Thrillers, Fillers and Spillers. If you are new to container gardening, you may find this Container Garden Basics post helpful. I wrote it for Buchanan’s Native Plants this week. It was a fun post and I have a really pretty container on a pedestal in my garden now. The basic premise is creating a lush container garden using the principle of three. The thriller plant stands out, the filler “fills” the empty spaces, and the spiller “spills” over the rim of the pot and flows down.