It can be easy to miss the signs of heat stress or mistake them for something else. Overfeeding, for instance, can also cause leaves to curl, although typically this condition won’t come with that same burned-out look. It’s important for a grower to carefully differentiate when examining a distressed plant. While overheating can severely damage a cannabis grow, there are a number of relatively simple measures that a technologically equipped grower can take to both prevent and remediate heat stress. An environmental management system should be implemented to track temperature, as well as humidity, nutrients, and other key factors.
Equipped with such a system, a grower who cannot be on-site 24/7 still can observe temperatures and even make adjustments with a smartphone app. Low humidity can worsen the symptoms of heat stress, so keep an eye on this measure as well. Here, again, a system of sensors and monitors, along with remote management tools, can help a grower contain the issue relatively easily. The next step is to consider circulation and make sure the heat is distributed evenly throughout the room. A small fan blowing over the tops of plants can help keep hot spots from forming under grow lights. Experts recommend using a carbon scrubber to avoid pumping undesirable aromas outside. How close are your lights to the tops of your plants? Sometimes a small adjustment is all that is needed to bring the temperature down.
Some trial and error may be required, but it’s worth the effort to find a position that gives the plants maximum light without the risk of overheating. In addition to watching for signs of heat stress, a simple manual check can indicate whether lights are positioned too closely to the plants. Hold your hand under the light at plant height for a minute. If the heat is too warm for comfort, you probably need to increase the distance. Likewise, it can be helpful to position plants in a way that allows free flow of air around the base of the plants. While heat stress shows up in the leaves, it can start in the roots. Keeping the roots cool is an important part of overall environmental management. Heat stress can damage crops if left unchecked, but it can be easily prevented. Sensors and monitors, paired with remote management, enable the grower to keep heat at appropriate levels without always having to be on-site. Published : Sep 27, 2017 Categories : Cannabis cultivation. While heat is a necessary component of healthy cannabis plant growth, overheating can cause adverse reactions that will detract from proper development and ultimately, the quality of your yield. Find out how to recognise and prevent heat stress from damaging your crop. All plants require heat to grow and develop properly. Below, we attempt to find a balance below the upper threshold of how much heat your plants can handle. When it becomes too cold, plants cannot grow or even germinate from their seeds. A stable temperature will help young plants develop root systems faster. By keeping track of night temperatures, you can make sure that above-ground growth, that means leaves and stems, will also be abundant. Essentially, when your marijuana plants get too cold, their growth is stunted, slowed down, or in some cases, halted completely. And while heat prevents this from occurring, there is also such a thing as too much heat for your cannabis plants. There are several signs that indicate your plants are suffering from heat stress. First, the ends of leaves will start to curl up - a phenomenon easily and often confused with overfeeding. The main difference between heat stress and overfeeding is that with the former, the entire sides of the leaf will curl up, not just the ends. Also unlike overfeeding, leaf ends will not become “burned” by nutrients. Therefore, be on the lookout for curling leaves unaccompanied by other overfeeding symptoms.
If there is very low humidity in your grow room, or your local climate is very arid, cannabis plants are more prone to developing “cupped” leaves from the heat. Even though the heat might not appear to be very harsh, when combined with low-humidity, the two can wreak havoc on your plants. Especially when you want to keep your plants in low humidity to combat top rot, keep a very close eye on your leaves’ edges. Flowering plants are even more susceptible to heat stress. If too many leaves become damaged by overheating, the cannabis plant will respond by growing buds with lower potential. This abnormal formation of buds can manifest in what is known as “foxtailing,” which usually occurs in buds closest to your grow light. The buds may also display new growth at a much higher rate toward the top of the bud than on the bottom. These newly formed pistils are usually white and give the appearance that the bud is not ready for harvest. If this happens, it is a telltale sign of overheated cannabis plants.
Upon deciding when to harvest your plants, pay attention to the lower end of the buds as this will give you the best indication of their actual maturity. There are several ways to help your plants withstand higher temperatures or recover from past heat damage. The availability of solutions, however mostly depends on the environment that you are growing in. The most universal solution is to make sure you have adequate temperature monitors in place.