There is increased interest among ornamental plant growers to identify native shrubs that can be produced commercially for the nursery and landscape industry. Native shrubs must propagate readily from stem cuttings because this method yields uniform plants. In addition, plants must grow well in containers to become a successful commercial crop. Three eastern U.S. native deciduous shrubs with ornamental potential for landscape use are american fly honeysuckle, hobblebush, and sweetbells.
American fly honeysuckle is native from New Brunswick to Manitoba in Canada, and south to Connecticut, Pennsylvania, and Michigan (Hightshoe, 1988). Plants have a multistemmed low-mounded habit, grow 2 to 5 ft in height, and have lime green summer foliage. Plants are especially useful for their early spring tubular yellow flowers and adaptability to dry, shaded locations. Stem cuttings taken from May to June and treated with 3000 ppm IBA root at 49% (Cartabiano and Lubell, 2013). Small liner plants require lower fertility levels than established containers of trade #1 size or larger (Lubell and Shrestha, 2016).
Hobblebush is native from New Brunswick to Ontario in Canada, and south to Connecticut, northern Pennsylvania, and the mountains of North Carolina (Hightshoe, 1988). Plants grow 6 to 12 ft in height, are rhizomatous, and sucker to produce a loose colony of stems with tiered branching. The large, 3 to 5-inch diameter, heart-shaped leaves are medium to dark green in summer and transition to deep red in fall (Dirr, 2009). This shrub is highly sought after for its robust foliage and large (3 to 5-inch diameter), white, lace-cap inflorescences, but supplies of the plant are constrained by a myriad of propagation difficulties (Dirr and Heuser, 1987).
The native range of sweetbells begins in southern Massachusetts and extends south along the U.S. Atlantic coast and then west to Louisiana (Dirr, 2009). Plants have an upright, multistemmed, suckering habit and grow 4 to 6 ft in height. Leaves emerge with a reddish cast before turning bright green in summer and then often a vibrant, scarlet red in fall. They are small, white, urn-shaped flowers that produce a slight fragrance and are held on 2 to 4-inch-long, one-sided terminal racemes. Sweetbells has proven to be highly adaptable to dry and exposed landscape conditions and exhibits a high level of white-tailed deer (Odocoileus virginianus) resistance (Shrestha and Lubell, 2015).
There are no published reports about softwood stem-cutting propagation of hobblebush and sweetbells; therefore, we evaluated the impact of increasing concentration of rooting hormone on softwood stem cutting success for these two native species. Because american fly honeysuckle, hobblebush, and sweetbells are primarily considered to be understory shrubs (Dirr, 2009), an additional objective of this study was to evaluate plant growth and performance in containers under increasing levels of shade. Shading during production may improve foliar coloration and maintain a cooler root zone, which is beneficial for plant growth and appearance (Brand, 1997). Other studies looking at plants that naturally grow in shade such as golden hakone grass (Hakonechloa macra ‘Aureola’) and mountain laurel (Kalmia latifolia) have shown benefits of using shade in production (Brand, 1997; Harvey and Brand, 2002). Growers typically use shade of 30% to 40% and 60% to 70% depending on the crops they are growing and the geographic location of production.
Brand, M.H. 1997 Shade influences plant growth, leaf color, and chlorophyll content of Kalmia latifolia L. cultivars HortScience 32 206 208
Dirr, M.A. 2009 Manual of woody landscape plants. 6th ed. Stipes Publ., Champaign, IL
Dirr, M.A. & Heuser, C.W. 1987 The reference manual of woody plant propagation. Varsity Press, Athens, GA
Durhman, A.K., Rowe, D.B. & Rugh, C.L. 2006 Effect of watering regimen on chlorophyll fluorescence and growth of selected green roof plant taxa HortScience 41 1623 1628
Eksi, M., Rowe, D.B., Fernandez-Canero, R. & Cregg, B.M. 2015 Effect of substrate compost percentage on green roof vegetable production Urban For. Urban Green. 14 315 322
Fisker, S., Rose, R. & Haase, D.L. 1995 Chlorophyll fluorescence as a measure of cold hardiness and freezing stress in 1+1 douglas-fir seedlings For. Sci. 41 564 575
Genoud, C., Coudret, A., Amalric, C. & Sallanon, H. 1999 Effects of micropropagation conditions of rose shootlets on chlorophyll fluorescence Photosynthetica 36 243 251
Harvey, M.P. & Brand, M.H. 2002 Division size and shade density influence growth and container production of Hakonechloa macra Makino ‘Aureola’ HortScience 37 196 199
Hightshoe, G.L. 1988 Native trees, shrubs and vines for urban and rural America. Wiley, New York, NY
Kraus, G.H. & Weis, E. 1991 Chlorophyll fluorescence and photosynthesis: The basics Annu. Rev. Plant Physiol. Plant Mol. Biol. 42 313 349
Lehrer, J.M. & Brand, M.H. 2010 Purple-leaved Japanese barberry (var. atropurpurea) genotypes become visually indistinguishable from green-leaved genotypes (Berberis thunbergii) at low light levels J. Environ. Hort. 28 187 189
Lubell, J.D. 2013 Softwood cutting propagation of northeast United States native shrub species Proc. Intl. Plant Prop. Soc. 63 275 276
Lubell, J.D. & Shrestha, P. 2016 Optimizing container production of American fly honeysuckle (Lonicera canadensis), beaked filbert (Corylus cornuta), and maple leaf viburnum (Viburnum acerifolium) Native Plants J. 17 39 45
Markham, J.W. 2010 Color and shading of containers affects root-zone temperatures and growth of nursery plants. Kansas State Univ., Manhattan, MS Thesis
Mathers, H.M. 2003 Summary of temperature stress issues in nursery containers and current methods of protection HortTechnology 13 617 624
Shrestha, P. & Lubell, J.D. 2015 Suitability of eight northeasetern U.S. native shrubs as replacements for invasive plants in a difficult landscape with white-tailed deer pressure HortTechnology 25 171 176