I have a slope above the leach field for our septic that I want to plant some sort of ground cover on. I would like it to be something that will help hold the hill in place but at the same time not have a terribly invasive root system because of the leach field. It can be flowering or not but I would prefer something that either flowers or has variegated foliage. Can anyone recommend a good ground cover for me? I live in northeastern Washington state near Spokane. Our winters can get fairly cold, we're in zone 5 in most of the seed catalog zone maps.