'Harbour Dwarf' nandina is a noninvasive selection of the invasive ornamental, Nandina domestica, as determined by the UF/IFAS Infraspecific Taxon Protocol*, a tool used to evaluate invasiveness of cultivars and varieties. 'Harbour Dwarf', a dwarf form of nandina, is a low-growing evergreen shrub characterized by short, upright, cane-like stems that grow from a "crown" of basal buds at the soil surface (Gilman 2007; Figure 1).
Growth is dense and compact, resulting in the overall effect of a mounded plant form. Unlike most other cultivars, 'Harbour Dwarf' has 2–4 in. rhizomes that can slowly grow outward from the "crown" and form new stems. This rhizomatous growth increases plant density and width, making 'Harbour Dwarf' especially effective as a shrubby groundcover.
'Harbour Dwarf' differs from the species type of Nandina domestica in being distinctly compact and significantly shorter, and in having leaves that are larger, longer, and lacier in appearance. University of Florida research in north and south Florida showed that 'Harbour Dwarf' nandina produced flowers in April and May in both locations, but fruit only formed in north Florida (Knox and Wilson 2006). The number of fruits formed in north Florida was 97% less than on the species type.
*Nandina domestica cv. Harbour Dwarf ('Harbour Dwarf' nandina) has been evaluated using the Infraspecific Taxon Protocol https://edis.ifas.ufl.edu/ag376 that is associated with the IFAS Assessment of Non-Native Plants in Florida's Natural Areas (UF/IFAS Assessment 2016). Based on evaluation through the protocol, the conclusion for N. domestica 'Harbour Dwarf' is that this is not a problem cultivar in South Florida and may be used there; furthermore, 'Harbour Dwarf' may be recommended with caution for use in central and north Florida, where it should be managed to prevent escape.
'Harbour Dwarf' appears very dense because leaves are closely spaced on the stems. The dark green leaves are double pinnately compound, giving individual leaves an airy and lacy appearance (Figure 2).
Low temperatures in fall and winter turn the outer leaves of 'Harbour Dwarf' nandina burgundy (Figure 3).
This coloration often persists until new growth flushes in spring.
'Harbour Dwarf' plants consistently received high visual quality ratings in a two-year University of Florida evaluation of nandina cultivars in north and south Florida (Knox and Wilson 2006). As a dwarf form of nandina, it often remains no more than 18 in. tall for many years before eventually reaching a height of 32 in. Plants grown in north and south Florida for two years had a mean height of 8 in. and widths from 9 to 12 in. Plants grown in a north Florida landscape for nine years ranged in height from 24 to 32 in. and were up to twice as wide as they were tall.
'Harbour Dwarf' nandina is widely planted in masses as a shrubby groundcover (Figure 4).
In addition, it may be used as an accent plant or in borders and foundation plantings. Its primary ornamental features are its finely textured foliage and compact form. As one of the most popular nandina selections, 'Harbour Dwarf' is commonly used in north Florida, less often used in central Florida, and rarely used in south Florida landscapes.
'Harbour Dwarf' nandina grows best in moist, fertile soil under light shade. It tends not to persist in full sun or dry soils unless mulched and irrigated regularly. 'Harbour Dwarf' nandina is otherwise tolerant of most soil types. Furthermore, it is considered pest free and does not require pruning. As with the standard species type, 'Harbour Dwarf' nandina is hardy within USDA hardiness zones 6–10.
'Harbour Dwarf' plants may form berries 8–16 weeks after flowering. Most fruits fall before maturing, but small numbers may persist, maturing to a red color in winter (Figure 5). The red berries should be removed to prevent wildlife from feeding on the fruit and spreading seeds to natural areas. 'Harbour Dwarf' nandina is commercially propagated by division, cuttings, or tissue culture; it does not come "true" from seed.
This plant was discovered in 1956 by W. C. Lowe at the site of a former nursery near Colfax, North Carolina (Meyer 1979). He noticed the dwarf plant in a group of seed-grown nandinas originally planted by the deceased nursery owner, C. L. Harbour. Lowe recognized the plant's novelty and value and purchased the dwarf nandina from the new property owner, naming it 'Harbour Dwarf'. Widespread promotion of 'Harbour Dwarf' nandina began in 1961 after purchase and use of the dwarf nandina by Fred C. Galle, director of horticulture at Callaway Gardens, Pine Mountain, Georgia. The first nursery listing of 'Harbour Dwarf' nandina was in the 1977 catalog of Monrovia Nursery, Azusa, California. Within the last decade, it has been approved (UF/IFAS Assessment 2016) and promoted (Knox and Wilson 2006) as a non-invasive cultivar in Florida and used as a reference for developing new sterile forms (Deng et al. 2011).
For More Information
Deng, Z., S. M. Smith, G. W. Knox, and S. B. Wilson. 2011. Induction and characterization of tetraploids in nandina. HortScience 46(9):S169. https://ashs.confex.com/ashs/2011/webprogram/Paper5444.html
Dirr, M. 2002. Dirr's trees and shrubs for warm climates: An illustrated encyclopedia. Portland, OR: Timber Press.
Gilman, E. F. 1999. Nandina domestica 'Harbour Dwarf' Harbour Dwarf nandina. FP422. Gainesville: University of Florida Institute of Food and Agricultural Sciences. https://edis.ifas.ufl.edu/fp422.
UF/IFAS Assessment. 2016. UF/IFAS assessment of non-native plants in Florida's natural areas. http://assessment.ifas.ufl.edu/ Center for Aquatic and Invasive Plants (accessed June 26, 2016).
Knox, G. W., and S. B. Wilson. 2006. Evaluating North and South Florida landscape performance and fruiting of ten cultivars and a wild-type selection of Nandina domestica, a potentially invasive shrub. Journal of Environmental Horticulture 24:137–142.
Langeland, K. A., and K. Craddock Burks. 1998. Identification and biology of non-native plants in Florida's natural areas. Gainesville: University of Florida Institute of Food and Agricultural Sciences.
Meyer, F. G. 1979. New and noteworthy woody plant cultivars. The Bulletin of the American Association of Botanic Gardens and Arboreta 13:85–87.
Roethling, J. L., C. T. Glenn, and F. T. Lasseigne. 2003. Long-term evaluation of Nandina domestica cultivars at the JC Raulston Arboretum. Proceedings of the Southern Nursery Association Research Conference 48:373–378.