I come from the southwestern Arizona desert where temperatures can reach up to 115 to 120*F in the summer.
I’ve been growing marijuana outdoors for two years, and, when I first started, I would keep the plants in full sunlight for the entire day. This ended up killing the plants by June. To remedy this situation, I’ve just been keeping them shaded from the East so that they only get direct sunlight from 2 to 7 PM. Is there any other feasible way to keep my marijuana plants from being affected by the awful, dehydrating sun?
Hot, dry climates with clear skies don’t have to be stressful for marijuana. The plants in your garden likely died because they did not get enough water or had shallow roots which were fried in the hot upper part of the soil.
If the marijuana plants are watered satisfactorily enough, the water will penetrate straight down into the medium and the roots will follow it down. Deeper soil layers won’t exhibit the same radical temperature changes found in upper layers.
During the summer, it’s particularly important to never let the soil dry out. The roots draw water up that is then transpired by the leaves. If the water source dries up, the leaves will start to lose the water from their cells. They will also lose their turgidity and begin to wilt. As the drying progresses, more and more cells start to die. Even a minor wilt due to water stress damages the marijuana plants. If they are not watered at the first sign of stress, they can die in a matter of hours.
Sometimes the plant’s leaves will droop slightly during the hottest part of the day, even when it’s had enough water. This is a normal reaction that might just be a protective measure used by the plant. When the sun gets too intense for the leaf, it shifts its angle by wilting so that it receives less sunlight.
Marijuana plants grown under partial shade with these same conditions perform well. The soil is unlikely to go through any radical changes in temperature, and the plants get enough light to grow and produce. In some areas, indirect light might provide enough intensity (if there is no cloud cover) to produce decent yields.
Gardeners might be interested in a few commercial products to help with those sunny, hot, and dry climates. Anti-transpirant sprays will mitigate water loss during particularly stressful periods. Directions on these sprays indicate that they’re useful for transplanting and for enduring stressful climatic conditions like hot, dry winds. You can find these products at many nurseries.
Another option is water-holders which are made from starch and polymers. They resemble corn flakes and are relatively lightweight when dry. You mix them into the soil and, when they contact the water, they sort of balloon to hundreds of times their weight in water. A single tablespoon of flakes can hold 6 to 8 ounces of water. When the soil dries, the particles start releasing their moisture. The soil maintains its dampness longer and less water is lost overall.