How low can a mature one take and have no more than about 1/4 branch die back?
I've heard they can take 13F and I've also heard one report of 0F (but that maybe a false rumor).
The Juanita is a seedling cultivar of Satsuma; so it should tolerate short periods of 25 F, or lower if covered.
The important thing to remember about cold tolerance... not only for citrus, but for all plants is that the empirical number, e.g. 25F is not so important as the other environmental factors. Dew point (a measure of air humidity) too low can mean the plant will stand less cold; if the ground is moist, the plant will tolerate lower temperatures; if you have good air drainage it helps; if you plant in a low area the cold will "settle" there (as they say in golf, air, water, and golf balls all flow in the same direction); the duration of the low point is equally important; the longer the low temp, the less the plant can withstand it. Exposed -vs- protected; against a warm wall for example means the microclimate of the plant may be warmer than the ambient temperature; if there is vegetation under the tree that raises the effective orchard floor to the top of the vegetation. Sometimes even a very small attempt to protect the plant can make a big difference; in Northern California, on the coldes nights I used to just throw a sheet over the tree and hang a 60W lightbulb in the branches.
Thank you for the good info.