Not much grows under holly-poor light,too dry etc-but more info would be useful?
I have several holly trees, and not even weeds want to grow there.Often the branches of holly trees reach down to the ground, so the entire area is effectively covered by low branches.Ivy will grow there. Ivy never tries to climb up a holly tree, but merely covers the ground.Unlike most trees, holly is evergreen, so the ground never sees sunlight, so you can't grow Spring bulbs.
I have a holly hedge and weeds seem to manage very well under there. As you can imagine it's a pain to clean up so we're going to have on last good go and then put down weed suppressant fabric and chipped bark.
If your holly is a tree or large bush and you can raise the crown by removing lower branches you should be able to get some plants growing. Improve the soil with a thick mulch of good garden compost and or well rotted manure now and leave it till spring to plant up with things like geranium macrorhizum which copes well with dry conditions, has pretty white or pink flowers in May and scented foliage which is usually evergreen. It turns a glorious red in autumn and lasts through winter. You just need to pull or cut off the tatty bits on spring.
In old house we had a very large holly.
I lifted the crown by removing the lower branches. It ended up looking like a tree. Then I tried all sorts of undercover.
In the end the most successful was cyclamen and I plalnted up about 8 erysinum (perrennial wallflower) Bowles variety and as they tolerate poor soils etc. They didn't die and gave easy to keep interest all year.
I grew them from own cuttings as they take very easily and don't take long to establish once planted out
I'm another who has removed lower branches.
Varigated ivy, nearest the stem. G.Macrorrhizum & G.Nodosum both cope. Tellima Grandiflora too. These can all be planted into 'pockets' of better compost nearer the edge of overhanging canopy & that gives them a good start. All more or less evergreen, with the geraniums having good Autumn colour & the bonus of flowers.
Small bulbs eg Muscari will also cope at the canopy edge.
Like the cyclamen idea.... J.
Well Rona--does any of this help?-it would be nice to know