Surface cover/interest for container Jasmine

Hi.

We've bought this huge planter, it's about 6ft x 18", about a foot deep, and has a massive trellis attached to the back.

I did a bit of investigation, and have decided on Jasmin as the main climbing plant. I've bought two for each end, and I plan on zoning off the ends from the middle, so that we can grow things like tomatoes in the summer months, in the long middle section, without disturbing the jasmine's roots. So it'll be three zones, a foot/18" either end and 3 - 4ft-ish in the middle.

So they'll be planted at the back, to grow up the trellis, but with the planter trough being 18" wide/deep, that's going to leave a lot of bare soil on display in front of the Jasmines.

Is there anything I can plant on there, that will provide evergreen ground cover, very shallow, that won't set down deep roots and interfere with the Jasmine? I was thinking about rockery type plants.... any ideas? Thanks.