Cannabis Heat Stress

Cannabis Heat Stress cultivation may seem fairly obvious, and avoiding it may seem simple, but your cannabis plants can experience a number of problems – such as discolouration or burning – as a direct result of heat stress. This can have serious consequences for the health of your plants and the quality and quantity of your harvest. As you can probably imagine, this is not a pleasant experience, so before you start growing, it is important to understand the causes of heat stress in marihuana, as well as how to prevent and treat it if you find that your plants need rejuvenation.

What Is Heat Stress?

Cannabis plants, like other common plants, can only withstand a certain amount of heat/light, and excess heat can lead to heat stress and ultimately heat burn. While heat stress is bad for your plants, too little heat can also have a serious impact on your performance, so it’s important to maintain a healthy balance in your growing environment. Your marihuana plants require the right amount of heat from start to finish; indoor plants will thrive in temperatures between 70-75˚F during light periods and 50-60˚F during dark periods.

Why Is Overheating Dangerous?

Heat stress in cannabis is a common problem that can have drastic effects, potentially ruining your plants completely and/or significantly reducing the quality of your harvest. If your growing space or plants are too warm, it can directly affect the appearance and health of your cannabis. The cannabinoids and terpene compounds in cannabis are volatile and polymerise quickly, so it is important to maintain a cool climate to preserve the full profile of cannabinoids and terpenes.

In addition, there is a natural degradation process towards the end of the marihuana growth cycle: THC-A to THC. This can be seen visibly when the trichomes change colour from translucent to milky or amber during the harvest window. However, the effects of heat stress can accelerate this process, making the plants appear ripe and ready to harvest long before they actually are.

For this reason, it is important to make sure you know how to recognise heat stress in cannabis.

Symptoms Of Overheating

The symptoms of overheating at the flowering stage are different from those at the vegetative stage, and the risks associated with heat stress also vary according to the growth stage. It is therefore crucial to understand what these problems are, why they happen and how to prevent them.

An important sign of overheating is when the tips of the fan leaves start to dry out and curl upwards (also known as a ‘taco’ because the shape of the leaves resembles a taco). If this happens mainly in the upper part of the plant, it is usually a sign that, in addition to heat stress, the plants are also experiencing light stress (as both often occur simultaneously).

Here are some other key symptoms to help you identify cannabis heat stress:

Leaves begin to look dry and withered.
Whitening of the leaves in the upper part of the plant.
Leaves with large brown spots that are arranged in irregular shapes.
Yellow discoloured spots become visible (but without physical damage).
Fox-tail formation – new growth on top of mature flowers.
Leaves looking burnt at the tips.

It is important to correctly identify marihuana heat stress, as there are other problems that can cause similar symptoms (namely, nutrient excess/deficiency and/or light stress).