Looking for quick but non-dominant ground cover

[AllInContainers]

I have three upright planters about 12" (300mm) square x about 1m high, and will be topping these off with ericaceous compost and planting Gaultheria Procumben (Wintergreen/Tea Berry/Partidge Berry/Other "common" names). This will hopefully form a nice lush evergreen mat with berris which will slowly creep down the planters .... but very very slowly, and the plants have just arrived arrived in 9cm pots.

I need suggestions of what else I can put in there to give ground cover and look good, but yield to the Wintergreen as it gradually spreads rather than choke it out

Any and all suggestions appreciated

[AllInContainers]

... or would I just be better topping off with a bit of landscaping fabric for now ... ?

[AllInContainers]

Never mind - decision made

A bit of internet searching showed they spread by underground rhizomes, so I'll be just topping off the planters with a light coating of decorative gravel so the plants can push through from beneath and not be hampered by other plants

[johnjohn]

Glad we could all help!

[AllInContainers]

Glad we could all help!

Sometimes silence is a valid and informative answer too