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.
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.
- Remotely connect to our WiFi app to access advance programs, view climate data, and set automation.
- 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
- Powerful Airflow: This VIVOSUN powerful blower with a fan speed of 2500 RPM can create an airflow of 195 CFM; It works efficiently in ventilating grow tents, transferring heat or cool rooms, circulating fresh air, as well as controlling proper humidity, temperature, and air quality for your grow area
- Quiet Operation: Fitted with a flow deflector that concentrates the fan stream and cuts turbulent kinetic energy to reduce sound output to just 30 dB, which does not have any harm to your health and will not disturb your work
- Safety Protection: The motor is ETL listed and features an automatic reset function to prevent overheating or other safety issues; The electrical junction box is made from flame-retardant components for fireproofing
- Simple Hookup: The flanges on both the intake and exhaust ends are simple to assemble with the vent hose by locking tabs; A cord of 5.9-feet long for hassle-free setup; The housing, even the impeller and blades, are easy to detach for cleaning and maintenance
- Wide Applications: It can improve airflow to reduce humidity, block odors, and lower temperatures in grow rooms, basements, or kitchens
- High Efficiency & Energy Efficient Fans: Remove heat from the system to solve air delivery problems without the additional hassle or expense of major system rework. Ideal for industrial, home and garden ventilation applications for air cleaning and temperature control
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- Low noise: Durable fan blades rotate smoothly and powerfully, helping to collect airflow and reduce noise output; composite fan blades and center hub, reducing noise and vibration without affecting daily.
- Adjustable speed: A stepless speed controller on the power cord allows the fan to run at different speeds as needed; with this speed switch, you can adjust it to the desired airflow level.
- Durable Fan: Made of high quality cold rolled steel. The surface is treated with a plastic sealant for high corrosion resistance. The tight and precise construction reduces wear and tear, thus extending the life of the components
- Variable speed controller: Enable you to adjust the speed and airflow of the fan. Note: Please turn the fan off immediately if the blades get stuck by other objects and turn on after clean.
- Efficient and high safety: Feature a diameter of 4 inches, speed of 3200 RPM and 90 CFM air flow. With insulating coating, high safety factor. Portable, lightweight and easy to install.
- Durable: Superior balanced centrifugal impeller for long service life. The motor features a permanently lubricated bearing that operates quietly and requires no maintenance. Note: Not enclosed motor, not used in high humidity environments.
- Wide application: Used as intake fan to bring fresh air into grow rooms, help to boost airflow in HVAC units to remove exhausts and odors from workshops and ventilate basements & attics, etc.
- Specification: Voltage: 110-120V; Wattage: 15W; Power Cord: 4.9FT. Max operating temp of motor is 130℃ / 266℉; Max ambient temp is 60℃ / 140℉.
- Universal Applications: Take a deep breath and relax. Our inline duct fan is specially designed as an exhaust for heat, humidity, and smoke, improving airflow in air planting tents, hydroponic planting rooms, electronic equipment rooms, kitchens, basements, etc. Get ready to go with the flow.
- Blow Your Worries Away: Our inline fan provides a sufficient airflow of 402 cfm, enough to handle wide areas of ventilation and dehumidification, maintaining clean and fresh air circulation in dry environments all the time. Take control of any environment confidentially.
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- Take It Easy: VEVOR's inline air duct fan adopts a smart controller. You will freely switch the ON/OFF/TIMER/AUTO modes (High Temperature; Low Temperature; High Humidity; Low Humidity). Pressing the UP and DOWN buttons simultaneously will turn the AUTO MODE off. The auto alarm function is also included. The controller automatically starts or stops according to the temperature and humidity. Note: The controller does not adjust the speed automatically. The speed can only be adjusted artificially.
- Everything You Need: To save time and costs, we provide a 6-inch inline fan with stainless steel clamps, and non-vibration rubber mats and straps, allowing you to effortlessly complete installation. Additionally, you are not restricted in how you install the high-quality duct fan. Choose between hanging it or mounting it on the wall.
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.
- LOW NOISE SILENCER: designed for reducing noise from fans and carbon filter systems, can decrease the noise by up to 50%.
- 6" DUCTING LIGHTPROOF: Thick layer of Black PVC on Hon&Guan ducting prevents light leaks. Works with exhaust and intake fans, carbon filters and hooded lights which are 6" in diameter
- 3-LAYER TOUGH: Keep your ventilation system free of rips and pin holes. Under the Black PVC layer our ducting is built with 2 layers of Aluminum Foil With a layer of PET and Steel Wire Helix to preserve the shape,keep your ventilation system free of rips and pin holes
- FLEXIBLE AND EASY TO USE: Hon&Guan 6 Inch Duct is super flexible and easy to install, it will slide right on your Duct Fan, Vent Exhaust, Carbon Filter or Light Reflector.This Ventilation Duct is 6 Inches in diameter and comes in one 16 Feet Long Piece, which can be cut into as many pieces as you need using a wire cutter and a paper knife
- VARIETY OF APPLICATIONS: Hon&Guan Ducting Is suitable for HVAC system. It will move and deliver air in Kitchens (cooking exhaust), Green Houses and Grow Rooms (Air Circulation, Intake, Exhaust and Light Fixture Cooling), Bathrooms (Smell and Moisture Exhaust), Dryer Rooms, Grow Tents and other applications etc.
- Non-insulated Ducting: 6" diameter x 25' feet long air duct, made of thick and durable aluminum, fire-resistance coating foil vent ducting with 2 metal clamps, the 6 inch flexible clamps fits fans and vents, simple to keep clean, great for using a diversion vent at temperature range from 0 to 185+ F.
- 6x25 Spiral Ducting: Wide variety of applications in ductwork system, heat filters, medical rooms, air conditioner, allergy room m, bathroom, greenhouse, tent grow room, air tight system and stove vent, circulating the atmosphere, air-conditioning the flow, removing heat from an enclosure, distributes CO2, increases temperature & humidity levels and etc.durable and resistant to leaks, tears, and cuts.durable and resistant to leaks, tears, and cuts.durable and resistant to leaks, tears, and cuts.
- Tight & Flexible: Ductwork heavy duty helically shaped and internally crimped corrosion resistant wire helix interlocking steel strips to form an air tight and leak proof system, flexible to expand and stay strong as a clothes dryer transition duct, ventilation tent air blower, flange system cleaner, etc.
- Easy to Install: To cut and poke a hole in the duct with a screwdriver and tear around it with finger. Then use side cutters to clip the support wire.durable and resistant to leaks, tears, and cuts.
- CUSTOMER CARE: We offer premium products for you while exceeding highest industry standards and offer thoughtful and considerate customer care.
- 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.
- Mini construction fan: Size: 4 inches; Voltage: 120V; Current: 0.45A; Frequency: 60Hz; Power: 28W; Air velocity: 195 CFM; Speed: 2500 RPM. Low noise design reduce sound output to just 30db
- Ducting: Size: 4 inch; length: 8 feet; material: PVC thermoplastic (prevents light leaks); inner material: aluminum foil. Temperature range: -22°F~212°F(-30℃～100℃). High temperature and corrosion resistant, long lasting. A pair of duct clamps included
- Air carbon filter: Air flow: 200 CFM; dimension: 4 inch flange ducting x 12 inch length. 1050 + IAV Australian RC412 activated carbon. 50mm carbon layer of thickness for higher absorption and performance
- Multi-function: This ventilation combo removes heat and eliminate the undesirable ill-smelling odors in the grow tent to solves air delivery problems without major system rework or expense
- Package includes: 1 x 4 inch 195 CFM inline duct ventilation fan; 1 x 4 inch air carbon filter; 1 x 4 inch 8 feet four-layer design ducting with 2 clamps
- Ultra-quiet UL-certified USB fans designed to cool various electronics and components.
- Features a multi-speed controller to set the fan’s speed to optimal noise and airflow levels.
- Dual-ball bearings have a lifespan of 67,000 hours and allows the fans to be laid flat or stand upright.
- USB plug can power the fan through USB ports found behind popular AV electronics and game consoles.
- Dimensions: 4.7 x 4.7 x 1 in. per fan | Total Airflow: 104 CFM | Total Noise: 19 dBA | Bearings: Dual Ball
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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- The FloraSeries is a hydroponic-based nutrient fertilizer system that helps fulfill your plants’ nutrient needs at every stage of growth
- Nutrients included are FloraMicro, FloraBloom, and FloraGro
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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.
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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