When and where I am not quite sure but would like to find room for :
Spring Colour
Crocus 'Remembrance'
Crocus 'Vanguard'
Erythronium californicum 'White Beauty'
Iris 'Sheila Ann Germany'
Narcissus 'Topolino'
Late colour
Aster x herveyi (previously aster macrophyllus 'Twilight')
Laserpitium siler - long - lived umbifiller - looks similar to orlaya.
Persicaria amplexicaulis 'alba'
Sanguisorba officinalis 'Arnhem' - July/August flowering - good partnership with taller molina varieties
Sedum - 'Jose Aubergine' (possible partners - penstemon 'Andenken an Friedrich Hahn' and salvia verticillata 'Smouldering Torches'.
Further research needed
Hamamelis 'Gingerbread'
Rubus 'Silver Form'
Salix 'Melonostachys'