Hibiscus Leaf Tissue Nutrient Sufficiency Ranges by Chronological Age

Abstract

Perennial hibiscus (Hibiscus sp.) are popular summer-flowering plants that are grown in greenhouses or nurseries, where growers must optimize production inputs such as fertility to maximize plant growth and produce high-quality flowering crops. 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 Hibiscus hybrid L. (hibiscus) grown in soilless substrates during container production. Two cultivars of hibiscus (H. hybrid L. 'Mocha Moon' and 'Starry Starry Night') were grown under one of six constant liquid fertilizer concentrations [50, 75, 100, 200, 300, or 400 mg · L L1 nitrogen (N)] with a constant level of water-soluble micronutrient blend in a greenhouse. The fertilizer concentrations sufficient for optimal plant growth and development were determined by analyzing plant height, diameter, growth index (GI), primary shoot caliper (PSC), and total dry mass, and they were found to be 100-300 mg · L L1 N after an 8-week crop cycle. Recently, mature leaf tissue samples were collected and analyzed for elemental content of 12 nutrients at 2, 4, 6, and 8 weeks after transplant (WAT) from plants fertilized with 100-300 mg · L L1 N. An overall trend of increasing sufficient tissue concentration over time was observed for total N, phosphorus (P), calcium (Ca), sulfur (S), zinc (Zn), copper (Cu), and boron (B), whereas a decreasing trend was observed for potassium (K), iron (Fe), manganese (Mn), and aluminum (Al). For instance, at 2 WAT, total N ranged from 3.1% to 5.1% N and increased to a range of 4.2% to 4.7% N at 8 WAT. At 2 WAT, Fe and Mn ranged from 79.2 to 103.6 mg · L L1 Fe and 66.3-82.8 mg · L L1 Mn and decreased to ranges of 75.6-82.9 mg · L L1 Fe and 18.1-99.7 mg · L L1 Mn at 8 WAT, respectively. Optimal leaf tissue concentration sufficiency ranges determined in this scientifically-based study were narrower than previously reported survey values for the genera Hibiscus.

Leaf Tissue Nutrient Sufficiency Ranges of Four Heuchera Cultivars by Chronological Age

“…Additionally, average substrate pH decreased by 19% (1.1 pH units), from 5.8 to 4.7 pH units, as fertilizer concentration increased from 50 to 400 mg • L -1 N, respectively. Therefore, based on these results and visual observations, it was concluded that plants fertilized with $100 mg • L -1 N were entering a situation of luxury to detrimental nutrient consumption, and the additional fertilizer was not beneficial to plant quality (Jeong et al, 2009;Krug et al, 2010;Owen, 2019;Papineau and Krug, 2014). When plant growth and substrate pH and EC data are taken together, 75 mg • L -1 N was determined to be the upper nutritional range limit, and plants fertilized with 100 to 400 mg • L -1 N were excluded from further statistical analyses.…”

“…The increasing con-sumer 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).…”

“…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.…”

“…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.…”

“…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.…”