2018 ASHS Annual Conference

Of the 244 threatened (CR, EN, VU) or data deficient (DD) Magnolia species cited in The Red List of Magnoliaceae, revised and extended, (Rivers et al., 2016), only 104 (43%) can be found in ex situ collections. Most of these are present in five or fewer collections resulting in a greater risk of loss. Modern nursery propagation and production methods may be employed to propagate and rapidly grow endangered magnolias that can then be distributed for widespread ex situ conservation. Magnolia sphaerantha (C.Y.Wu ex Y.W.Law & Y.F.Wu) Sima (syn. Magnolia elliptilimba, syn. Michelia sphaerantha), ranked data deficient, is a rare species of evergreen magnolia that grows as a medium tree in broadleaved evergreen forests at elevations of about 2,000 m in central Yunnan Province, China. Until recently it was rarely found in botanical gardens outside China. In early 2014, the UF/IFAS NFREC received 66 seeds collected November 2013 from a grove of wild-collected M. sphaerantha in Kunming Botanical Garden, Yunnan, China. Twenty seeds germinated and seedlings were cultivated using production methods typical of North American container nurseries, including applications of slow release fertilizer and automatic irrigation to plants growing in containers containing soilless substrate. Rapid seedling growth resulted, allowing repeated collections of axillary cuttings for asexual propagation. Cuttings 12-14 cm in length were treated with a commercial talc-based rooting hormone and placed in a greenhouse under intermittent mist. Cuttings rooted in 9-11 weeks at percentages ranging up to 100% depending on seedling clone and rooting hormone concentration. In addition, rapid growth of newly propagated plants allowed additional cuttings to be collected from the initial set of propagules. Within 12 months of initial seed collection, parent seedlings exceeded 2 m in height and a total of 114 M. sphaerantha plants were available for distribution. As a result of these efforts, M. sphaerantha specimens are in ex situ cultivation at 32 botanical gardens and other institutions in 13 North American states and provinces. Similar nursery production and propagation practices are being applied to M. garrettii, M. rajaniana, and M. sapaensis. Preliminary research demonstrated feasibility of cutting propagation from seedlings of M. fraseri var. pyramidata, a taxon which cannot be propagated by cuttings from mature growth.