Jan de Graaff, 86, a horticulturist known for making the once impossible-to-grow wild lily a household garden favorite. De Graaff was at the vanguard of the movement to propagate lilies commercially. Beginning with his first lily experiments in 1938 at the Oregon Bulb Farms, in Gresham, Ore., De Graaff worked on hybrids of lilies that would be beautiful, hardy and easy to grow. Before his efforts, lilies generally were dug from the wild and transplanted to the gardens of Europe and the United States. The wild flower was considered delicate and temperamental, and was thought to require special conditions and exotic planting schemes. He was a native of Leiden, Netherlands, where his family had been in the wholesale bulb business since 1723. In New York City on Saturday.