Sometimes a single flower evokes the unique and fragile quality of a plant collection : a tree peony , its drooping pink petals wet with rain , photographed by Roger Bruce at Linwood Gardens in Pavilion , N.Y. The garden is part of a country estate built by William H. Gratwick II , whose son William III worked with A. P. Saunders , a chemistry professor and peony breeder at Hamilton College in Clinton , N.Y. , to create new tree peony hybrids that sold worldwide .