ARTICLE BY: KATE McMILLAN Kate McMillan is a HPSO Board member and owner of Cultiverity, a garden design company in Portland. When she’s not working on her own or someone else’s garden, she’s running her web design studio, Outbox Online. She can often be found posting to the HPSO Facebook page, Instagram and Twitter feeds, and coordinating this blog. *** You know that person who is always like, “Have you heard about ____? You have to try it!” That’s me with ground cover. I tell everyone about its virtues in the garden, and why not? It’s the answer to so…