Are you using the mist to lower the temperature or raise the humidity? In the summer I move out of the greenhouse into a plastic covered carport open at both ends with a canopy of trees providing mostly shade. I can lower the temperature in the greenhouse about 10 degrees with mist which raises the humidity from 25% to 40%. The result is too dry and too hot. In the carport the temperture is better and I may have to tent the softer cuttings to prevent wilting. Al

I once had a lath house in Phoenix and I hooked my mist system up to a thermostat. It came on for several seconds or a few minutes whenever the temperature hit 85°F and it was quite successful. I saw it as providing just about the right amount of humidity and temperature control. However, note hat I had very good circulation. Some professionals had greenhouses in Phoenix but I completely failed in getting enough circulation and cooling to keep the temperature of a greenhouse down in Phoenix.

Summer time high heat causes plants to stress out in the GH resulting in insect invasions; one must be on constant guard.

Heat and lack of air circulation is also the cause of propagation failure. Do you use at least a 50% shade cloth in the summer; have circulating fans/exhaust system? One inexpensive system I've seen for containing mist is to place clear plastic shower curtains, just as one might see in the bathroom, around the mist bench to contain moisture, yet allow some air circulation without blowing the cuttings away. Unless you have a water wall in your GH and shade cloth you may have to abandon propagation there during the brutal summer months especially if your GH has western exposure.

Another system may be an inexpensive propagation set up under shade trees outside where temperatures are more moderate, just as the person above suggested.

Do you keep a notebook recording details, successes and failures? Do you have a set up for min/max temperatures in your GH?

Thanks to everyone for the advice and information. I will try to implement various things from this thread next spring.

My greenhouse has a northeastern exposure, which is pretty ideal for here. However the sun gets at a very high angle in mid spring and it still gets more sun than I would want during the highest heat period. I will try the shade cloth then.

I was thinking of trying to find a humidistat or themostat that could interface with my misting system. If anyone has experience with a humidistat/mister, let me know. I will also try the curtain idea.

I was actually using A/C to cool this past summer. I think that made the situation worse, as it tends to dry out the air. I am thinking of trying a small "swamp cooler" type unit (like the water wall on a smaller scale), if I can get one hooked up.

Thanks again!
John