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.

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Commercially grown cultivars of Syngonium (Araceae) are very susceptible to Myrothecium leaf spot (incited by Myrothecium roridum Tode ex Fr.). Therefore, cultivation of Syngonium requires rigorous sanitation and frequent applications of fungicides for disease control. The goal of this research was to identify species and noncultivated accessions of Syngonium resistant to Myrothecium leaf spot. Five commercial cultivars and 30 accessions, comprising 16 different Syngonium species, were screened for resistance to M. roridum. All five commercial cultivars were susceptible to M. roridum. However, seven species (S. neglectum, S. wendlandii, S. dodsonianum, S. erythrophyllum, S. chiapense, S. dodsonianum, and S. angustatum) showed the highest resistance, as did two noncultivated accessions of S. podophyllum. The information on disease resistance for these species and accessions will be useful in future breeding work.

Botanical pesticides have received increasing attention for sustainable control of insect pests. Plants from the genus Tephrosia are known to produce rotenone and deguelin. Rotenone is known to possess insecticidal activities against a wide range of pests, but deguelin’s activities remain largely inconclusive. On the other hand, the biosynthesis of rotenone and deguelin may vary in Tephrosia species. This study analyzed the rotenone and deguelin contents in 13 strains across 4 Tephrosia species over 4 growing seasons using HPLC. Our study shows that the species and even the strains within a species vary substantially in the biosynthesis of rotenone and deguelin, and their contents can be affected by the growing season. After identification of the LC50 values of chemical rotenone and deguelin against Aphis gossypii (Glover) and Bemisia tabaci (Gennadius), leaf extracts derived from the 13 strains were used to test their insecticidal activities against the 2 pests. The results showed that the extracts derived from 2 strains of T. vogelii had the highest insecticidal activity, resulting in 100% mortality of A. gossypii and greater than 90% mortality of B. tabaci. The higher mortalities were closely associated with the higher contents of rotenone and deguelin in the two strains, indicating that deguelin also possesses insecticidal activities. This is the first documentation of leaf extracts derived from 13 Tephrosia strains against 2 important pests of A. gossypii and B. tabaci. The strain variation and seasonal influence on the rotenone and deguelin contents call for careful attention in selecting appropriate strains and seasons to produce leaf extracts for the control of insect pests.

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.