Erysimum Poem Lilac is a long flowering Wallflowers. Poem Lilac has clusters of lilac purple flowers that are really fragrant and will flower from early Spring to early Autumn. The leaves/foliage on the Erysimum Poem Lilac are grayish/green throughout the year. It will flower year after year and if you plant it in a sheltered spot, it will flower for much longer in your garden.