I doubt anything.
Their roots are fibrous and too dense to allow anything to actually get its own roots established.
Maybe someone else has some ideas but i can't think of anything at the moment.

you could try Anemone Blanda or lily of the valley, i used to grow that under our 25 foot pines a few years ago. if there is some bright area try crocosmia lucifer if you dont mind it spreading. good luck.

Thank you for the suggestion, will look them up in my gardening book and av a go ...annie.

Euphorbia amygdaloides copes with dry shade. You could try ivy as a ground cover - it may go up into the trees and cover the bare trunks.

Are they your Conifers or the neighbours?, either way could they be topped and the canopy overhang cut back, but not into the old wood, A good plant however for dry shade is Symphoricarpus, known as the Snowberry, its deciduous, but lovely white largish berries through the winter, the flowers are small and pinkish white in colour, julien.

Cyclamen hererifolium or coum, Symphytum grandiflorum, Hedera helix ..... mmmmmm .......