SUMMER'S TOO HOT
I have some plants in 15 gallon white containers on my roof deck. It gets great sun and fresh air, but it can get too hot. On sunny days, it can reach 38º. What should I do to protect the plants from too much heat?
As the temperature heats up the plant's metabolism and rate of photosynthesis increases up to a point. At about 32º the photosynthesis process shuts down as the plant goes into stress mode and uses its energy to transpire water to cool itself. On days when a substantial portion of the day is above this temperature the plant photosynthesizes for just a portion of the lit period.
There are two ways that you can help the plants during this stress period. One method is to keep the plant roots chilled to 20-21º. The cool roots help to cool the canopy.
Another method is to use micro-misters that emit very small droplets of water that immediately evaporate and cool the surrounding air. This can cool the air up to 10º. One method uses an evaporative cooling device with an oscillating fan. A tube carries water from a reservoir and drops it onto the spinning blades that smash it into tiny bits. A single fan can cool about 18 sq m. Another way of cooling with micro-mist is by using micro-misters that emit the small droplets. A pump that creates water pressure in the misters is part of the set-up. You may be familiar with these misters as they are sometimes used at public gatherings during the heat of the summer.
The mist evaporates before it has a chance to touch the leaves so there is no problem with water damage.
Growers who have used light deprivation for early flowering sometimes produce buds that are loose, rather than tight, as a result of summer heat. Using a mist system controlled by a thermostat installed at the top of the plant canopy solves the problem.
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Soft Secrets
