I can't give you one site that is totally reliable for every answer but I would suggest your check with your local extension office for guidance. The problem you're encountering is widespread and I've run into it more times than I can recall.

One thing to learn about is micro-climates. I live firmly in zone 7 but I can grow zone 8 plants in a foundation bed on the south side of my house. It's warmer there and more protected so plants with zone 8 requirements do well there. But on the northern side in the shade I've lost zone 7 plants from cold!

Also, different varieties of plants may be more or less cold tolerant than others. For example, all hibiscus do not have the same cold tolerance. Exposure to cold winds during the winter months also plays an important role. Sheltered locations will give a slightly higher zone than tops of ridges or open fields. Add to that the fact that zone 5 sun is not the same as zone 7 sun which is more intense and it can become totally confusing. A completely accurate guide that took all the variables into consideration would be huge!

In short, help from local experts is always good and study YOUR yard for these spots that are warmer or colder, more or less protected. Then check with a GOOD local nursery, (not the big box hardware stores) and they should be able to tell you which varieties are best for your area. And remember that the so-called experts have plants die, too. I've been gardening for over 40 years and I still kill them regularly. But I learn something from every one of them and it's always fun to push the limits and experiment.

Welcome to a fascinating and endlessly varied hobby and good luck with your plant selections.

Sandy

Since information you find on the Internet is not regulated, anyone can write anything. Some of it is accurate, much is not. And even information available on GW is tempered by personal experience and local conditions. As a new gardener, I'd suggest you locate a good regional gardening guide. Sunset publishes a number of regional gardening books for various areas of the country and the information contained in them is very good, although coded with their own zone system which is much more detailed than the USDA zonal system. I'd also encourage you to locate a local garden club or even a friend or neighbor who is an enthusiastic gardener to become a garden mentor. As Sandy notes, local information is going to be the most meaningful for you.

Thank you for the help and information I am on my way... :)

Keilamarie

Keep in mind that the person doing the writing is doing so based on specific zones or areas of the country. In the South, a plant that grows in shade will most likely take more sun here in northern climates. So I always take what I read on the internet with a grain of salt.

Try and find a good source of local information, starting with your local extension office, then reading books specific to your area or zone.

Good luck!!
Shannon

Maybe you can find a local gardening group to join. Members can be a wealth of information. Keep in mind that everyone also has their own biases and their yards are not your yard.

Also, it's fun to once in a while step back and realize we're talking about plants, not brain surgery. Not to make light of your questions! I think part of the joy of gardening is trying things out and not worrying about getting it perfectly right the first time.

Our Extension office is very adamant about our MGs getting their information from an accredited source. We go to state universities such as Penn State and Ohio State to find reliable up-to-date information. I've also used Cornell's site as well as West Virginia U. Choose the state university closest to you and do a little searching. This way you can count on the information being correct and appropriate for your location.
Carol

...it can also be incomplete and/or contradictory.

In my "official" MG capacity I uphold the agreement I made when joining about what type of information to share. I usually try to include a "disclaimer" that I'm providing research-based information, but that doesn't mean it's the entire story.

I've found extension publications that give advice or information completely the opposite from other pubs from the same extension service. I've also pushed the envelope and placed plants in conditions contradicting the recommended ones and had them thrive.

I know personally and anecdotally from other gardeners that exceptions abound. I feel I would be doing a disservice to anyone not to tell them that research-based is not the last word on a subject, just the most recent information we have to share. If they are a bit adventurous they might have a bit of fun and be enjoyably surprised.