Answer: Here are a few cold hardy suggestions for your planter boxes:
Coral bells; Sedum; Ornamental Grasses; Lambs ear; Ivy; Creeping Jenny; Hens and Chicks; Flowering cabbages; Swiss Chard; Sages; Pansies; Primroses; snapdragons; Creeping wirevine; New Zealand Flax. Since you're in zone 10 where winters are mild, you might also include parsley, chives, cilantro, geraniums and trailing fuchsias.
Best wishes with your container gardens!
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