Dwarf Japanese Cedar (Cryptomeria japonica 'Globosa Nana'). A superb selection that retains a neat, dense mound with little care. Enjoy as a single specimen or group as a filler. Fine-textured foliage breaks up the bold effects of large-leaved plants. Foliage becomes rusty red in winter. Evergreen. Slowly forms a dense dome 2 to 3 ft. tall, slightly wider; 4 to 8 ft. tall with age.
Ferns, black mondo grass, and the hakonecloa (Japanese forest grass) make great plantings at the base of rainchains - they'll thrive with the added moisture! And the river stones will help prevent muddy splashes - as well as (w/ some grade management) disburse any rainwater that might pool there... All this while enhancing the near-by patio! What a well-planned design!