2007 Nepeta 'Walker's Low'
2006 Dianthus gratianopolitanus 'Feuerhexe'
2005 Helleborus xhybridus
2004 Athyrium niponicum 'Pictum'
2003 Leucanthemum 'Becky'
2002 Phlox 'David'
< - 2001 Calamagrostis x acutiflora 'Karl Foerster'
2000 Scabiosa columbaria 'Butterfly Blue'
1999 Rudbeckia fulgida var. sullivantii 'Goldsturm'
1998 Echinacea purpurea 'Magnus'
1997 Salvia 'Mainacht' (May Night)
1996 Penstemon digitalis 'Husker Red'
1995 Perovskia atriplicifolia
1994 Astilbe 'Sprite'
1993 Veronica 'Sunny Border Blue'
1992 Coreopsis verticillata 'Moonbeam'
1991 Heuchera micrantha 'Palace Purple'
1990 Phlox stolonifera