Once a hebe gets dishevelled, there's not a lot you can do about it. The only way to keep them in shape is to do so right from the start, with regular pruning of the tips. Once hebes gets a bit old and moribund, you cannot encourage them to regrow from old wood. They are quite short lived, too, and it sounds to me like yours has overextended its natural lifespan. So, dig it out and start again, but if it's a hedge you want, don't replant with hebe as it is hopeless as a hedging plant. I don't know why many gardeners baulk at getting rid of plants which have overstayed their welcome. We don't feel the same way about taking up vegetables for the kitchen as we do about our ornamentals. Think of your hebe as a crop, the better to reconcile yourself to its fate.

The above reply is incorrect in almost every respect.
There are dozens of different varieties of hebe.
Some are very good at regrowing - you can let them get completely leggy then hack them back and they will regrow.
Many will also regrow from old wood if encouraged (by having a fair amount of the top taken out or by having several stems removed down low). Many will last for tens of years. All are evergreen. Many make excellent hedgeplants. Generally the lower, slower-growing forms do not regrow as quickly or as well, but at 5-6ft tall you dont have one of those. The way to check whether it is a hebe is to see if the leaves are in pairs directly opposite each other on the stems, with the next pair at 90 degrees. All hebes follow this form, even the tiny alpine ones that look at bit like heathers.
I'd be inclined to give them a good hard prune (but not remove all the green), open them up so plenty of light can get to the base, feed them and see if you can get them to regrow. If this works, take some more of the top out next year and within a couple of years you could end up with a lovely, luscious and fast growing hedge. If it doesnt work, then slash and burn.
Good luck.

Dave, out of interest... have you ever been to County Park Nursery on Wingletye Lane in Hornchurch (Essex)? I know they're renowned for their hebes, and I think there's a cultivar called "Wingletye". I live in South London but my parents live in Upminster, and I'm wondering if it's worth making the trip to the nursery.

I think it largely depends on the type of hebe you have. I had an old large-leaved shrubby one and hacked it down like a buddleia. Seems to have thrived on the abuse and the new growth is much tidier.

You could always post a photo of it to check it's definitely a hebe, too..

Melanie

thanks for all your answers: i think i will put a picture because my mother in law does not think it's a hebe!!! very confuse now!!!

Thanks for the information on identifying a Hebe with regard to the spacing of the leaves. I have puzzled over a 6 foot shrub in my garden for years. I now know that it is definately a Hebe, and it just loved being cut right back last year as it has bounced forth prolifically this year 2007. My problem is that I am moving house and can't take this lovely but very big shrub with me. It is now April. How can I take some foolproof cuttings, so that I still have this lovely shrub at my new address,as I don't know the name of this particular Hebe, in order to be able to buy another one?

Here is a link that might be useful: Piemonte Palms