Chinese Sweetshrub (Calycanthus chinensis)

Pollinated only by small beetles, the chinese sweetshrub is an attractive specimen plant with showy flowers often seen in foundation plantings and shrub borders. Sadly, it has become rare in its native habitat alongside mountainous streams.

I. Appearance and Characteristics 

Calycanthus chinensis, known as Chinese sweetshrub, is a species of flowering plant in the family Calycanthaceae, native to Southeast China. It was first given a valid scientific name in 1964. It is cultivated as an ornamental flowering shrub, and has been hybridized with two other species in the genus Calycanthus to combine its larger and broader tepalled flowers with their scented and more colourful ones.

It has been treated as the only species in the genus Sinocalycanthus.

Calycanthus chinensis is a deciduous shrub or small tree up to 3 m (10 ft) high and the same across. Older twigs are hairless and have grayish or grayish-brown bark. The leaves are aromatic and arranged in an opposite fashion. The leaf petiole (stalk) is about 12–18 mm (0.5–0.7 in) long. The leaf blade is variable in shape but broadly ovate, 11–18 cm (4.3–7.1 in) long by 8–15 cm (3.1–5.9 in) wide. The base of the leaf petiole hides the lateral buds.

In its original habitat in China, it flowers in May. The nodding flowers are terminal, about 4.5–10 cm (1.8–3.9 in) across, and borne singly on a short pedicel 20–45 mm (0.8–1.8 in) long. There is no clear distinction into sepals and petals. There are about 10–14 white outer tepals, often flushed pink, especially as they age, and about 7–16 yellowish inner tepals, with purple marks near the base. The inner sepals are shorter and thicker than the outer ones, and curve inwards. The fruit matures in October in the wild. It is ovoid, with a spiral of marks at the top showing the former position of the tepals. The seeds are achenes, about 10–12 mm (0.4–0.5 in) long, and have silky hairs.

Calycanthus chinensis has a somewhat confused taxonomic history. It was first described in 1963 as Calycanthus chinensis by W.C. Cheng and S.Y. Chang. However, their use of the name was invalid under the International Code of Nomenclature for algae, fungi, and plants, because two different collections were both given as holotypes. (Article 9.1 requires the holotype to be only one specimen.) The authors then described it validly in 1964 in their new genus Sinocalycanthus. In 1979, P.T. Li rejected the genus Sinocalycanthus, and validated the original name Calycanthus chinensis (inadvertently according to the International Plant Names Index).

A 2006 molecular phylogenetic study of the family Calycanthaceae found that the three widely recognized species of Calycanthus formed a monophyletic group. Relationships among the three species differed depending on whether chloroplast or nuclear data was used: C. chinensis was either sister to C. floridus plus C. occidentalis, or formed a clade with C. occidentalis, C. floridus being sister to both.

Calycanthus chinensis is cultivated as an ornamental shrub. In the United States, it is usually considered hardy in zones 6–8. In Europe, it is hardy as far north as eastern Scotland. Well-drained but moist, acid soils are recommended. In cooler climates, full sun is recommended, and it will have a long flowering season, beginning in June in southern England. In warmer climates in the US, it will grow in some shade and has a shorter but earlier flowering season, beginning in April. It can be propagated by softwood cuttings in summer, or by seed.

II. How to Grow and Care

Sunlight

Chinese sweetshrub demands full sun to partial shade for optimal flowering.

Watering

Thriving in its native humid environments, chinese sweetshrub has adapted to maintain a consistent moisture level within its tissues. This species exhibits a preference for evenly moist soil and demonstrates moderate drought tolerance once established. Watering should adhere to a schedule of every week to support its hydration needs without over-saturating the roots. Cultivated primarily outdoors, chinese sweetshrub benefits from mulching to retain soil moisture, particularly during its active growing season when water demand is heightened.

Soil

It thrives in well-drained soil with regular watering, but it is drought-tolerant once established. It

Fertilizing

Fertilize chinese sweetshrub in spring with balanced nutrition fertilizers to boost growth and flower development. Apply monthly until late summer, keeping doses moderate to avoid root burn. Fertilization enhances chinese sweetshrub’s vigor, ensuring lush foliage and vibrant blooms. Seasonal adjustments are key–reduce frequency after flowering. Always water chinese sweetshrub thoroughly post-fertilization for nutrient absorption and to prevent chemical concentration. For effective results, follow product instructions closely, considering chinese sweetshrub’s size and soil fertility.

Pruning

Pruning after flowering to maintain shape and encourage bushier growth.

Propagation

Chinese sweetshrub, a member of the Calycanthaceae family, thrives when propagated through cuttings. For successful cultivation, use semi-hardwood cuttings from healthy, disease-free plant material. Make sure to cut just below a set of leaves for optimal rooting potential. It’s imperative to maintain high humidity levels and stable temperatures to encourage root development for chinese sweetshrub. After cutting, apply a rooting hormone to enhance root growth. Plant the cuttings in a well-drained medium and keep the soil consistently moist without being waterlogged.

Transplanting

The perfect moment to relocate a chinese sweetshrub is during S1-S3, as this window aids in its root system’s recovery. It thrives in regions with abundant sunlight and well-draining soil. A tip to remember is to water it generously post-transplant for optimal growth.

Repotting

For chinese sweetshrub, a bushy plant reaching impressive sizes, repotting every 2-3 years promotes health and expansion. Spring is optimal, aligning with its growth cycle. Choose a pot that accommodates its robustness, one size larger than its current. Provide well-draining soil and ensure post-repotting care includes adequate moisture and partial sun exposure to encourage recovery and vigor.

III. Uses and Benefits 

Chinese sweetshrub is perfect as a specimen plant or in shrub borders, foundation plantings, woodlands.