Hi there,
I lived in Johnson City for 40 years and gardened there for 20 of those.
The soil is typical Appalachian - lots of clay with some rock. The rock is mostly limestone with some shale on the eastern side of the city limits. The clay is not the red clay type in Middle TN (or further south). It tends to be a beige color and rather heavy.
Having said that, I always found that the local soil responded well to amendments. Manure or compost does well for the average garden plant and peat moss does very well for azaleas and rhododendrons. As with most of the southeast, azaleas are planted in abundance. Most types will grow very well and bloom faithfully. You can also grow almost any rhododendron and even mountain laurel in the area (if you have some shade).
The whole state is fairly high in rainfall and the humidity is high. On the plus side, the summer temperatures in Johnson City are somewhat lower than most of the state and rarely stay in the 90's for more than a day or two at a time. The elevation (1650-1800 feet) is high enough that some plants that won't grow well in other parts of the state thrive there (area is Zone 6).
The generally accepted safe-planting date is May 10. You can usually expect damaging frosts again by the end of October. The growing season is short but by selective planting you can have something blooming early and late.
Crape myrtles are not a good choice as they may be killed back but they can be grown. Southern magnolia grows - it may be little slower than it is further south and west.
The real performers are the slightly more hardy plants like roses, peonies, poppies and the like. I have even known some people to grow lupines successfully. They are not as nice as those in cooler areas but are respectable. I even used to grow delphiniums every year just because I love them. They bloom well in May and drop dead from the heat in June. They are definitely cool season annuals.
As far as roses go, you can plant better selections there than those I grow here in zone 7. I grew quite a few antique roses (you know, the kind that smell good). You will have to treat for black spot regularly but mildew is not a problem.
If you have any specific favorites ask about them and if I've grown them I'll tell my experiences.
I may have forgotten to mention it but the area is wonderfully scenic if you like mountains and clean lakes.

Hi Steve,
It's nice now that I know what to expect. And I'm excited that there isn't too much rock. I know now to stay away from the east side of the city. Where I live now, a small town named Graham, in western Washington State, has rock held together with a little dirt. Very little dirt at that! How is the drainage with all that clay? I sure would rather amend soil than deal with rock.
I really appreciate all the time and effort it took for your wonderfully informative post.
Thanks so much from one gardener to another!
Carole

Carole,
East Tennessee is called the Valley and Ridge province. The valleys are underlain by limestone and similar rocks. Some clay accumulates that is weathered out of those rocks and in bottom land there may be stream deposits from streams that have flowed through the area. Some valleys are on the Sevier Shale...sometimes it makes a very thin soil.
The ridges and their sides are made up of sandstones and siltstones and often have very little topsoil on them.
The Smoky Mountains are made of much older rocks (geologically) and have built up great soils over time. But if logging or mans' other uses disturbed the soils, those soils are now on their way to New Orleans.
I'm about two hours from Johnson City (much closer as the crow flies) and on our farm we have at least five different soils, not counting the very thin soils on our bluff and in an area called (correctly) Rocky Narrows.
You will rejoice that spring comes much earlier.
You will wonder why evergreens are not as interestingly used in landscaping.
You will wonder why perennials aren't as popular as they were back home.
And if you look, you'll find lots of gardeners just learning to turn our slopes into gardens, because very little land here is truly flat.

Thank you for the additional information. We're going to go to the area this summer. I'll check it out.
Thanks again,
Carole

I heard there is some good racin' up in those parts too ;).

Rebecca

Rebecca,
Racing? Horses, cats, frogs? Sounds like fun. Let's go!

Carole