8 – FROM THE LIVING COLLECTION

PHA’s Collection: Patience, Persistence, Pride by Tim Boland

Silky stewartia at the entryway to the Visitor Center. This 2007 PHA accession was grown from seed collected in Chesapeake, Virginia.

Our commitment to building PHA’s stew- Network coordinates a continent-wide development) causing ever-widening gaps artia collection is based on our founder Polly approach to -germplasm preservation between populations. Hill’s history with the genus and our own among North American public gardens On our past trips to the southeastern desire to encourage the cultivation of these and promotes high standards of collections United States, and my trip to Kentucky last superb small-flowering in home gar- management.” Accreditation as a national fall, we focused on mountain . From dens. As part of our mission of research and collection demonstrates a garden’s enduring nearly 50 separate seed collections made horticultural experimentation, we also bring commitment to global efforts to save . over the last 10 years, only a small percent- a plant conservation focus to , par- Today, over 70 stewartia trees representing age of seed has germinated, and only a scant ticularly the two North American : 22 taxa can be found in PHA’s collections, few have made it into the collections. Why? mountain camellia (Stewartia ovata) and many of them PHA’s introductions. Seed propagation is difficult: the woody silky stewartia (Stewartia malacodendron). seeds take up to five years just to break open! Seed Expeditions Yield New Bounty And once opened, they must still overcome Partnership Leads to National Collection The two North American stewartias, internal dormancy mechanisms to germi- In 2006 we were recognized as co-holding mountain camellia and silky stewartia, are nate. Polly Hill understood this lengthy pro- the national collection of stewartia together endangered in many parts of their natural cess and sowed seeds directly in the ground, with the Arnold Arboretum of Boston, range. In the wild we have encountered patiently letting nature do its work. Massachusetts. Administered by the trees laden with seed and others with no Despite our frustration with growing American Public Garden Association, and seed at all. Conservationists believe the trees stewartia from seed, when, eventually, you now called the Plant Collections Network, exhibit what is called inbreeding depression. meet with success, you experience “stewartia this cooperative program has grown stronger This occurs when small populations euphoria,” as we did this past spring when to become the recognized standard of become isolated over time. Isolation is the two silky stewartia trees (grown from seed excellence in plant collection management. result of habitat fragmentation (often collected ten years ago) finally blossomed! Manager Pam Allenstein explains, “The from deforestation for agricultural use or We collected the seed in their natural habitats: one comes from Winston County, Alabama, and the other from Chesapeake City, Virginia. Found at PHA’s entrance, the trees are an entrancing sight when blooming in mid June.

Propagation Yields Promising Results PHA has been working cooperatively on stewartia propagation with Heather Gladfelter, a researcher at the Warnell School of Forestry at University of Georgia in Athens. We sent Heather seed of S. ovata Natural distribution in North America of silky stewartia (left) and the mountain camellia (right). Maps courtesy of the Flora of North America ‘Red Rose’ and S. malacodendron ‘Delmarva’ in 2013. She extracted the embryos and grew them in a Petri dish using plant growth reg- Stewartia Serendipity PHA Designated as Registration Authority ulators to encourage the formation of roots While extraordinary efforts to grow stew- PHA director emeritus Stephen Spongberg and shoots. This technical process called tis- artias take place, sometimes you just get produced the monograph on the genus sue culture has been used to propagate plants lucky and find a remarkable seedling with Stewartia in 1974. This publication served that are difficult to grow by more traditional enough merit to become a new introduction. as the authoritative resource for much methods like cuttings. Heather has produced I lucked out in 2006. When weeding close of our work. In 2015, then curatorial intern dozens of plants using this procedure. to S. ovata ‘White Satin’, I discovered a Victoria Stewart used Steve’s monograph At PHA, Plant Propagator/Horticultur- foot-tall seedling that had sprouted nearby. to develop a web-based pictorial key ist Brian McGowan has been successful with I transplanted the to a full sun location creating a comprehensive resource for the growing certain stewartias from cuttings in my home garden. This stewartia has dark genus. Her work, combined with our efforts including several of Polly’s Asiatic introduc- stems and a burgundy blush to the emerging to research, collect, and grow our collection, tions. In the past we have rooted cuttings, foliage that persists into late summer. resulted in the International Society for however, the following year the small plants Seven years later, the moment we wait for Horticultural Science appointing PHA as unfurl new leaves only to rapidly perish. arrived: the first flowers—white ruffled- pet the international cultivar registration We hypothesize that the cuttings do not als with a stunning golden boss of . authority for the genus. This designation produce enough growth to accumulate the A cultivar was born! I named this exquisite positions us for working with plant breeders, necessary carbohydrate reserves to support tree ‘Inner Light’ in reference to the striking commercial growers, and other arboreta growth the following season. Brian has gold stamens, and in deference to my wife, to further expand the availability and worked hard to circumvent this through Laura Coit, who suggested the name. (See use of this incredibly beautiful group of striking cuttings earlier in the season. In photo on page 1.) Propagation from cuttings trees. addition, the small trees are overwintered in has gone well. Soon this stewartia will be the protective confines of the greenhouse. Stewartia ovata ‘Inner Light’ as rooted cuttings in shared with the wider horticultural world. the greenhouse

Embryonic tissue from Stewartia ovata ‘Red Rose’ is placed in agar with plant growth hormones allowing small plants to flourish without the strong growth inhibitors typically found in the woody seeds of some stewartia. Photos by Heather Gladfelter.