Frost tolerance of Sonoran Native Plants

Randia echinocarpa, a very cool Tropical Deciduous Forest and Thornscrub plant from Sonora, has proven itself hardy to the lower twenties to high teens. Sometimes they defoliate and sometimes they don't. Information is confusing at this point. At any rate the only plants of Randia I had freeze on me were 1 inch tall seedlings that were in open sky (those with just a little shadescreen over them did fine). Seedlings that were bigger than a few inches survived low temps.

Sabal uresana, the Mexican blue palmetto, had fared well as specimen plants and is known for being somewhat hardy. However I have many seedlings that have also fared well in these stupid winters we have here (I hate winter if you all haven't guessed by now!). This is impressive because even seedlings of some totally hardy plants I have had freeze. Monocots that have sheathing tendencies are great seedlings. They are always so tough!

There are a lot of neat Sonoran oaks (Quercus spp.). I am growing seedlings of Q. albosincta, Q. viminia, Q. cytophylla, Q. mcvaughii, and all have been left uncovered almost all winter (as seedlings) and not any frost damage. No big surprise to me. They ARE oaks. But some people I know had doubts. Always have faith in the oaks. They are trustworthy.

For cactus people: Ferocactus potsii and F. alamosana have proven themselves good at least to mid teens F. Agave Bovicornuta also does not freeze in Tucson. I always leave mine outside. It is huge now too (about 2 1/2 feet diameter). Most of the Sonoran Agaves have proven themselves hardy and I think that a surprise.

How about you all? What are your hardiness reports?

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