How to Plant, Grow, and Care for Calycanthus (Sweetshrub)

Calycanthus is a valuable U.S. native shrub with unique blooms – both in form and fragrance – and fresh, full foliage. Attractive as a large specimen or in a mixed planting, the adaptable grower is also vigorous and spans climate zones and conditions.

With effortless ornamental appeal, sweetshrub is something we should incorporate more in our displays. Whether the straight species or one of its noteworthy cultivars, you may have just the spot for these durable, beautiful, fast-growing shrubs.

What is Calycanthus?

Commonly called sweetshrub or Carolina allspice, Calycanthus is a U.S. native shrub with a robust, easy-care nature. Scarlet-mahogany blooms dot stems with lustrous, broad leaves in late spring. 

The straight species is valuable and attractive in itself, and award-winning cultivars and hybrids boast improved blooming and fragrance. The underutilized shrubs are worthy of a spot in the garden – if you’ve got the growing room – with versatile applications.

Calycanthus makes an excellent specimen for mass planting in woodland plantings, rear borders, pollinator gardens, and naturalistic arrangements. Place them near entrances, patios, and walkways to enjoy the fragrance. Their size and vigor make exceptional foundation, screen, and privacy hedges. They’re also good additions to sensory and cottage gardens. They make lovely cut flower arrangements, too.

Sweetshrub is valuable to pollinators for nectar and to wildlife as a food source, shelter, and nesting habitat. They’re also fire-resistant. The low-maintenance, easy grower is free of severe pest and disease problems and is not usually bothered by deer.

Characteristics

Sweetshrub has fragrant, chocolate-red blooms that appear in May on short, leafy stems. The two-inch saucers hold strappy petals (actually tepals, where sepals fuse with petals). The buds emerge before the leaves, with continued flowering after the leaves emerge. 

Flower fragrance contains sweet, fruity notes with hints of strawberry, pineapple, and banana, depending on the beholder. Seed capsules follow the blooms and mature in the fall. They last into winter for continued interest.

The shrubs are attractive even when not in flower with handsome foliage, lustrous and deep green with lighter undersides. Leaves turn bright gold in the fall. Both foliage and stems have a spicy, ginny scent when crushed, cut, or bruised.

Carolina allspice has a dense, upright, rounded habit nearly as wide as it is tall. It spreads through suckers and seeds and forms colonies in the wild, though more behaved in the home garden. Buds set on old and new wood for an extended bloom show.

Native Area

C. floridus occurs naturally from Virginia to Florida and performs well outside its native area, with a range from Massachusetts to the mid-west. It withstands cold and hot climates and grows naturally in shady woodlands as an understory shrub and along stream banks. 

There’s a Western species, C. occidentalis, that grows more wildly at up to 12 feet. Its flowers are similar in strappy tepals but more red. This species isn’t as widespread in cultivation.

An Asian species, C. chinensis, is robust with coarser foliage and white flowers. It produces long leaves and several feet of growth in a single season, topping out at 10 to 15 feet tall. It occurs naturally in Southeast China in mountain areas and streams at 3,000 feet.

Planting

Something to note when selecting your Calycanthus: fragrance varies widely per plant. You may want to purchase one in flower in late spring to test its aroma and choose one with a more intense perfume (these aren’t overpowering blossoms).

When planting, space plants at least three feet to five feet apart to allow room for mature growth. The specimens grow quickly and benefit from the elbow room.

Transplanting

Fall and spring are the best times for planting. Cool temperatures and seasonal moisture give roots time to establish before winter and summer temperature fluctuations. For the least stress, avoid planting in frozen or waterlogged conditions and extreme heat or dryness.

How to Grow

The carefree, unfussy growers have low maintenance needs. Even so, certain cultural requirements, like regular moisture and well-draining soils, are best for optimal health and flowering.

Light

Sweetshrub grows best in full sun (six or more hours of sunlight daily) to partial shade (four or more hours). The adaptable native also grows in deeper shade. It may be taller, leggier, and less dense in the shade than the sun, with fewer flowers.

In hot climates, provide afternoon shade protection from intense rays to prevent sun scorch.

Water

Carolina allspice grows best with consistent moisture. Once established, it tolerates brief periods of flooding. It also withstands short dry spells but struggles in prolonged drought conditions.

About an inch of water per week is sufficient, with more needed during hot or dry situations. Water the shrubs through frost to prepare them for winter dormancy.

Soil

The durable native tolerates various soil types, including clay, but does best in organically rich loams. It isn’t picky about pH levels, though slightly acidic to neutral is optimal. Average, medium, well-drained soils are prime.

In poor soils like clay and sand, add compost at planting. Compost improves aeration, moisture retention, drainage, and nutrition. Adding a compost layer to the garden bed or container each spring refreshes these benefits for the growing season.

Temperature and Humidity

The deciduous shrubs are heat and humidity-tolerant, given good air circulation and moist but not overly saturated soils. Cold hardy down to USDA zone 4, they benefit from extra mulch and protection from winter winds in the lowest zones. 

Flower fragrance is stronger in higher springtime temperatures and during the warmest times of the day.

Fertilizing

With nutrient-rich, fertile soils, sweetshrub doesn’t require additional fertilizers to thrive. They’ll benefit from fresh compost each spring. If you opt to fertilize in poor soils, apply a balanced, organic, slow-release, granular like 5-5-5 in early spring before new growth emerges.

Maintenance

Calycanthus is so low maintenance you can spend time enjoying it instead of tending to it. Prune immediately after plants finish flowering to manage size or shape. Remove suckers as they pop up at the base if you don’t want the shrub to spread.

Propagation

Carolina allspice propagates most easily by dividing suckers, ground layering, and seeding. The first two are best begun in spring and early summer, while you can pick seeds green or allow them to ripen for a fall collection.

Dividing Suckers

Dvision from suckers is easy when it comes to sweetshrub. Suckers are the whippy offshoots that arise from the plant’s base. Division involves separating them from the mother plant and transplanting them into containers or their new garden location.

Ground Layering

Ground layering is an easy method of propagation that uses existing branching. Choose a low-growing branch and dig a trench beneath it. Scuff a portion of the stem with clean pruners or a blade and lay it in the trench, keeping the leafy end of the branch above ground.

Cover the scuffed section with soil and weigh it down with a stone or brick. Cut the branch from the mother plant after new roots develop on the stem. Transplant in the garden or into a container.

Growing From Seed

Propagation from seed varies and takes patience, as germination can take between weeks and months. Some growers have luck with green seeds, sowing them fresh with germination in a few weeks. Most do best with a fall collection and exposure to cold and moist stratification. Several weeks to three months of refrigeration or overwintering in the garden helps promote sprouting.

Collect seeds as they brown and direct sow them in a prepped garden area, covering them lightly with soil. If not the straight species, seeds don’t necessarily reflect the qualities of the parent variety, but it’s an easy method to try.

Popular Varieties

C. floridus cultivars and hybrids are particularly showy and ornamental, with larger, richer blooms and fragrances to match. The top performers and award-winners bring unique specializations.

‘Michael Lindsey’

A straight species selection and favorite performer, C. floridus ‘Michael Lindsey’ has glossy, pointed, dark green leaves and vivid gold fall color. This one is among the most sun and heat-tolerant.

The Pennsylvania Horticultural Society granted ‘Michael Lindsey’ their Gold Medal Award. It is a gold standard among the group, performing reliably with heavy blooming and adaptability.

‘Hartlage Wine’

Calycanthus x raulstonii ‘Hartlage Wine’ is a hybrid cross from then-student Richard Hartlage working with J.C. Raulston and North Carolina State University. Its parentage is C. floridus and C. chinensis resulting in a tall, dense grower (up to 12 feet or more) with deep scarlet blooms with yellow markings. It carries a light fragrance. 

The blooms are large and compare to a small magnolia. The Royal Horticultural Society deemed ‘Hartlage Wine’ Award of Garden Merit status.

‘Aphrodite’

Dr. Tom Ranney of the University of North Carolina developed this cross of C. chinensis and C. occidentalis for an extended bloom time of two months. Flowers appear a few weeks later in the season.

C. (sinensis x occidentalis) ‘Aphrodite’ has rich red flowers that open not only on the tips of stems but along their length. 

Common Problems

Another beautiful characteristic of sweetshrub is that it’s free of most pests and diseases. Aphids and whiteflies are occasional visitors. Powdery mildew and bacterial crown gall may be fungal problems. The best control is prevention through maintaining optimal cultural requirements.

Pests

The best way to control insects is to spot them early. You’ll likely see the insects themselves or notice their sticky waste, yellowing leaves, or stunted growth.

Aphids are common sap-sucking insects usually treated with non-chemical means. Often, they cause no plant damage, but severe infestations cause curled leaves and stunted growth.

Whiteflies also feed on sap and cause weakness, where leaves yellow and drop. Adult whiteflies are tiny and white, and you’ll notice them fluttering around foliage when disturbed. Adult females lay eggs on leaf undersides, and nymphs hatch to feed on tissues. The adults pierce foliage to feed on sap. 

If you detect insect infestation, spray the plant with a strong stream of water to deter and knock them off the stems. A simple horticultural soap or oil can rid the plant of invasions, but follow label directions, as these also affect beneficial insects. 

Diseases

As with pests, the best disease control is prevention through cultural conditions, mainly by providing adequate moisture and air circulation.

Powdery mildew is one of the most common fungal problems and is a grayish-white dust on leaves, buds, and stems. Spores spread on the wind, through contact with infected plants or tools, or by splashing up from the soil via raindrops and irrigation. The spores begin on the leaves and spread to the stems, depleting energy and nutrition. Leaves turn yellow, distort, and drop during severe infections. 

Handpick and remove the affected leaves when feasible. Throw them away in a garbage bag or burn pile separate from the compost pile.

For more extensive outbreaks, horticultural oils like neem or insecticidal soaps can treat powdery mildew early on, but again, these impact beneficial insects, so be sure to follow application requirements.

Bacterial crown gall is soil-borne and causes warty growth on the base of the stems near the soil level. Galls also appear on branches and stems. They expand and interfere with water and nutrient absorption, sometimes causing stunted growth and decline. There is no practical treatment for crown gall, and it’s best to remove the affected specimen to prevent the spread.

Frequently Asked Questions