Do you know about Wollemia? Discovered in 1994 in a remote part of a national park in NSW Australia, and kept a secret for its protection, it created a sensation in the botany world.
In 2020 the one area where it occurs was threatened by wildfires and a special division of firefighters was deployed to protect it.
I first saw it in the Royal Botanical Gardens, Sydney in 2000, and it was protected by a very stout steel cage. The species has been tissue-cultured, and is now available (for a price).
This one in SF Botanical Garden must be one of the bigger ones in North America. At about 10 years old it is over 20 feet (6 m.)
I have no idea how frost-tolerant they are here, but they have survived below 15 F. (-10 C.) elsewhere.