Article and photos (except where noted) by Katherine Wagner-Reiss

2003-062 Spiraea thunbergii ‘Ogon’ in bloom. Photo courtesy of Lucy Dinsmore.

Spiraea thunbergii ‘Ogon’ is a delightful early spring-blooming shrub in the rose family; come see it at the Morris Arboretum, and, since it is widely available at nurseries, you can consider it for your own garden. Spiraea comes from the Greek word speira meaning spiral or twisted: the flexible stems of spirea can be twisted into garlands and wreaths. The specific epithet thunbergii honors Carl Peter Thunberg (1743–1828), the Swedish physician who introduced this species to Europe and who named over 250 plant and animal species. He was one of Linnaeus’s so-called “apostles:” 17 men who travelled the world to send him natural specimens (and he is certainly one of the lucky ones, since seven did not return home alive). The first leg of his adventure was a successful three-year collecting stint in the Dutch Cape Colony in southern Africa, where he also learned to speak Dutch, essential knowledge for entry into his next stop, Japan. Offput by the zeal of European missionaries in the 1600s, Japan was closed to most foreigners, allowing only two Dutch East India Trade ships to enter the port of Nagasaki each year; Thunberg was able to pass as Dutch when he arrived as ship’s surgeon on one such boat in 1775. The travel, even of the Dutch, was restricted to a small island in the harbor. Thunberg got away with a few explorations around Nagasaki, and he was able to collect some plants as he accompanied the Dutch ambassador who visited the Shogun in Tokyo, but his main source of plant material was Japanese interpreters; some of these were physicians anxious to learn about Western medicine, including mercury treatment for syphilis. This naturalist is honored with a plant genus name, Thunbergia, and many specific epithets e.g. Allium thunbergii, Berberis thunbergii, Geranium thunbergii, and Pinus thunbergiana.

Thunbergia grandiflora in FL 

Thunbergia alata in FL

Thunbergia erecta in FL


2006-067*A Spiraea thunbergii ‘Ogon’ (Mellow Yellow Thunberg spirea)  

‘Ogon’ means gold in Japanese, and the willow-like foliage of the cultivar ‘Ogon’ is known for being golden instead of the usual green, especially when grown in full sun. Discovered in a Tokyo plant market by Barry Yinger, a Pennsylvania plantsman who made over 60 plant-hunting trips to Japan, it was introduced into the USA in 1993, and is now more popular than the green-leaved parent species whose common name is baby’s breath spirea. The trade name for “Ogon’ is MELLOW YELLOW Thunberg spirea. It is difficult to track down the origins of cultivar names, but a possible guess is that this one might have been inspired by the popular song “Mellow Yellow,” written and recorded by Scottish singer-songwriter Donovan in the 1960s.

How do you pronounce Spiraea thunbergii ‘Ogon’? Spiraea is pronounced spy-REE-ah; the common name, spirea, drops that silent “a,” making the pronunciation more straightforward. As far as thunbergii, the general convention is that a proper name be pronounced the way that the honoree pronounces or pronounced his/her own name; thus, Toon-BERG- ee- eye would seem to be the most authentic choice, although you will hear reputable sources pronouncing it as Thun-BERG-ee-eye and even Thun- BERJ-ee-eye. And finally, how is ‘Ogon’ pronounced? Since 1/1/1959, new cultivar names are given not in botanical Latin, but in the vernacular. ‘Ogon’ rhymes with shogun to my ear, but to hear the authentic pronunciation you need a Japanese speaker.黄金

Come see this shrub and many other species of Spiraea blooming at the Morris Arboretum this April, including three species native to the US: S. betulifolia ‘Tor’ from western NA, S. latifolia from eastern NA, and S. virginiana from southeastern US. A particularly historic specimen remains from the time of the Morris estate: Spiraea x vanhouttei, which you may know as good old-fashioned bridalwreath. If you are interested in seeing another plant named for C. P. Thunberg, there are three Pinus thunbergiana at the Morris Arboretum. Find exact locations of any of these plants at Collection Connection.

1986-079*G Pinus thunbergiana—new spring growth (candles), male and female cones

Berberis thunbergii ‘Rose Glow’. You won’t find this barberry at the Morris Arboretum: B. thunbergii is a Class 1 invasive species in Pennsylvania, although some cultivars produce less seed than the species.