Hi Knutsford and welcome to GoY. How deep is your 'narrow boarder' and what is the size of the garden overall, a photo added to your question would give us all a better idea of what is possible.

In particular, how long and wide is this border you want to plant, and how much sun does it get?

Also, what kind of trees are they? Pleaching is a training technique that can be used with many species, some easier to deal with in small spaces than others.

Thanks for the prompt replies. The border is approx 15 feet long and a very narrow 30 inches in depth. It gets quite a lot of sun and is well sheltered as it has a fence behind it and I believe the pleach trees are quercus ilex.

I'd send a picture but it's a bit stormy at the moment:)

Thanks again.

Hmm, difficult to make something that length and width attractive once planted. Photos would be good, is it possible to widen that border, or at least one or two parts along it?

Unfortunately it's not possible to widen the border as it has been edged with edging stones that have been concreted in and I don't want to go to the expense of digging them out and relaying. It's not something I'd want to try as I'm not handy!!

I will enclose a photo when storm Doris calms down.

Thank you.

Hmmm...Holly Oaks are slow growing and deep rooted, but will need watching with the pruning and training. If they run wild, they will overrun the entire garden, and threaten nearby paving and foundations. Be sure to look up pleaching techniques, since that is an ongoing process.

Would still be good to see a photo of the garden...

You could try a 'shrub-size' Amelanchier, or the even smaller Prunus kojo-no-mai (dwarf cherry) . . . both about 3ft tall with lovely white blossom any day now!