Born in Grossheppach, Germany, Ellwanger apprenticed as a nurseryman in Stuttgart, before immigrating to the United States in 1835. After settling in Rochester, New York, he joined the Reynolds and Bateham Rochester Seed Store and Horticultural Repository as a nurseryman. In 1838 Reynolds and Bateham terminated their partnership, and Ellwanger bought the business. In 1840 Ellwanger partnered with Irish horticulturist Patrick Barry to establish Mount Hope Nursery. Together, Barry’s knowledge of fruit culture and Ellwanger’s knowledge of European horticulture helped the nursery achieve early success and recognition. In 1841 a ruinous hailstorm and fire forced the partners to rebuild by expanding their sales outside Rochester, leading the nursery to more than double in size within two years. In 1843 the nursery published its first catalog: Annual Catalogue of Fruit and Ornamental Trees, Flowering Shrubs and Plants, Bulbous Flower Roots, Green-House Plants, etc., Cultivated and for Sale at the Mt. Hope Botanic Garden and Nursery, Ellwanger & Barry, Proprietors. A year later, Ellwanger traveled across France and Germany to collect new specimens of trees and plants for the nursery’s collection, leading the business to publish a second catalogue. The Mount Hope Nursery became a leading supplier of flowering trees and plants to the western United States. By 1871 the nursery had expanded to 650 acres, in addition to opening new branches in Toronto, Canada, and Columbus, Ohio. Apart from being the largest nursery in America, the business became internationally renowned, accepting orders from as far away as Japan. Ellwanger and Barry also worked to improve their Rochester community, donating 22 acres for the development of Highland Park and beautifying Rochester’s Mount Hope Cemetery. Ellwanger died in Rochester at the age of 89.