In 1945, Jean and Wallace moved the Stevens Brothers nursery to Bastia Hill, Wanganui. Although the business name remained unchanged, Jean had taken over from Wallace's brother as a full partner. Jean started working on a new challenge: to widen the colour range of tall bearded irises known as amoenas—that is, those with white standards and violet, violet-blue, or purple falls. This involved the difficult task of working with recessive genes in plants with poor germination. In 1949, Stevens introduced Pinnacle, a very fine white and yellow amoena that gained international recognition and became one of the world's most popular iris cultivars. Both the American Iris Society (1951) and the Royal Horticultural Society (1959) granted Stevens an award of merit for its creation. It has been suggested that the originality of 'Pinnacle' would have won Jean the AIS's highest award, the Dykes Medal, if she had been eligible for it. Jean went on to create amoenas in a range of other colours, including deeper yellow, pale blue, plum, and pink shades.