Zone 8b or 9a??? Help!

Did not know where else to post this. I have checked all over the web and have a very hard time getting an answer. I live in San Antonio zip 78240 and some sites have me listed as 8-b and some 9-a. The Arbor day site says 8-9 (lol, what does that mean?). Anyone know of a sure fire way to tell. I like palms and cycads and many that will grow in 9 will not in 8 so it is of importance to me.

when i am choosing plants i get plants that are hardy for z9 for summers and make sure they are hardy for 8 too for winters, if that makes any sense lol.

got you...a plant rated 3-8 would have trouble in the summer and a plant rated 9-11 would have trouble during the winter so I need plants rated both 8 and 9.

yes lol. i have found tx. is very extreme with the hot and cold. when i do get 8's i make sure they get afternoon or filtered shade and that seems to work it is just trial and error with a lot of plants so don't be afraid to try different things. i just try not to spend too much $$ on my experiments lol.

Why not ask your county extension agent?

i don't know about san antonio but our agent doesn't know diddly. he is a good ole boy who got voted in because it's who you know not what you know. everytime i went to talk to him it turned out i knew a little more and i don;t know diddly lol. even the sheet they give you with planting times is a loose guide line. it is really sad because he is a nice man. but hopefully we will get someone in some day that knows.
and what he did know was pesticides and watermelon. and okra. i shocked him a few times with what i was growing and how. even dropped off info. i got off the internet.
agriculture is a dying breed around here.

It's probably because your zipcode straddles the line on the new map. The northwestern third of Bexar county is Zone 8 & the rest is zone 9. I guess it just depends on if you want to take the chances with zone 9+ plants overwintering. Whatever you choose, you will probably only have to take the chance of losing it every 10 or 15 years.

As far as zone 3-8 plants making it through the summer, I don't even take that chance very often up here in what was previously known as 7b. Our zone 8, is usually a lot hotter than many other zone 8 places. Especially in the dry caliche you probably have there.

Check this out:

http://www.ahs.org/publications/heat_zone_map.htm

The USDA system is based on minimum temperatures, the AHS system is based on heat.

Nope you got it all wrong! You are somewhere in the 28 to 30 zone! http://www.sunset.com/sunset/Premium/Garden/Climate/BGClimateMap10e.html and http://www.sunset.com/sunset/Premium/Garden/Climate/BGClimateZone16to30p8.html#Anchor-ZONE-363

I really don't think this zone thing is set in concrete, they just redid the zone maps last year and they will likely do it again. That may be the reason you get two different numbers at two different sites.

You also need to consider the location on your property, sheltered up against a south facing wall you might be able to drop 1 or even 2 zones. Add a lot of wind and you might not even make the zone you are in.

As far as I know the Sunset climate zones don't have the same credibility outside the west coast, yet. :-)