Q.How long does it take to kill a sago plant at 23 degrees?
I am looking at the cold tolerance for sago plants. On your web site, it says the can withstand 15 deg. for brief periods, but they will be killed at 23 deg. I don’t understand that disparity. Do you mean 23 deg. for a long period, say 5-6 hours, or what?
I agree that is confusing and should be written differently, but it is not the only article where this disparity exists. There is no definite answer to your question of how to walk on the edge. There are too many variables. Is your plant flush with perfect high nutrient density and moisture content, or is it under physiological stress already? That's why articles seem vague, because plant health and resistance and growing conditions are never the same and they behave differently. There can only be general guidelines, not exact numbers.
The bottom line is that sago palms are not suitable for planting outdoors in your climate, which is 8a in the USDA Plant Hardiness Zones. Sago palms are suited to zones 9 - 10.