Hi- I garden in Seattle, so this might be way off base. But... We have severe drought here every summer, and the cedar trees get huge. Hardly anything can survive under them. So, I do have a few suggestions, I have been playing around trying things under a cedar and a big pine tree:
Short:
Epimedium pinnatum ssp colchicum super tough, bright yellow flowers in spring
Epimedium x Warleyense has little orange flowers
Vinca minor 'Ralph Shugert' which has variegated leaves.
Medium:
Hemerocallis fulva 'Flore pleno' recommended in Graham Rice's book about dry shade. It survives and blooms, might be TOO good!
Alstroemeria 'The Third Harmonic' recommended by Annie's Annuals for dry shade in California, it works here although took a few years.
Taller:
Choisya ternata 'Sundance' a Mexican shrub which I stupidly put under a cedar tree where it never receives even one beam of light. Absolutely fabulous!
