I wish I could have gone since I'm very interested in using native plants.

Anytime can theoretically work, but it's definitely more difficult during the dry season. Many natives are very sensitive to transplanting stress, which is greater if you're transplanting them in the summer heat. If you plant any natives in the summer, I recommend planting them at night, so the roots aren't exposed to quite as much heat during the transplanting process. Planting them during the very end of the wet season can also cause problems, because the plants may not have time to get their roots out before the summer drought sets in. I planted a silver bush lupine this past March, and it grew a foot, produced a flower spike, then shriveled up in May and hasn't recovered, despite the fact that I'm now watering it considerably more than before. (It's not actually dead so far, but it looks terrible, and I don't know whether it will survive or not.) My other silver bush lupine, planted in January, is still perfectly healthy - probably because it had more time to get its roots out before the summer. A lot of natives are also prone to die from overwatering, especially in the summer, so I think it's much safer to try to plant natives early in the wet season and let them get their roots out before summer, rather than planning to give them extra water during the summer to keep them alive when they're newly planted.

I would hate to introduce new pests as well, but millions of plants are moved across state lines every year. If you are not in a quarantine zone, I don't see a problem with choosing your favorite plants, spraying them thoroughly and inspecting them visually and replacing as much of the soil as possible in OK (unnecessary with cuttings, obviously). Just try and keep the entire operation as sterile as possible. Additionally, many moving companies may have restrictions on transporting live plant material. I believe the law requires you check with the ag depts of both states before moving.

I have to agree with Bahia, here. There is a reasonable level of resolution for these maps. Attempting additional "refinement" would only misinform. First of all, consider the questionable validity of the averaging methods being used: static climate maps are made by doing statistical averaging over different study periods (usually 12 years long). Algorithms are then used to interpolate data and draw isotherms between reporting stations. So the sample size is quite small, both in terms of the tiny amount of territory the reporting stations cover and the reach of time in the study period. The USDA map of 1990, therefore, looks different than the 1960 map because, in part, the 1974-1986 examination period used for 1990 did not include many major freeze events in the West. A more accurate way to show an average minimum temperatures map would be as an animation over, say, a 20-year period. That's how climate really is: it's fluid, changing from one year to the next. Think video, not snapshot. It's common to come across pat declarations of hardiness, i.e., "hardy to 28F," but such statements are laughable. Hardiness is not established by winter only. The nature of the growing season, exposure and soil quality have a lot to do with it. A plant hardy to 22F in Palm Springs where summers are hot and winters are dry, might die at 30F in Eureka where summers are cool and winters are wet. Finally, a map is only useful if there is a significant body of literature that will dedicate itself to its use. Sunset may have only its own Western Garden Book going for it, but what a book! After 30 years of using the Sunset WGB, I am increasingly impressed with its accuracy under periodic revision AND...its VALIDITY (the editors understand the limitations of attempts to pigeonhole climate). Many envelope pushers of zone envy along the northern third of the West Coast who have often complained that Sunset was "too conservative" are eating crow after Old Man Winter decimated their marginal plants last year. Climate maps SHOULD be conservative.