MEDITERRANEAN SURVIVABILTY INDEX ZONE 2A: The Queen Palm
This is a pretty narrow zone with only a degree or two separating the two palms at either end. I am going to list only the palms that survive around 20F/-6.66C. I will list them in alphabetical order only because I really cannot separate them in any other way- these palms may not act the same in one microclimate as another, and tall palms seem much hardier than short ones... so that will affect people's experiences. For the most part, the palms listed here could all be interchangable in terms of hardiness order.
The 20F/-6.66C group:
Acoelorrhaphe wrightii is probably hardy to about 20F/-6.66C... but if exposed to lower temps, it can often grow back, being a suckering palm. It is one of the more adaptable palms being extremely happy in a high humidity situation, as well as a desert one.
Arenga engleri: probably as cold tolerant, if not more so... but about the same. Whether or not these two are really less cold tolerant than P. canariensis is debatable.
Brahea aculeata: not nearly as adaptable since it hates humidity, but it is one of the most drought tolerant palms there are. Hardy to around 20F/-6.66C
Brahea edulis: about the same, perhaps a tad less hardy.
Brahea calcarea: maybe even a bit hardier (some say below 20F/-6.66C)
Butia capitata X Syagrus romanzoffiana: lots of debate on this one's cold hardiness... may have to do with how much Butia is in each palm, so some could be more cold hardy than 20F/-6.66C.
Dypsis decipiens: adult palms are probably cold tolerant to around 20F/-6.66F, but seedlings most certainly are not (damaged from cold at 25F/-3.88C).
Livistona australis: probably cold tolerant to about the same temps
Livistona chinensis: ditto- some claim this is the most cold tolerant Livistona, but in Mediterranean climate so many seem equal
Livistona decora: maybe even a bit more cold tolerant than L. australis
Phoenix reclinata: probably close to these other palms, but more adaptable in terms of growing back if froze badly.
Sabal bermudana, causarium, palmetto, 'Riverside' are probably all about the same, with S. palmetto perhaps being the wimpiest of the four.
Trachycarpus takil: though listed as a 20F/-6.66C palm, it could actually be a bit more cold hardy... just not enough experience with it yet.
Trithrinax campestris: about the same.. maybe a degree or two less hardy.
Washingtonia robusta and Syagrus romanzoffiana are in this same zone, but probably a tad less hardy than these others by about half a degree or so. Some see burn on one species and not another in certain situations, and vice versa in other situations. Palmbob 15:16, 20 July 2007 (PDT)