How to use it. Because of their medium size, Knock Out roses complement any landscape and are perfect in perennial borders and container plantings. They also combine beautifully with other flowering plants, provided you choose those with similar sun and water requirements.Daylilies (Hemerocallis spp, zones 3 to 9) are perfect spring/summer complements, as are purple coneflowers (Echinacea purpurea, zones 3 to 9). For a nonblooming partner, choose lamb's ears (Stachys byzantina, zones 4 to 10). For a great autumn companion you can't beat Mexican bush sage (Salvia leucantha, zones 8 to 11).