Tip #1: Watch for the Signs of Heat Damage
If Subalpine fir overheats, there may be warning signs before it begins to die off. First, the leaves may begin to brown, then branches could begin to fall off. This is because the branches themselves are dying as the tree pulls moisture back towards its center of mass. Make sure to keep temperatures lower, and water your Subalpine fir more frequently if they are exposed to heat.
Tip #2: Don’t Let Subalpine fir Get Too Cold
While Subalpine fir does prefer cooler environments, letting the temperatures drop too fast can begin to cause freeze damage. If your growing area dips fast below 5℉(-15℃), the water in your Subalpine fir can begin to freeze. This causes the cell walls to burst and the bark to crack. This could slow growth significantly, and if temperatures don’t increase, may begin to cause parts of Subalpine fir to die.
Tip #3: Use Shade and Ventilation to Help Keep Temperatures at the Right Level
If you find that Subalpine fir is starting to overheat, you can use a combination of shade and ventilation to help bring temperatures back down. If you don’t have access to an air conditioning unit or fans, shade and ventilation are a good cost effective way to bring temperatures back into the optimal range. Once temperatures are corrected, though, make sure to let your plants get sunlight. Subalpine fir needs a lot of sun to grow properly, so while shade could work in the short term for temperature correction, Subalpine fir should not be left in the shade for too long.