Zone/hardiness info for trees - who's correct?

If I Google a particular tree species I get conflicting info regrading zone and hardniess. Is the info listed here on Dave's Gardens always correct? Any one place with the correct info that you have found? Or, if there is a conflict, should I just ask here about that specific tree? I have many books about trees and they do not agree on the zone either. Living in 4B, it can make a big difference to me. Yes, I know it sometimes on micro details.

My understanding is that info on DG is often incorrect or misleading. Members add info as they get it. I would check with your local extension and ask them. They'll have zone info and other things they can help you with.

Well, since you asked - I'm right.

Other than that, you can always consult respected time-tested sources like Cooperative Extension (as kwanjin notes); university, arboreta and botanic garden collections from your zone; and textbooks that cover woody plants like Dirr, Bailey's, Krussmann, Hortus Third, etc.

Usually, the accuracy you want is found from sources that don't have an interest in receiving money from you. Many plant sellers don't wish to restrict their clientele, so you may be encouraged to give one of those Araucaria araucana a shot up there behind the Cheese Curtain...

Another thing you might try is drive around your neighborhood and see what's growing well there. If you find a tree you like, talk to the owners.

(And VV is ALWAYS right!)

You raise an interesting question. The tags on plants do vary, I see it all the time. One website will say zone 6, the next will say zone 5, and so on. Sometimes it is a misprint--I bought a corokia once and knew I'd have to overwinter in the garage because I had researched the plant. Then at the end of the summer, I looked at the tag, which said it was hardy where I live. Like a fool, I believed the tag and left it out, and it died. This spring, I loved a conifer at a nursery and it had two tags--one from the grower said zone 5, the one from the nursery said zone 4. I asked the head nursery manager and he said he is confident the plant is a solid zone 4, he has sold it to that zone for years with success, and would guarantee it.

So there is the simple misinformation or mistake, and there is the difference of opinion about what a plant can take. You will never find one place that has the definitive answer.

I'm a 4b like you, but it has been so long since I've seen temperatures that low in the winter, I've graduated myself into a 5a global warming fantasy land. And it is working, the winters have continued to be mild. The selection of plants you can grow in 5a seems about double what can grow in 4b, so I understand where you are coming from. I'd say if you love the plant, it doesn't hurt to pick up some 5s, but try to pick protected locations. There are lots of micro climates on anyone's property. If gardening were a sure thing, it wouldn't be half so much fun.

Yes, I do have some 5A trees that have lasted for years so far - fingers crossed. As far as the local Univ. Ex. people = last people I would ask, sorry. Have had nothing but bad experiences with them. Once I had a tree on my property that I could not ID. Called them and they said bring in a bit and we'll ID it for you. I cut off an entire branch complete with blooms, etc. Dropped it off waited a week, no response. Called and they said sorry, we forgot, bring in another sample. I did and as I stood there they went on line to a tree ID site - same site I could have gone to myself. In the end they said they do not know. A year later I moved to a different county and went through the same experience with the U. Extension agent there, sigh.

I just bought a tree that has the grower's tag on it saying zone 3. Got home and most all internet sites say zone 5.

Sorry to hear about your extension ofc. Maybe the local university? Do you have arboretum close by?

There is no 1 place to get accurate zone information other than to see all the local gardens and talk to experienced people in your area. I'm zone 8b and so are parts of Florida but we are completely different. Sometimes I cringe at the zones put on labels for plants at work as I know they are false. Sell, sell, sell. Some botanical gardens have help lines with Master Gardeners who may have more practical experience, or access to information that is accurate. As VV mentioned, Araucaria araucana does quite well here but not so good towards the east with hot summers but same zone. I bet it would fry in no time in Florida 8b. Have you asked around in your regional forum for advice?

Unfortunately, there are no little signs attached to all of the trees growing in the wild to let us know the minimum temperatures they will tolerate. You'd think that evolution would have taken care of this dilemma, but unfortunately, it did not. (:o)

Just because a plant grows in a certain area does not mean that it will not grow in either a much colder or warmer place.

Chionanthus virginicus is a good example of this. Chionanthus is completely hardy here in Minneapolis, MN, USDA zone 4a, but it is not found native anywhere in this area, and I believe you have to go quite a bit farther south to find native stands. It may have grown here at one time, but the glaciers, etc. moved it farther south. I have both a male and female specimen in my backyard and they are doing just fine, thank you.

Same is true of Baldcypress (Taxodium); there are a few Baldcypress growing in the northern suburbs of Minneapolis, but you don't find natural stands until you get to southern Illinois. The Baldcypress growing in the northern suburbs of Minneapolis have seen temps of at least -35°F in the past 40 years (the trees were planted sometime during the 1960's.) and back then we had true winters - not the wimpy winters we have now. (the trees could have seen temps much colder than -35°F)

Plant and seed provenance is important, but unfortunately, most nurseries do not know where the trees and shrubs they are selling were collected. You just have to take a chance and try it.

I've had a Metasequoia (Dawn Redwood) in my front yard since 1998 or 1999 and it has done great. This spring it started to leaf out and then something happened and now it's dead. I'm bummed the tree died, but now I have room to try something else in that spot. It's all a learning experience.

You won't know until you try. Just do some thorough research on the web before buying a plant and then give it a try.
Good luck,
Mike