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- Author or Editor: Terri A. Mellich x
Adenium obesum (Forssk.), Roem. & Schult., commonly known as desert rose, is a high-value, container-grown ornamental plant produced worldwide for its bright floral display and striking sculptural caudex. Little scientific-based information exists regarding the effect of light intensity and nutritional levels on Adenium growth and flowering. In this study, A. obesum ‘Red’ and ‘Ice Pink’ were grown under full sun [with a measured maximum photosynthetically active radiation (PAR) of 1850 μmol·m−2·s−1], 30% shade (1255 μmol·m−2·s−1), or 50% shade (943 μmol·m−2·s−1) in 1.25-L pots top-dressed with controlled-release fertilizer Nutricote® Plus (18N–2.6P–6.6K) at rates to provide 0.4, 0.9, or 1.4 g of nitrogen (N) per pot. Canopy height and width, flower number, and visual quality ratings (based on plant size and form, foliage color, and flowering) were highest after 16 weeks of growth for both cultivars when fertilized with 1.4 g of N per pot. A 30% shade level resulted in plants with the highest flower numbers and quality ratings. Plants grown at 50% shade had the greatest canopy heights and widths, but flower numbers and quality ratings were low. In full sun, plants were smaller overall. In a second experiment, A. obesum ‘Red’ produced the highest shoot dry weight when grown 20 weeks at 30% or 50% shade with 1.4 g of N per pot. Root formation is an important measure of aesthetic value for this crop. As plants mature, roots enlarge dramatically and are often washed to expose sculptural forms. The highest root dry weights were measured at 1.4 g of N under both full sun and 30% shade.
Adenium obesum (Forssk.), Roem. & Schult. has been increasingly produced as a flowering potted plant; however, there is no information regarding its tissue mineral composition. This study evaluated plant performance of A. obesum ‘Red’ grown in two container sizes and under four rates of a controlled-release fertilizer. Nutrient concentrations in flowers, leaves, stems, and roots were analyzed. Results showed that canopy height and width, stem caliper, top and root dry weights, and average flower count of A. obesum ‘Red’ increased linearly with the increased rate of fertilizer regardless of pot size. Tissue analysis indicated that nitrogen (N), phosphorus (P), and potassium (K) concentrations were lower in all organs compared with those reported for other ornamental potted plants such as Bouvardia Salisb., Euphorbia L., Rhododendron L., and Rosa L. The lower levels of tissue N and P accompanied with higher dry matter accumulation suggest that A. obesum ‘Red’ is efficient in use of N and P. The low tissue K levels were largely attributed to sodium (Na) substitution for K. Leaf K and Na concentrations were almost equal except at the highest fertilizer treatment in 1.25-L pots and the last two higher treatments in 3.0-L pots. The levels of other mineral elements were comparable to those of other reported ornamental potted plants. To produce high-quality plants in 1.25-L pots, Adenium ‘Red’ should be fertilized with 1.08 g N per liter of potting mix. For plants grown in 3.0-L pots, N rates of 0.36 g or 0.72 g per liter of potting mix would be recommended with a preference for 0.36 g.