|I have just put in a hedge of arborvitae. They're in full sun most of the day. What will grow well at their base? Hosta? Day lilies?|
|I'd choose sun loving perennials such as heather, daylilies, irises, or ajuga (carpet bugle groundcover). While some hostas will tolerate sunshine, they prefer soil that's more moist than your arborvitaes will appreciate.
Best wishes with your garden!