.4 in. | Airflow: 205 CFM | Noise: 28 dBA | Bearings: Dual Ball
- Perfect Combination: Three-part system includes every part you need to get set up; It is primarily used in various air circulation and ventilation projects to move and transport air
- Energy-Efficient Ventilation: The inline duct fan helps solve ventilation problems; This fan is durable and runs smoothly and quietly; Variable speed controller facilitates fan speed adjustment
- Excellent Odor Control: The porous activated carbon with 1050+ RC 48 Australia Virgin Charcoal helps eliminate some of the most undesirable, pungent smells and particulates for indoor grow tents
- Perfect Connector: The VIVOSUN ducts are made of high-quality aluminum; Features a double layer of protection with PET thermoplastic; Comes with two heavy-duty stainless clamps
- Cost Effectiveness: This combination is not only suitable for green house air circulation, but also for bathroom ventilation, stove exhaust, kitchen cooking exhaust, etc.
- All-In-One Combo: This inline fan combo enables your ventilation system set up in a grow tent, which is ideal for cooling down heat from lighting fixtures and controlling hot and humid conditions
- Powerful Inline Fan: Made of galvanized steel, the 6-inch inline fan runs at a speed of 2550 RPM and produces an air flow of 390 CFM, with a noise level of just 37dB the maximum
- Premium Carbon Filter: Interior and exterior mesh construction provides 53% open area for free air flow; It is filled with 1050+ RC 48 Virgin Australian activated charcoal captures air contaminants effectively
- Multi-Layer Air Ducting: It comes with 3-layer construction--inner and outer layers are made of heavy-duty aluminum foil that is fire-retardant and its middle layer adopts PET thermoplastic
- 2 Rust-free Clamps: The kit includes a pair of clamps that are made of stainless steel, which are used for securing the connection between ducting and inline fan to keep the connected components in place
- Designed to eliminate odors and chemicals for grow tents and hydroponics room.
- Features premium-grade Australian charcoal with higher absorption and longer life rating.
- Contains heavy-duty aluminum flanges, galvanized steel meshing, two hanging straps, and two clothed pre-filters.
- Enables maximum airflow passthrough for both intake and exhaust configurations.
- Duct Opening: 8” | Length: 20" | Airflow Rating: 770 CFM | Carbon: Australian RC412 at 1200+ IAV | Thickness: 38mm
Use air conditioning units
Air conditioning units do not come cheap, but if you live in places that experience hot temperatures, they come in handy in providing ample circulation of cool air in the grow tent.
Adjust the positioning of the lights
The first thing you should look at if your cannabis plants start exhibiting heat stress signs is the lights’ position. If they are too close to the plants and the leaves are curling at the tips or changing color, readjust the lights’ height. Maintain a larger distance between the lights and the canopies of the plants.
If you change the distance with no positive results, you should consider replacing the light with a different type. The best lighting systems for cannabis plats are LED grow lights because they are easier to control, cheaper, and cannabis plant-friendly.
Read next: Potassium Deficiency In Cannabis
Fit in an exhaust system
An exhaust system provides the grow room with cool and fresh air by sucking out hot, old, and stale air. It works like a reverse fan and, if fitted with a carbon filter, prevents cannabis scents from spilling over to neighboring areas.
- Perfect Combination: Three-part system includes every part you need to get set up; It is primarily used in various air circulation and ventilation projects to move and transport air
- Energy-Efficient Ventilation: The inline duct fan helps solve ventilation problems; This fan is durable and runs smoothly and quietly; Variable speed controller facilitates fan speed adjustment
- Excellent Odor Control: The porous activated carbon with 1050+ RC 48 Australia Virgin Charcoal helps eliminate some of the most undesirable, pungent smells and particulates for indoor grow tents
- Perfect Connector: The VIVOSUN ducts are made of high-quality aluminum; Features a double layer of protection with PET thermoplastic; Comes with two heavy-duty stainless clamps
- Cost Effectiveness: This combination is not only suitable for green house air circulation, but also for bathroom ventilation, stove exhaust, kitchen cooking exhaust, etc.
- LED 300W Grow Light + 24"x24"x48" Dark Room + 4" Filter Exhaust Kit Hydroponics Indoor Growing System
- LED 300W grow light: Featuring a user friendly "Full Spectrum" design, you can easily grow your crops in any growth cycle required like germination, veg, flower
- 4" Ventilation Kit: Effective Odor Control: Eliminate some of the most undesirable odors, pungent smell and particulates from indoor grow tent, hydroponics grow room
- Durable: Heavy duty 600D lightproof oxford cloth and diameter 16MM white paint coated metal rods and Large heavy duty Zippers
- Widely Used: Perfect for your crops, herbs, flowers, fruits and vegetables to thrive in different seasons
- LED 800W Grow Light + 4" Fan Filter Ventilation Kit + 24"x24"x48" Grow Tent w/ free shipping w/ discreet package
- Featuring a user friendly "Full Spectrum" design, you can easily grow your plants in any growth cycle required like germination, seedling, veg, flower
- 4" Ventilation Kit: Effective Odor Control: Eliminate some of the most undesirable odors, pungent smell and particulates from indoor grow tent, hydroponics grow room
- Heavy duty 600D lightproof oxford cloth and diameter 16MM white paint coated metal rods and Large heavy duty Zippers
- Widely Used: Perfect for your plants, herbs, flowers, fruits and vegetables to thrive in different seasons
- 3 Inch Bathroom Fan moves air at a rate of 76 CFM, perfect for your bathroom and utility rooms.
- Lightweight and durable. Radon fan long life ball bearing motor (up to 50,000 hours).
- Hon&Guan 3 inch exhaust fan sound at high speed operation is quiet.
- Duct booster fan 2 connections ways for low speed or high speed.default setting is high speed
- 3 inch exhaust fan Easy to install, disassemble and clean when needed.
- MULTI-ROOM GROW TENTS: this tent features one 24"X24"X53" large tent area room equals to a middle and large plant growing tent for vegetation and flowering. This 4’x4’ grow tent space is perfect for 1-2 plants growing. Meanwhile 2-tier 12"X24"X53" small tent is the perfect nursery area for propagation.
- QUALITY: Durable 600D oxford maylar outside and high-reflective waterproof diamond Mylar inside(enhance the reflective effect),Large heavy duty Zippers & Double Stitching and also 2 Mylar around the zippers for protection against light leaks. Rectangle vents with mesh for better ventilation and multiple vents for fan and filter output, Easy entry and access.
- ADVANTAGE: allowing gardeners to manage plants in different stages of development while remaining compact for small spaces or areas with little height. You could grow seedlings at the 2-tier small tent, and transfer them to the larger tent after they grow taller.
- COMBINATION SUGGESTION: 400W grow lights, LED 300W/600W/ 800W grow lights in the main space and small watt t5 light in the seedling room. 4" ventilation kit is enough.
- ATTENTION: This is a great hydroponics growing tent kit for all kind of growth need. You could grow mushroom, vegetable or flower. When you are using this tent, please adjust the inside flap around the zipper to avoid zipper getting stuck.
Treat damaged plants with supplements.
Some cannabis growers treat heat stress symptoms by using supplements. Even though supplements work in the long-term, they work best only if you use other techniques to cool down the grow space. Some of the best supplements to use for managing heat stress include kelp extracts and seaweed.
Managing Outdoors Heat Stress
Controlling outdoor cannabis is more challenging than doing the same for indoor crops. Crops growing outdoors have to contend with natural calamities such as pest infections threatening the growth and future yields. Even though natural sunlight is good for cannabis plants, too much causes heat stress.
Controlling outdoor heat stress is also challenging, as you have to deal with monsoons and heatwaves. The conditions are especially tougher for growers closer to the equator and warm places. The following tips help in managing outdoor heat stress.
Time your plants watering sessions
Water the cannabis plants when the temperatures are less intense, especially if there is a heatwave. In this case, either watering in the morning or evening is the best option. Watering the plants in the middle of the day will form droplets that may magnify sunlight allowing plant tissue to increase heat.
Read next: How Over Watering Affects Cannabis Plants
Use portable pots
Instead of planting your cannabis into the ground, you can plant them in portable pots that provide you with the option to transfer them to sheltered spots when the sun is too intense.
Build a temporary shelter
Build a temporary shelter out of tarpaulin or cloth to protect the crops from intense heat when it gets too hot. Remove the shelter when the intensity subsides to allow photosynthesis.
Use supplements
Like indoor plants, outdoor crops can also benefit from using supplements to treat heat stress damage: kelp extract and seaweed help increase resilience and provide the crops with extra protection.
- Get your garden going with FoxFarm Grow Big, our liquid concentrate fertilizer that supports lush vegetative growth.
- FoxFarm Big Bloom Liquid Plant Food is formulated for use on all plants and can be used every time you water. OMRI Listed and Registered CDFA Organic Input Material.
- FoxFarm Tiger Bloom is a phosphorus fertilizer that contains nitrogen to support vigorous growth. FoxFarm Tiger Bloom is designed to encourage abundant fruit, flower and multiple bud development.
- FoxFarm Big Bloom, FoxFarm Grow Big, and FoxFarm Tiger Bloom, together at last. Designed to work together to support vigorous growth, multiple bud development and abundant fruit.
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- This starter pack is intended to get you off the ground with your garden. It contains four of our tried-and-true fertilizer products that successful growers, on all scales, have come to depend on.
- Made from the highest quality ingredients, specifically formulated to save you time and money. For use in soil, coco and all hydroponic mediums.
- It’s essential to provide the right nutrients at the right stages of growth. Growth Science will walk you through those steps with this, cost-effective starter pack.
- Each pack contains 5 bottles. 1 pint of Base A, 2 pints of Base B, 1 pint of Solid start, and 1 pint of rock solid
- Base A and B form the foundation of the Growth Science system. Together they provide your plants with essential macro and micro nutrients essential for growth.
- Lush, sturdy growth from 3-part nutrients designed specifically for high value
- 3 Part solution in 1 package: You get advanced nutrients bloom, micro and grow in 1 liter size each
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- A 3-pack of favorite liquid fertilizers from FoxFarm
- Get the right juice for the right use
- Start with Grow Big Hydro for abundant green growth
- Switch to Tiger Bloom at the first sign of bud set or flowering
- Use Big Bloom throughout all growing cycles to heal root systems and increase nutrient cycling
Grow heat-resistant strains
You can also reduce the risk of cannabis heat stress by growing strains that come with high-temperature resilience.
Wrapping it up
Heat is a necessity for healthy plant development. However, if the plants get too much heat, it leads to heat stress, which becomes a problem. However, if you follow the above tips, you can manage heat stress easily and in time to save your cannabis plants.
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