3 Proven Supplements to Help Cannabis with Heat Stress

by Nebula Haze

High temperatures can make growing cannabis a lot harder, even if you’re growing with heat-resistant strains. Droopiness, nutrient deficiencies, crispy brown leaves, and overall slow growth are common symptoms of heat stress, whether your plants are growing indoors or outdoors!

We already have tutorials on controlling heat indoors, circulation and exhaust, as well as how to help outdoor plants during a heatwave, but can a marijuana supplement boost the plant’s ability to survive and thrive in heat without changing anything else about the environment?

Actually…yes! There are 3 specific supplements that are known to help cannabis plants be more overall resistant to heat stress, drought, and high temperatures. Just water your cannabis plants with these all-natural supplements and it will help get them through those too-hot days.

Help your marijuana plants be more resistant to heat stress, unlike this poor baby!

1.) Seaweed Kelp Extract

There are numerous studies showing that seaweed kelp extract is beneficial for heat-stressed plants when used as a supplement. Seaweed kelp extract (available as a liquid or powder) has been shown to increase yields, growth rates, and heat resistance in plants experiencing environmental stress.

Kelp naturally contains lots of trace elements and minerals that have protective properties for plants. Studies have shown that supplementing with kelp can increase plant yields, growth rates, and heat/drought resistance for many species of plants.

Besides protecting against heat, kelp supplements may also enhance seed germination, increase uptake of plant nutrients, and give more overall resistance to frost and fungal diseases.

2.) Humic Acid Supplements

Humic acids are naturally found in the soil, but adding extra can be beneficial. Plant supplements for humic acid are usually derived from leonardite, a substance that is mined near the surface of lignite deposits (lignite is sedimentary rock that formed over millions of years from compressed peat). It is a waxy, brown substance.

Humic acids have protective abilities and can help cannabis plants deal with water stress and drought. Additionally, there is quite a bit of evidence (mostly with many different types of grass, but also with plants like soybeans and corn), that combining humic acid supplements with seaweed kelp extract actually increases the overall effectiveness of both supplements. They may have a synergistic relationship.

Not only do humic acid supplements help protect the plant against water stress, but they may also enhance the heat-resistance benefits of using sea kelp extract. Here’s an example of a liquid supplement that contains both Humic Acid and Kelp (though it’s much more expensive than getting them separately).

Humic acid comes in soluble powder form

Alternative: Kelp + Humic acid together

Get a product with both kelp and humic acid like this bottle. It’s mixed with water you’ll get less total humic acid and kelp compared to buying everything separately, but very convenient.

3.) Silica Supplements

Silica is not a “required” nutrient and your plant won’t suffer from Silica deficiencies. However, supplementing with extra silica offers additional support to plant cell walls. This helps your plants be more resistant to heat and other types of stress. This not only makes cannabis plants more resistant to heat, but it also helps prevent stems from bending or breaking when buds get big and heavy! Have you ever had your buds fall over from being too heavy? Silica can help!

Botanicare Silica Blast or General Hydroponics ArmorSi are examples of silica supplements made for plants

Whenever possible, try to get a silica supplement from the same manufacturer that makes your base nutrients to help ensure everything works well together. Like if you’re using Botanicare nutrients, get Silica Blast. If you’re using General Hydroponics, get ArmorSi. However, sometimes that’s not possible. In that case, I recommend Silica Blast as it seems to “play well” with most nutrients.

Heat-Resistant Strains

Every strain is different. Some strains of marijuana are easily stressed by heat, while other strains would thrive in the exact same environment!

When it comes to strains that tend to be more resistant to heat stress…

Sativa, Haze, African and Hawaiian strains all tend to be more heat-resistant since they originate from hot climates.
In general, auto-flowering strains to be relatively sensitive to heat since they originated in Siberia, but some strains have been mixed with heat-resistant strains to make them more suitable for warmer climates.
Many Indica plants, which also come from cool climates, can be surprisingly sensitive to the heat.
Plants that grow tall and stretchy with narrow-finger leaves tend to be more resistant to heat
Plants that grow short and squat with big fat leaves tend to struggle more.

If you’re not sure which strain to get, check out some of the suggestions below!

Grow more heat-resistant plants by choosing the right seeds

Example of Heat-Resistant Cannabis Strains

Orange Candy / Naranchup

In addition to doing well in the heat, this strain is overall easy-to-grow and resistant to pests and mold
Has a surprisingly short flowering stage (8-9 weeks) for a Sativa-dominant strain, and doesn’t get too tall
Buds produce psychedelic and cerebral effects that are typically not overwhelming and can be a good choice for improving creativity
Get Orange Candy seeds

The Orange Candy (also called “Naranchup”) strain thrives in the heat. This plant experienced temperatures over 95°F (35°C) yet the plants didn’t seem fazed.

Northern Light (version by Royal Queen Seeds)

There are many versions of Northern Light, and all tend to be hardy strains
However, the version by RQS is particularly resistant to many problems, including heat. In fact, it thrives in heat.
Like all RQS strains, the smell and potency are delightful
Get Northern Light seeds (Royal Queen Seeds version)

These Northern Light buds lived through intense heat and a too-close grow light, yet the resulting buds seemed mostly unaffected

THC Bomb Auto

An auto-flowering plant that’s ready to harvest about 75 days from germination in my experience
I’ve grown it several times, and it always turns out well (though they all grow a little different)
This strain experienced temperatures up to 89 F during the middle of summer, and never skipped a beat
Very potent strain, and good yields
Get THC Bomb Auto seeds

Examples of THC Bomb Auto at harvest (this plant survived multiple heat waves)