Frankly, if the border's only 3 feet wide, that's far too close to the conifer roots for anything to grow. What about planting in pots either standing on the soil of the raised border, or on the edge?

There is one that will grow ... centranthus ruber. Have even seen it IN a conifer hedge! It will definitely provide a 'ruffle' around the base of the hedge, and flowers forever, in shades of white, pink and red, but it also self-seeds everywhere else. If you are prepared to regularly pull up the seedlings (very easy) outside of your hedge line, it could work for you? Another option are some of the variegated euonynous that require little attention - after they have been established, that is - water well initially and until they take off. They can be clipped back if they grow into the hedge, when the hedge is clipped. A good annual is poppies, which will self seed every year.

How about raised planters out of say railway sleepers so you have more choice and automatically hide the base of your trees .

Good idea Noseypotter! Could then be a mix of any shallow rooting perrenials or constantly changing annuals for the seasons.

it would look good out of blocks and face it with natural stone to .

Thanks for the advice everyone. I think raising the front of the planter is the answer and then plant shallow root perrenials. I'll let you know how I get on.

your welcome trinny1 x x .

I'm a little confused about what you intend to do, but if you mean you're going to raise the edge of the border in which the trees are currently planted, bear in mind you must not raise the soil level above its current point around the base of the trees.