Leaf tissue nutrient sufficiency ranges of four Heuchera cultivars by chronological age

Coral bells (Heuchera sp.) are popular herbaceous perennials grown for their colorful foliage and venation and their aesthetic appeal in mixed containers and landscapes. Commercial coral bell production requires greenhouse or nursery growers to optimize production inputs such as managing mineral nutrition, thereby maximizing plant growth potential and foliage color. The objective of this study was 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. Coral bells (H. hybrida ‘Black Beauty’, ‘Cherry Cola’, ‘Marmalade’, and ‘Peppermint Spice’), varying in leaf color, were grown under one of six constant liquid fertilizer concentrations [50, 75, 100, 200, 300, or 400 mg_·L^-1 nitrogen (N)] with a constant level of water-soluble micronutrient blend in a greenhouse. Fertilizer concentrations for optimal plant growth and development were determined by analyzing plant height, diameter, growth index, and total dry mass, and were found to be 50 to 75 mg_·L^-1 N after a nine-week crop cycle. Recently mature leaf tissue samples were collected and analyzed for elemental content of 11 nutrients at 3, 6, and 9 weeks after transplant (WAT) from plants fertilized with 50 to 75 mg_·L^-1 N. The black- (‘Black Beauty’) and red- (‘Cherry Cola’) colored-leaved cultivars contained higher total N, phosphorus (P), potassium (K), calcium (Ca), sulfur (S), zinc (Zn), and boron (B) than the orange- (‘Marmalade’) and green-(‘Peppermint Spice’) colored-leaved cultivars. For instance, in mature growth, total N concentration for ‘Black Beauty’ and ‘Cherry Cola’ ranged between 3.45 to 3.63% and 3.92% to 4.18% N, respectively, whereas for ‘Marmalade’ and ‘Peppermint Spice’, ranges were between 2.98% to 3.25% and 2.78% to 3.23% N, respectively. Optimal leaf tissue concentration sufficiency ranges determined in this scientifically based study were narrower and often times higher than previously reported survey values for coral bells.