Lilyfinch, check out the Lavender Twist redbuds! Ohh, la la!
I have a smoke bush limbed up, it could have been limbed up much taller - it's easy, and you can thin the canopy whenever you like.

Try a heptacodium! I love mine - it's fabulous to have a flowering tree in late August and September! Mine never develops the colorful calyxs that they are supposed to but it has great winter presence with the tan peeling bark making it show up well against an evergreen tree behind it. I got mine as a small shrub with 3 main stems. I cut off two of the stems so I could grow it as a single-trunked tree. It grows quite fast. Because they were introduced only in about 1980, the mature height isn't definite, but 15-20' seems to be the best guess. Mine was planted about 8-9 years ago and it is 10-12' tall.

Here is a link that might be useful: heptacodium - history of...

Try a heptacodium! I love mine - it's fabulous to have a flowering tree in late August and September! Mine never develops the colorful calyxs that they are supposed to but it has great winter presence with the tan peeling bark making it show up well against an evergreen tree behind it. I got mine as a small shrub with 3 main stems. I cut off two of the stems so I could grow it as a single-trunked tree. It grows quite fast. Because they were introduced only in about 1980, the mature height isn't definite, but 15-20' seems to be the best guess. Mine was planted about 8-9 years ago and it is 10-12' tall.

Here is a link that might be useful: heptacodium - history of...

AARRGH! double post - happens when you hit 'refresh' after you step away from the computer for a while, having left GW on the posted message page! Sorry about that....

GGG, do you have the redbud? That sounds like a very nice little tree.

Lilyfinch, you can't go wrong with a heptacodium. They are a very handsome, interesting shrub that you won't find in every garden.

You didn't say if it would be planted in full sun or partial shade? Here are a few suggestions.

Hydrangea 'Tardiva' gets to be about 10X10.
Oakleaf hydrangea also forms a nice, large shrub and the leaves get incredible fall color.
You could also look into different viburnums. Look in the V. plicatum group. Either plicatum plicatum (snowball-type flowers) or plicatum tomentosum (lacecap flowers, like maresii). You can easily limb them up, but if you have 15' in width you have plenty of room to let them be a nice large shrub. I'm not sure there is anything more beautiful than one of these in full bloom, followed by berries (depending on selection-some are sterile) and then fall color. Nice hozontal structure to the shrub. Or there's V. burkwoodii (carlesii) that has a wonderful flower smell.
Callicarpa (very small lavender flowers followed by purple berries all along the branch)
Hibiscus syriacus (rose of sharon)
Physocarpus opulifolius 'Diablo'
Calycanthus

Here are a few small tree suggestions to ponder. 15' tall is a bit of a tough height when it comes to trees. Some of these may be slightly taller but very interesting in the landscape.
Styrax japonica (nice little bell-like flowers)
Amelanchier laevis(white flowers in spring followed by berries for the birds)
Aesculus pavia (very neat reddish flowers)
Chionanthus virginicus (fringe tree-nice white flowers followed by large grape-like berries if female)
Oxydendrum (beautiful more upright tree gets white flowers similar to andromeda at the same time as burgundy-red fall foliage)
Crataegus (hawthorn-I have a washington hawthorn that grows very upright and gets white flowers followed by orange berries that the birds, squirrels and chimpunks love)
Stewartia (beautiful bark and amazing fall foliage)
Magnolia stellata
There are some short crabapples out there too.

I would love to see a picture of your 5 Limelights lined up. I bet they're beautiful!

Wow, i am so glad i asked about the trees! What great responses. I love the idea of the heptacodium. It reminds me that i admired a royal star magnolia that smelled divine in bloom. Im going to look further for an online source of the hiptacodium ! Ive seen redbuds in the store before, ill have to read about them as well. And the hawthorn sounds intriguing too! Im so glad youall could help me. I feel so inspired now!

Thyme, ill be able to share pics of the limelight hedge next year...they were a 3dollar deal from lowes, missing most leaves and my dh accidently wacked one down when the weedwacker bounced off the fence! Whoops. Its regrowing leaves but its a sad plant now!

I have a small weeping pussy willow. It's adorable! Easy to care for, stays very small and makes lovely little flowers in spring and soft pussy willows in fall. :-) Plus, it has a perfect weeping habit.

I've never heard of a small weeping pussy willow, scully! Only the GIANT ones!!

I do not have the lavender twist redbud thyme, but my neighbor does about 4 doors down. It's beautiful for the weeping, heart shape foliage. The flowers are interesting in the spring too because you can really see them along the stems since the whole habit of the tree is to show you it's stuff.
There are also many columnar trees now developed that throw little shade. I've had more trouble finding out about those cultivars since they seem to be bred by many of the smaller nurseries who are catering to a local urban market - the trees are really bred for narrow urban spaces but are useful in other areas as well, such as places you don't want shade thrown!

I have a pansy redbud that I absolutely love. It has beautiful purple flowers in spring and then heart shaped burgundy or purple leaves all summer long. I just love this tree. Mine was a twig planted 2 years ago and is about 8 feet tall and 4 feet wide now. So pretty.

Carol

No one mentioned a pagoda dogwood which has a lovely light green foliage - a shade tree. It will grow to 15 feet but can be kept short like a bonsai. I say it's perfect for a tree grown near a sitting area.

I also have a Harry Lauder's walking stick and just enjoy it immensely. Its twisty branches can be used for floral arrangments and it looks really nice in winter.

I also have the Royal Purple smoke bush which can be trained as a tree.

Also I've just planted the Hakuru Nishi willow which again can be trained as tree. Its otherwise known as a dappled willow.

Oh-- last yes I have the Canadian Redbud tree - simply adorable but this year I had problems with possibly a leaf cutter bee that took out rounded cuts off the edges of young leaves.

I really like ornamental fruit trees like: Pomegranate (you can get actually fruiting or not, and varies in size...), sakura (flowering japanese ornamental cherry),... and like sakura there are flowering peaches and flowering plums, too. A lot of them stay smaller and have a lovely branch structure if they loose their leaves in winter.