An interesting byproduct of planting related species side by side is that pollinating insects can become unwitting hybridizers. Such was certainly the case with one of the Arboretum’s most famous introductions, Hamamelis × intermedia ‘Arnold Promise’. A beautiful and vigorous witch hazel, ‘Arnold Promise’ was named to honor the place where it began, a happy accident of nature.

Arnold Promise witch hazel
Even on snowy days in late winter, the vibrant display of this accession of H. × intermedia ‘Arnold Promise’ (#396-69*A) dazzles.

The story begins in 1928, when Arboretum propagator William Judd collected and grew seed harvested from an Arboretum accession of Chinese witch hazel (H. mollis)—a plant acquired from plant explorer Ernest Henry Wilson’s 1907-09 expedition for the Arboretum to China and Tibet. Nearly two decades later, famed Arboretum taxonomist Alfred Rehder deduced that plants propagated from its seed were likely hybrids, as they exhibited intermediate characteristics of the Chinese witch hazel and its neighbor in the Arboretum landscape, the Japanese witch hazel (H. japonica). With this in mind, he selected an appropriate scientific name for the new plants: H. × intermedia. By the late 1950s, staff observed that one of the hybrid offspring consistently bloomed with larger flowers and over a longer period than the others. This individual was given the cultivar name ‘Arnold Promise’. Although this individual no longer survives, clones of this plant continue to delight late winter visitors to the Arboretum, and over time it has become a mainstay in New England nurseries.

The pleasingly fragrant flowers are composed of a reddish calyx and clear yellow petals, each nearly an inch in length. Even following severe winters, these are consistently borne in great profusion from mid February into March. Come fall, its autumn foliage color is a clear, bright yellow. Unlike North America’s vernal witch hazel (H. vernalis), dead leaves never persist through the winter to obscure the floral display.

Arnold Promise witch hazel
The Hunnewell Building accession of ‘Arnold Promise’ also exhibits the cultivar’s attractive vase-shaped habit with upright, ascending branches.

As if these features were not enough to recommend it, the shrub’s broadly vase-shaped habit and gently ascending stems lend a gracious aspect to its appearance in all seasons. A delightful product of happenstance and the notice of astute growers, Hamamelis × intermedia ‘Arnold Promise’ stands as one of the Arboretum’s great contributions to horticulture. As a harbinger for spring in a climate notorious for long and difficult winters, the promise it keeps is that perseverance is rewarded.

Originally published in the Spring/Summer 2010 issue of Silva.

From “free” to “friend”…

Established in 1911 as the Bulletin of Popular Information, Arnoldia has long been a definitive forum for conversations about temperate woody plants and their landscapes. In 2022, we rolled out a new vision for the magazine as a vigorous forum for tales of plant exploration, behind-the-scenes glimpses of botanical research, and deep dives into the history of gardens, landscapes, and science. The new Arnoldia includes poetry, visual art, and literary essays, following the human imagination wherever it entangles with trees.

It takes resources to gather and nurture these new voices, and we depend on the support of our member-subscribers to make it possible. But membership means more: by becoming a member of the Arnold Arboretum, you help to keep our collection vibrant and our research and educational mission active. Through the pages of Arnoldia, you can take part in the life of this free-to-all landscape whether you live next door or an ocean away.

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