In the United States, coral bell (Heuchera hybrida L.) production increased by 167% ($14.4 million USD) from 1997 to 2014 (USDA, 1998, 2015). The increasing consumer demand for this herbaceous perennial is because of their colorful foliage and venation; mounding growth habit; use in mixed combination containers or landscape plantings; use as pollinator plants and cut flowers; and their drought- and deer-resistance. To continue to meet the increasing consumer demand for coral bells, greenhouse and nursery growers must optimize production inputs (Owen, 2019), such as fertilization. Traditionally, commercial mineral nutrition recommendations for the genera Heuchera range from 50 to 250 mg·L−1 nitrogen (N) on a continual basis (Biernbaum and Morrison, 2000; Pilon, 2006) or 150 to 200 mg·L−1 N as needed (Nau, 2011; Pilon, 2006). These fertility recommendations vary greatly, but the goal of any fertilizer regimen for containerized ornamentals is to provide sufficient but not excessive levels of essential nutrients (Scoggins, 2005). The philosophy of this approach is to monitor the inputs to the crop; and as along as the substrate inputs are within the recommended range, e.g., substrate pH and electrical conductivity (EC), it is assumed the fertility requirements of the crop are being met (Krug et al., 2010). This is consistent with Biernbaum and Morrison (2000), who concluded from a multiple species perennial fertility trial that coral bells (Heuchera sanguinea Engelm. ‘Firefly’) grew best at 62 mg·L−1 N provided continuously than 125 or 250 mg·L−1 N, thus warning against excessive fertilization. However, the N concentrations trialed and concentrations recently reported in the literature are considered optimal.
Optimum fertilization requirements (Biernbaum and Morrison, 2000; Scoggins, 2005) and nutritional leaf tissue sufficiency ranges and standards (Biernbaum and Morrison, 2000; Bryson and Mills, 2014) for the genera Heuchera are limited. Bryson and Mills (2014) reported nutritional leaf tissue sufficiency ranges for H. micrantha Douglas ex Lindl. ‘Palace Purple’ and H. sanguinea; but values represent samples collected mostly from specimens planted in mineral soils at botanical gardens and arboretums, thus providing a wide variability of recommended nutrient levels (Owen, 2019). Therefore, these nutritional standards do not accurately represent the nutritional status nor sufficiency ranges of the genera Heuchera grown by commercial greenhouses and nurseries in soilless substrates. Furthermore, little attention has been given to identifying nutrient requirements and nutritional status of container-grown coral bells by chronological age or as plants developed.
For herbaceous perennials, leaf tissue nutrient sufficiency ranges by chronological age have only been reported for perennial hibiscus (Hibiscus hybrid L. ‘Mocha Moon’ and ‘Starry Starry Night’; Owen, 2019). For annual bedding plants, leaf tissue nutrient sufficiency ranges by chronological age have been reported for pot gerbera (Gerbera jamesonii Bolus ex Hook. f. ‘Festival Light Eye Yellow’; Jeong et al., 2009), osteospermum (Osteospermum hybrida L. ‘Lemon Symphony’, ‘Serenity Lavender Dark’, ‘Summertime Red Velvet’, and ‘Tradewinds Purple Bicolor’; Papineau and Krug, 2014), and zonal geranium (Pelargonium ×hortorum L.H. Bailey ‘Tango Dark Red’ and ‘Rocky Mountain Dark Red’; Krug et al., 2010). Determining sufficiency ranges and leaf nutritional standards by chronological age for the genera Heuchera will establish nutrient recommendations that may aid in identifying nutritional deficiencies and/or toxicities (Owen, 2019) and further define fertilizer recommendations. Therefore, the objectives of this study were to determine the optimum fertilizer concentrations, identify leaf tissue nutrient sufficiency ranges by chronological age, and to expand leaf tissue nutrient standards of coral bells grown in soilless substrates during container production.
Biernbaum, J. & Morrison, M.S. 2000 Forcing perennials: Root zone management, p. 13–16. In: Greenhouse Grower Magazine and Michigan State University (eds.). Firing up perennials: The 2000 edition. Meister Media, Willoughby, OH
Bryson, G.M. & Mills, H.A. 2014 Plant analysis handbook IV. Micro-Macro Publishing, Athens, GA
Fonteno, W.C., Harden, C.T. & Brewster, J.P. 1995 Procedures for determining physical properties of horticultural substrates using the NC State University porometer. North Carolina State University, Horticulture Substrates Lab., Raleigh, NC
Jeong, K.Y., Whipker, B., McCall, I. & Frantz, J. 2009 Gerbera leaf tissue nutrient sufficiency ranges by chronological age Acta Hort. 843 183 190
Judkins, W.P. & Wanders. I.W. 1949 Correlation between leaf color, leaf nitrogen content, and growth of apple, peach, and grape plants Plant Physiol. 25 78 85
Krug, B.A., Whipker, B.E., McCall, I. & Cleveland, B. 2010 Geranium leaf tissue nutrient sufficiency ranges by chronological age J. Plant Nutr. 33 339 350
Nau, J. 2011 Heuchera, p. 444–446. In: J. Nau (ed.). Ball redbook. Ball Publishing, Batavia, IL
Perry, L.P. 2011 Coralbells (Heuchera) hardiness research 2010–2011. Univ. of Vermont Sustainable Herbaceous Perennials Research. 11 Mar. 2019. <http://pss.uvm.edu/ppp/coralbells10.11.pdf/>
Pilon, P. 2006 Heuchera, p. 452–456. In: P. Pilon (ed.). Perennial solutions: A grower’s guide to perennial production. Ball Publishing, Batavia, IL
Scoggins, H.L. 2005 Determination of optimum fertilizer concentration and corresponding substrate electrical conductivity for ten taxa of herbaceous perennials HortScience 40 1504 1506
U.S. Department of Agriculture (USDA) 1998 1997 Census of horticultural specialties. National Agricultural Statistics Service, U.S. Department of Agriculture, Washington, D.C. 11 Mar. 2019. <http://usda.mannlib.cornell.edu/usda/AgCensusImages/1997/03/04/1997-03-04.pdf/>
U.S. Department of Agriculture (USDA) 2015 2014 Census of horticultural specialties. National Agricultural Statistics Service, U.S. Department of Agriculture, Washington, D.C. 11 Mar. 2019. <https://www.nass.usda.gov/Publications/AgCensus/2012/Online_Resources/Census_of_Horticulture_Specialties/HORTIC.pdf/>.