As you can see in this photo of Lucky 13’s Seed Co.’s Peanut Butter OG, cannabis is perfectly capable of thriving in intense summer heat. This photo was taken during a week when temperatures were consistently above 40c/105f. However, in order to keep your plants from suffering heat stress, you’ll need to take some proper precautions. In continuation from Part 1, let’s dive a bit deeper into some tactics for reducing heat stress in your outdoor cannabis garden when the mercury hits the boiling point.
Lower fertilizer concentrations: If you’re feeding liquid salt based nutrients in hot weather, you must lower the concentration of your feedings. The plant will be transpiring at an accelerated rate while the actual nutrient demand is reduced (cannabis will slow it’s growth in hot weather). Most liquid nutrients are taken up via osmotic pressure, so this means that while the plant is drinking heavily in hot weather, it is also being force fed more fertilizer than it can handle. In this scenario the risk of nutrient burn is high.
Adjust nutrient ratios: As cannabis’ demand for water increases in hot weather, so does it’s need for potash/potassium. In order to ensure your plant maintains healthy growth during hot spells, it becomes essential to provide enough potash to replace what is being flushed out from the root zone by heavy watering. While many bloom nutrients contain plenty of this essential nutrient, they also come with a hefty dose of phosphorus which is not needed at this stage. Soluble kelp is the perfect solution here. It won’t raise the EC of your water much (preventing the nutrient burn I just mentioned in the previous tip) and it contains plenty of potassium. A small dose (around 0.3 EC) with each and every watering in hot weather will go a long ways in helping you avoid potassium deficiency. Think of it as Gatorade for weed.
Supplement with silica: Silica is not considered an essential nutrient by most nutrient manufacturers, and thus is absent from the vast majority of fertilizer programs. However, silica can vastly increase the heat tolerance of cannabis as well as strengthen stems and stalks. It also increases pest and disease resistance quite substantially. Add silica to your soil by top dressing with diatomaceous earth, or invest in a liquid potassium silicate product such as Grotek’s Pro-Silicate, General Hydroponic’s Armor Si, or Green Planet’s Plant Guard.
...concluded in Part 3 coming tomorrow.
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