That's a tough one. Maybe Paperbark maple, but they grow wider than that. Some flowering cherry cultivars can be quite narrow. You'll find quite a few conifers that would fit that size.

I'd consider red vein enkianthus, Enkianthuis campaulatus. Not only is it a great and rather under-used shrub, but it fits your sizing.........generally about twice as tall as it is wide and with branching that appears to be in tiers. Nice fall color but winter interest is marginal.

I might be considering either training , fruit trees in particular or pollarding - hornbeams for example, respond well to ornamental pollards. Why the limit of space? Current soil and aspect?

For use as a border to berberis hedge. Soil is loamy clay - neutral. Well drained. Basically looking for a contrast in form to the berberis hedge which will be about 4 ft tall and deep. I need something "leggy", stalky, you know. Been thinking recently of some of the dogwood shrubby forms - some have colored twigs that show in winter. Might go with that even though it's not as tall as I'd like - there's good contrast of form and color to the berberis.

Bodnant viburnum, if suited to local climate and soils. Already in bloom here in USDA 8.

http://www.monrovia.com/plant-catalog/plants/2189/pink-dawn-viburnum/

Amelanchier alnifolia 'Obelisk' (Serviceberry). Also, Slender Silhouette sweetgum gets much taller but stays very narrow and is beautiful -- maybe you could keep it pruned to the height you need?

Sheptn, what are you trying to do with this shrub? What role do you want it to play?

Can you show us a picture of where it will go and why?

I like Enkianthus campanulata very much also.

Here's a Fall picture of one of mine taken a few weeks ago. It would be much redder if it were in more sun. Looking west and surrounded by trees. It's about 15 or 20 years old.

Mike

Have you already planted the Berberis hedge? If not you might want to reconsider planting an entire hedge of this. I grew up with a Berberis thunbergii hedge in z6 OH, and IEM due to the thorns it was uncomfortable to prune, caught every leaf and piece of blown trash in the neighborhood (so needed frequent cleaning), and made walking barefoot in the yard impossible since it shed thorny twigs. It was homely in winter with a densely twiggy form decorated with whatever had blown into it in the last few days (lots of oak leaves!) I think individual Berberis mixed with other plants for your hedge would be both more attractive and more pleasant to maintain if you choose to plant Berberis. Berberis thunbergii (the most common species found in nurseries) is considered an invasive exotic pest plant in TN, though there are native Berberis in the US. Invasive means that birds eat the berries and spread the plants into wild areas when the seeds pass through their digestive systems, though you may never see a volunteer in your yard. Here in NH I have quite a number of B. thunbergii in my woods (along with buckthorn, honeysuckle shrubs, and bittersweet), so I am always appreciative when folks choose not to plant invasives.

I like Enkianthus as well, but it's a member of the Heath family, so I am not sure if it will be happy in your neutral soil. I grow it where the soil is acid, and though smaller than Mike's (at 8 years or so in a colder climate), mine looks quite similar. I like the somewhat layered look to the plant in winter, but I don't know that it would contrast much with the barberry.

In addition to colored twig dogwoods, you might consider some of the dwarf forms of fruit trees, such as weeping crabs or cherries. I am not sure if there are any that will stay as narrow as 5', and you might want to check for disease resistance as part of your search. I have seen some Japanese maples with narrow form, but I don't know specific varieties, nor how tall they ultimately will get.

Many Berberis are invasive in many places in the NE Us too BTW.

+oM

Thanks for info re: invasiveness of berberis. I will check into that. And I think a narrow weeping habit might be just what I want. Appreciate all the feedback.

Tom, Norway maple, Berberis thunbergii, and the non-native Euonymus burning bush are all forbidden in NH to sell or trade as of several years ago due to their invasive nature. I think they should have added a few others as well, such as smooth buckthorn and Asian bittersweet.