Beauty Bush

Arboretum visitors who venture up Bussey Hill road just past the Lilac collection, in late May to early June, have the opportunity to see a young planting of Kolkwitiza amabilis (54-2017*B) also known as beautybush.  This shrub in the honeysuckle family (Caprifoliaceae) is a monotypic genus and garners its common name from the profusion of blossoms that display their full floral elegance in late spring or early summer. Individual flowers, appearing after foliage, are carmine-pink as the corolla expands eventually bursting into their distinctive five-lobed white flowers, beset with a bearded orange reticulate throat. While these shrubs, grown from seed since 2017, are currently diminutive in their stature they have the capacity to grow up to 3 meters (10 ft) in height with a multi-stemmed, fountain-like form and notable shaggy exfoliating bark. For comparison, a near centenarian example of the species (Accession # 18090*A) can be viewed just a few feet away.

Kolkwitzia amabilis is an exceedingly rare shrub found in the wilds of central China with only two known collections of seed germplasm and subsequent introductions into North America. The first collection was made by plant explorer Earnest Henry Wilson who collected seeds of K. amabilis in 1901 in the mountains in Hubei, China. These seeds were sent first to Veitch and Sons nursery in England before making their way to the Arnold Arboretum in 1907 as plants. This marked the first introduction of this species into cultivation in North America and it became a perennial favorite of Wilson, who often lauded its beauty and merit.

Ninety-three years later in 1994, the second introduction of Kolkwitzia amabilis was made into North America from seed collected during a North American-China Plant Exploration Consortium (NACPEC) expedition which included Arboretum Senior Research Scientist Emeritus Peter del Tredici. In an unfortunate stroke of bad luck, the entirety of seed lot from this collection was lost when the plants were accidentally sold in 1997 during an Arboretum plant sale. Luckily seeds from the collection were shared among NACPEC institutions including USDA’s National Plant Germplasm System (NPGS) who had received seeds at the North Central Regional Plant Introduction Research Station in Ames, Iowa.

Staff scientists within NPGS, recognizing the importance of this species from a conservation and germplasm preservation standpoint started a project with the goal of bulking up the total number of available seeds for preservation and distribution. Between 1997 to 2001 seeds were grown out from this collection yielding seventeen plants that were field grown at the station and allowed to cross pollinate. Despite these plants being open grown together in the field this process was considered to be “controlled pollination via isolation” because no other known Kolkwitzia amabilis aside from the 1994 seed lot were present at the station.  Seeds from these pollination projects were collected in 2004 yielding 6,000 seeds and again in 2006 yielding an additional 36,000 seeds. This newly collected seed was then used to bulk up holdings in NPGS for conservation and was made available for distribution. With ample seed to share they were sent to other long-term seed banks for back up including 2,700 seeds at the National Laboratory for Genetic Resource Preservation in Fort Collins, CO, USA and another 500 seeds at the Svalbard Global Seed Vault in Norway.

In 2017, the Arnold Arboretum also received seeds from the Ames Station. After germinating the seeds and growing the shrubs on, six were planted out into the collections, including accession 54-2017*B presented here. This story demonstrates the importance of studying and collecting rare species in the wild and the critical practice of conservation seed banking by the USDA’s National Plant Germplasm System.