Re-inventing Sweetshrubs
Dr. Thomas G. Ranney

The sweetshrubs (Calycanthus/Sinocalycanthus) are among the oldest known flowering plants with fossil records dating back to the early and mid cretaceous periods (144 – 65 million years ago). As the Age of Dinosaurs came to an end, and the supercontinent Pangea was rifting apart, these ancient plants were present and on the move, radiating out around the world.
Although the sweetshrubs are not generally considered mainstream landscape plants, they hold great promise. The sweetshubs offer fragrant flowers, attractive foliage, broad adaptability, shade tolerance, and excellent pest resistance. Once discovered, gardeners invariably become infatuated and muse romantically about the alluring fragrance and subtle charm of sweetshrubs. No garden should be without them!
The family Calycanthaceae is small and includes 3-4 genera including Chimonanthus (Asia), Calycanthus (North America), Sinocalycanthus (Asia) and Idiospermum (Austrailia). There are two species of sweetshrubs native to North America, the Carolina sweetshrub (Calycanthus floridus) and the California sweetshrub (Calycanthus occidentalis). The Chinese wax shrub (Sinocalycanthus chinensis) is a rare species native to the Zheijang Province in southeast China and is more closely related to the Calycanthus than are the other two genera.
The Carolina sweetshrub is naturally found throughout much the Eastern United States and commonly grows as an understory shrub in mixed deciduous forests, often along streams and in moist woodlands. The leaves and stems are strongly aromatic and the bark, at one time, was used as a substitute for cinnamon. Height can vary and ranges from 3 to 9 feet, growing as multi-stemmed shrubs with suckering shoots arising from the base and roots. Fall color can be an attractive buttery yellow. The flowers, however, are the main attraction. Although they may not be considered show-stoppers from a distance, the primitive upright flowers are packed with tepals that vary from reddish purple to a dark chocolate brown. The fragrance is also variable and somewhat hard to describe. Wine connoisseurs could have a heyday describing the complex aromas of strawberries and melons with subtle accents of cinnamon and spices. Others simply inhale and go ahhhhh!
The California sweetshrub is naturally found in Washington and California growing as an understory species along streams and on moist canyon slopes. Although similar to the Carolina sweetshrub, the California species is larger in most all respects with the plants growing to over 12’ tall. The flowers, though larger and a brighter red, are typically not as fragrant.
Chinese wax shrub was only recently introduced into cultivation after being distributed by the Shanghai Botanical Garden in 1980. This medium-sized shrub grows to 3 to 9 feet tall with large, glossy leaves. The flowers open more completely than do Calycanthus spp. and are multicolored with the outer perianth whorl being whitish pink and the inner whorl being a strong yellow with occasional purple streaks at the base. Unfortunately, there is little fragrance. Despite its fairly southern origins, the Chinese wax shrub has proven hardy in USDA zone 5.
The Chinese wax shrub is closely related to our North American sweetshrubs. In paleobotany terms, many closely related taxa that are found in both North America and Asia, are referred to as "disjunct Tertiary relics". After Pangia fractured, with Laurasia going to the Northern Hemisphere and Gondwana moving to the Southern, Laurasia broke apart in the Tertiary period (26-66 million years ago). This disjunction separated North America from Eurasia and separated the population of plants that eventually gave rise to Calycanthus and Sinocalycanthus. Similar patterns exist for the Magnolia, Liriodendron, Cotinus, and Hamamelis.
A quick breakdown of species, varieties, and cultivars:
Calycanthus floridus (sweetshrub, strawberry-shrub, Carolina allspice, Carolina sweetshrub, spicebush). Distinguished by obovate-lanceolate to oblong-elliptic tepals, 10-20 stamens, and lateral bud partially hidden by the petiole base. There are two varieties that vary primarily in the degree of pubescence on the leaves and twigs. However, the ranges of these varieties overlap and variation in the amount of pubescence is common.
Calycanthus floridus var. floridus (Calycanthus brockianus, C. mohrii). Twigs, petiole, and abaxial surface of leaf pubescent.
Calycanthus floridus var. glaucus (Calycanthus glaucus, C. fertilis, C. floridus var. laevigatus, C. floridus var. oblongifolius, C. nanus). Twigs, petiole, and abaxial surface of leaf glabrous or with scattered trichomes.
Notable cultivars:
‘Athens’ – One of a number of yellow/green flowered forms with lustrous, dark green foliage, and excellent flower fragrance. A number of other yellow flowered, but unnamed, forms exist. Richard Weaver, formally with We-Du Nurseries, and Wyatt LeFever, with Blue Ridge Fish Hatchery, have both discovered additional yellow forms in the wilds of North Carolina. Interestingly, these yellow flowered forms were once considered to be a separate species, C. brochianus, but this treatment is generally no longer accepted.
‘Michel Lindsey’ – Introduced by Holbrook Farm and Nursery, formally in Fletcher, NC. Extremely lustrous, glossy foliage with very fragrant reddish brown flowers and yellow fall color.
‘Purpureus’ – Grown mostly in Europe. Somewhat disappointing with the underside of the leaves being only slightly purple – a trait that can be found in seedling populations of C. floridus.
Calycanthus occidentalis (California spicebush, California sweetshrub). Distinguished by linear to linear-spatulate to ovate-elliptic tepals, 10-15 stamens, and lateral buds being exposed.
Sinocalycanthus chinensis (Calycanthus chinensis) (Chinese wax shrub). Distinguished by the large leaves 16-25 cm long and 10-12 cm wide, tepals arranged in two distinct series, and whitish pink flower color with yellow inner tepals.
The New Sweetshrubs.
As reported by Lasseigne et al. (2001), Richard Hartlage, then an undergraduate student in Horticultural Science at North Carolina State Univ., performed reciprocal crosses between Sinocalycanthus chinensis and Calycanthus floridus in 1991. Four seedlings resulted, one of which appeared to be a hybrid and it bloomed 5 years later. This hybrid was later named _Sinocalycalycanthus raulstonii Lasseigne and Fantz ‘Hartlage Wine’.
In many regards, this hybrid retains the best qualities of both parents with large, maroon, wine-red flowers that open widely with a subtle fragrance and roots easily from cuttings. Once established, plants can be very floriferous and extremely showy.

_Sinocalycanthus raulstonii ‘Hartlage Wine’

Encouraged and inspired by the success of ‘Hartlage Wine’, we have been working on further developing new hybrids of Calycanthus. We have successfully developed additional hybrids between Sincalycanthus chinensis and Calycanthus floridus and new hybrids between Sincalycanthus chinensis and Calycanthus occidentalis. Although most of these hybrids are extremely infertile, we have been able to produce a limited number of advanced generation hybrids that include all three taxa. Many of these hybrids are just now blooming for the first time and the range of characteristics and the potential for new nursery crops is outstanding. We plan to introduce an exceptional new hybrid later this year named ‘Venus’.
‘Venus’ Sweetshrub
(_Sinocalycalycanthus ‘Venus’) PPAF
‘Venus’ is a complex hybrid, developed at NC State University, that includes Sinocalycanthus chinensis, Calycanthus floridus, and Calycanthus occidentalis in its pedigree. The result is exceptional. This medium-sized shrub produces large, ivory yellow buds that transform into large, magnolia-like, white flowers with yellow and purple infusions in the center. The flowers have an enticing fragrance with aromas of strawberries and melons. Flowering is primarily in the spring, though additional flowers are produced throughout the growing season. ‘Venus’ is being patented and should be available to propagators by mid-summer.

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