Underutilized Landscape Plants: Calycanthus (chinensis x occidentalis) 'Aphrodite' and Calycanthus x raulstonii 'Hartlage Wine'

I have always loved Calycanthus floridus, the North American native sweetshrub. But honestly, its flowers, while fascinating, were on the small side and never particularly ornamental. When visiting the Coastal Maine Botanic Garden, I noticed a sizeable shrub with dark green healthy foliage, deep maroon, large spider-like flowers that greeted visitors at the front entrance. It sure looked like a sweetshrub, the twigs smelled like a sweet shrub, but were far more ornamental than any native sweetshrub I have seen.

This shrub is Calycanthus (sinensis x occidentalis) 'Aphrodite'. This hybrid by Dr. Tom Ranney, University of North Carolina, is a cross between Calycanthus sinensis and Calycanthus occidentalis, the western native sweetshrub. The flowers of this cross are said to be fragrant, but I can't say I noticed any fragrance either in Maine or at the Penn State Arboretum, where it can also be found.

These shrubs thrive in part sun (4–6 hours) to full sun (over 6 hours). Sweetshrub will grow quite happily in shade, but will most likely grow taller and rangier, with reduced flowering. Typically, it is a large shrub, the height 8–10 ft with a similar spread as compared to the native's 6–10 ft height. Although it prefers rich loam soils, it cheerfully tolerates a wide range of soil conditions from sandy to clay but is not particularly drought tolerant. As an added bonus, because of the fragrance of the twigs and foliage, deer tend to leave this shrub alone. In my landscape, with a herd of fifteen deer regularly wandering through, this characteristic almost outranks the ornamental value. Most sources list Aphrodite as hardy to zone 5. You can prune to size after bloom.

A similar cross, Calycanthus x raulstonii 'Hartlage Wine' was developed by an undergraduate of North Carolina University, Richard Hartlage. What a coup! Hartlage Wine was the first C. floridus, C. chinensis cross introduced in the trade. The two crosses, Aphrodite and Hartlage Wine, are very similar, but there are subtle differences. One is size. By all accounts, Hartlage Wine is slightly smaller than Aphrodite, though still 6–8 ft. The flowers of Aphrodite are so large, easily the size of your palm, they are often described as magnolia-like. Aphrodite's tepals are slightly wider and possess a pronounced yellow center (the actual petals), really highlighting the dark, rich wine color.

Hartlage Wine is also beautiful, but not quite as large or striking. Dirr reports that in Georgia, Hartlage Wine starts blooming in late April for about 4 weeks, while Aphrodite usually starts a few weeks later. When I visited the Penn State Arboretum in May 2021, the Hartlage Wine plants were blooming strongly (see Figure 2 below).

Aphrodite reportedly blooms all summer if sited correctly. I can attest that when I visited the Coastal Maine Botanic Gardens in late July, it was covered in blooms. (See picture). One possible concern with Aphrodite, even though it is listed as a sterile hybrid I have seen seedpods on one shrub. I have not detected fragrance from either cross but the fragrance is often dependent on the nose sniffing the flower. I do recommend if a fragrance is important that you wait till the specimen is blooming and determine for yourself if the fragrance is detectable. As far as fall color, I have seen the Aphrodite fall foliage, a golden yellow. I have not seen Hartlage Wine and can't verify what color the foliage develops.

How to use these beautiful shrubs in the landscape? Why not enliven a privacy screen with the blooms, deer resistance, and tolerance of the sweetshrub crosses? It is a lovely addition to an understory planting, shrub border, or even native landscape. I like the serendipity of locating this shrub at a curve in a path as a pleasant surprise along the journey. Its flowers encourage the wanderer to stop and examine their unusual appearance, while the shrub size hides the rest of the path from view. Or you could locate it as a backdrop to a bench to encourage the viewer to stop, rest, enjoy the blooms, and see if they can detect the fragrance.

I don't want to discourage the use of the native Carolina allspice, Calycanthus florida. It is an interesting plant, with many more named options now, and I will sometimes mix it in with the more ornamental Aphrodite and Hartlage Wine. As landscape designers, we sometimes select the plant that best provides interest, diversity, tolerates the site conditions, and meets our client's sense of aesthetic. It is all a balancing act and combining the two types of sweetshrub may be the answer you are looking for.

Sources

Get sweet on sweetshrub. Michael A. Dirr, January 18, 2019

Missouri Botanical Garden