But the leaves are a pain - though I have to say, at my old house site that was surrounded by sycamores we never had a weed problem since the leaves made great mulch. I like the sycamores since they are deciduous so you get sun in the winter and shade in the summer. http://davesgarden.com/guides/articles/view/887

Tulip poplars grow pretty fast, are deciduous and have pretty flowers. http://davesgarden.com/guides/articles/view/3765

Both sycamores and tulip poplars get very large so might overgrow your yard. But if you are only panning for the next 20 years, they probably won't be a problem for you.

Do NOT get a silver maple - while they are pretty, they are brittle and tend to break off branches when they get big enough to provide shade.

http://davesgarden.com/guides/articles/choosing-a-tree-for-your-yard

How tall do you want the hedge? We had anise bushes that are evergreen and in ten years got to 20+ feet. They look something like ligustrum but are a lighter green and are not as invasive as ligustrum. (Plus I don't react to anise blooms the way I do to ligustrum.) The anise seeds are NOT the star anise you pay for in the spice aisle. http://davesgarden.com/guides/articles/view/2759/

Use "starter pellets" when you plant it. These are fertilizer pellets which you put in the back-fill, a few inches outside the rootball and about 6" to 12" deep depending on the size of the plant. Go with one strong in Phosphate and Potash which will develop a strong root base.

I had a 24" box African Tulip tree planted at the same time that neighbors planted 15 gal African Tulip and Sycamores. Mine started out about ten feet tall, while theirs were about six feet. Five years later mine is higher than my roof (two story building) while theirs are barely over ten feet.

African Tulip, by they way, is a nice tree for 7a. It is almost evergreen; stays in full leaf all winter, then blooms beautifully in May or so and toward then end of that month drops about 75% of it foliage. Never gets the "bare" look of a deciduous tree though. Sets new leaves in July and is fully green again by end of August. Grows pretty fast if you give it a good start, and doesn't need much water.

Lacebark Elm, aka Chinese Elm

Plant the smallest specimen you can find and as long as it has a decent location it will make a very nice shade tree in short order. After about 10 years it should be about 40' tall and about 25' wide. Fully mature it will be around 60' tall and 40' wide, so plan accordingly. They have a good resistance to Dutch Elm Disease which plagues other elm varietals, and generally have good longevity compared to most other fast growing trees. The leaves are quite small, so they are easy to rake in the fall. It does produce seed pods in the spring, but they don't produce enough mess to really worry about like some other trees. You'll need to prune it each spring for the first few years.

Texas Ash

There are a few different ash varietals. The one I have is a Texas Ash which I planted about 15 years ago and it's about 35' tall and almost that wide. It's a little slower growing than the Lacebark, but still a pretty fast growing tree that makes a very nice shade tree as it matures and also can expected to be disease free and long lived. Like the Lacebark the leaves are small and there's virtually no seed mess to worry about. Fully grown they can get to about 80' tall, so make sure you have a big place for it to mature completely.

Natchez Crepe Myrtle

If you want something a bit faster than those two which doesn't get quite as big, this one is a good choice. This one is actually a hybrid between the Japanese crepe myrtle and the standard western crepe myrtle. It takes a more tree like form and has showy bark like the Japanese varietals, but produces larger and more prevalent flower clusters like the western varietals. I planted one of these about 10 years ago and it's about 25' tall and wide today. I limited it to three trunks. Occasionally you get black mites on the trunks that tend to turn them black, but otherwise don't really affect the health of the tree. They are fairly easy to eradicate, but they don't tend to persist past the winter unless you get them again.

I especially like the white flowers, plan on getting one for contrast. I have some catawba and red rocket (or maybe dynamite, not sure what the name is) along one side of street out at end of the property.

As far as I'm concerned, Natchez is hands down the best of any of them. There are some that produce more colorful and showy flowers for longer periods, but none of these have the perfect form and attractive trunk the Natchez gets from the Japanese varietal part of its taxonomy.

I will certainly check out the others though.

I'm in zone 7b, and a plant in fairly widespread use around here for hedges & screens planted in subdivisions, office parks, etc use arborvitaes. Specifically 'emerald green' arborvitaes (about 10-12' tall) and 'green giant' arborvitaes (30' and looks like taller). Neither uses a lot of area, they are tall & slim and will grow together into a true screen. Dense, tall, very fast growing, attractive evergreen, vertical conic shaped.

If you have a fence, have you considered wild climbing roses? Bamboo might be another idea for back of a yard along a border, grows fast too. Both would do well in 7a.

The reply suggesting tulip poplar for a specimen or shade tree is spot on, I have one in back and its beautiful. Covers in large orange & light green flowers. Slow grower, but it's big and shady.

Good luck with your plants!

That only covers winter hardiness. You also need to account for heat zones for summer stress and consider rainfall and moisture. 7a covers a lot of different environments.

In general, I strongly prefer plants native to the region as they will likely survive the various local stresses and will be most beneficial to the native wildlife. In places like NC, the critical issue for many plants is surviving the "drought" summers that have high temperatures and almost no rainfall from July until October. These happen about every five years and are brutal. (Unlike this year with almost daily rain.)

I don't have any shade tree suggestions without knowing a lot more about your weather and your soils. On the hedge, I strongly oppose bamboo in all circumstances.

For a fast growing natural hedge, I like wax myrtle. It is great for birds and hiding a pesky neighbor or an eyesore. If there is enough room to support the height, I sometimes mix the wax myrtle with red cedar. That provides some variety in the appearance and in the wildlife that is attracted.