Hydrangea angustipetala

Photos courtesy of Michael A. Dirr, Thompson & Morgan,
and Monrovia

It’s certainly not a household word in the world of commercial hydrangeas, but it’s worth integrating into a breeding program. This, along with H. luteovenosa and H. scandens, offer unique traits not available from H. macrophylla and H. serrata.

All produce lacecap inflorescences, fertile flowers with yellow stamens; sepals few and white. Flowers are produced from the nodes, the entire length of the shoot, late April-early May (in Athens, Ga.), before H. macrophylla. My original premise was to utilize this flowering trait with the mophead inflorescences of H. macrophylla to develop hybrids with the appearance of brussel sprouts. Successful hybridization was achieved integrating/introgressing H. angustipetala and H. luteovenosa but not H. scandens with H. macrophylla, although the latter combination was successful by another breeder. Our original premise about the potential hybridization was based on the molecular work of Dr. Tim Rinehart at the USDA Agricultural Research Service.

We believed H. angustipetala offered the greatest opportunity for improvement because of the larger, pest free, bright green, frost/freeze tolerant foliage, which ranges from deciduous, semi-evergreen to evergreen. On March 5, 2006, Dr. Josh Kardos (at that time a University of Georgia Ph.D. candidate), Mark Griffith and I visited Crug-Farm nursery in Caernarfon, Wales, to better understand the variation in H. angustipetala. The owners, Bleddyn and Sue-Wynn Jones, graciously toured us through the nursery. They are intrepid plant collectors who have traveled the globe in search of horticultural treasures. In their garden, nestled in the snow, was a healthy grass-green (perhaps evergreen?) specimen of H. angustipetala. Taxonomically it is impossible to comprehend the variation with Crug-Farm offering approximately 19 wild-collected accessions from Taiwan and Japan including f. formosa, f. macrosepala, f. obovatifolia and Yakushima. I viewed flower photos of all on the web site (www.crug-farm.co.uk), and the common denominator was the yellow-stamen fertile flowers and the white sepals. Flowers are fragrant to various degrees. Sepals were borne 3 to 5 in a cluster, serrated, incised, or entire, elongated to rounded, from few to many surrounding the fertile flowers.

Some were collected from elevations between 7,000 and 8,000 feet, so it’s possible they are cold hardy. One accession was 10 feet high, taller than anything typically stated in the literature. The trip offered great insight into the nature of the species but left us frustrated with little to no hope of bringing these plants to the states.

Flora of China consolidates H. angustipetala under H. chinensis, describing the latter as a common and widespread taxon that forms a species complex from which a number of segregate species have been recognized. It occurs in sparse to dense forests on mountain slopes, mountain tops and in valleys up to 6,600 feet elevation.

GRIN (Germplasm Resources Information Network) does not list H. angustipetala, but legitimizes H. chinensis. The RHS Plant Finder 2018 lists the species as H. scandens subsp. chinensis f. angustipetala. Who/what to believe?

Hydrangea angustipetala (99116) has been available in the U.S. via Dan Hinkley’s collection efforts, and other clones have surfaced. His original accession is still in my possession and green as grass after 22.7°F on Dec. 6, 2018.

The ‘Lady in Red’ (extremely hardy H. macrophylla × H. serrata introduction) × H. angustipetala selection named ‘Irish Lace’ is evergreen and as cold hardy as the Hinkley accession. The foliage of the hybrid is similar to H. angustipetala but the sepals are streaked and mottled with green. The foliage of every H. macrophylla and H. serrata was killed at this temperature. Unfortunately, the pom-pom stemmed hybrid did not materialize as the breeding only proceed to the F1 generation and, with two lacecaps as parents, it was an impossibility. To achieve the brussel sprout goal, ‘Irish Lace’ or the Hinkley H. angustipetala should be crossed with mophead H. macrophylla. See “Production and verification of Hydrangea macrophylla x H. angustipetala hybrids” HortScience 44 (6): 1534-1537. 2009 for full details.

Recently, my interest in H. angustipetala was rekindled with the introduction of Runaway Bride ‘Snow White’, which appears to have H. angustipetala as one parent. In The Plantsman New Series 17 part 3: 184-185 (2018), it is described as “Runaway Bride Snow White develops a graceful weeping habit, 4 feet by 4 feet, white lacecap flowers are borne along the length of the shoot, continuing later in the season. Bred by Ushio Sakazaki, Osaka, Japan, this is the prototype for a completely new category of hydrangea.” It was awarded the prestigious Plant of the Year at the 2018 Chelsea Flower Show and was introduced by Thompson and Morgan in the U.K.

In our University of Georgia breeding, we were so focused on developing remontant/reblooming mophead H. macrophylla that we did not envision a future for a more refined, elegant hydrangea. Although Runaway Bride is a lacecap, I surmise breeders are at the work bench developing mophead and/or larger lacecap types with pink-rose-red sepals. Tunnel vision can be both positive or negative in a breeding program. The fact another breeder succeeded with our original premise suggests we may have been ahead of the market. NM