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.