Diane, I don't know anything about your local conditions, but would the so-called flowering cabbages and kales work? They move easily, and so if started elsewhere, could be moved into place once the dahlias are gone. Their color range is narrow, but there is now enough variation in the cultivars to allow for an interesting planting. You didn't mention the area of the planting: maybe you would have to have a fund raiser to pay for enough cabbages and kales. : ) Jim McKenney Montgomery County, Maryland, USA, USDA zone 7, where the ornamental cabbages and kales are not quite hardy enough to survive our typical winters.