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Release characteristics of four types of controlled-release fertilizers (Osmocote, Nutricote, Polyon, and Multicote) were studied during a 47-week simulated plant production cycle. The 2.4-L containers containing a low-fertility, acid-based substrate were placed in an unheated greenhouse and subjected to environmental conditions often used for production of azaleas and camellias. Leachate from containers was collected weekly and monitored for pH, electrical conductivity, and concentrations of NH4+ N, NO3–N, total P and total K. Leachate concentrations of all nutrients were relatively high during the first 10 to 20 weeks of the study, and then gradually decreased during the remaining portion of the experiment. Differences were observed among fertilizer types, with Multicote often resulting in higher concentrations of N, P, and K in leachates compared to the leachates from the other fertilizer types during the first half of the study. Concentrations of NO3– and P from all fertilizer types were often above permissible levels as cited in the federal Clean Water Act.

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We tested the hypothesis that premature leaf blackening in cut flower stems of Protea eximia (Salisb. ex Knight) Fourcade may be brought about by a low leaf carbohydrate status. Leaves on cut flower stems held in darkness blackened within 4 days, whereas those on stems held in a greenhouse remained healthy for 5 days. Leaf blackening was also retarded by supplying 1% sucrose in the vase solution; but other additives (hypochlorite, silver thiosulfate, bisulfite) were not effective. The hypothesis was further explored by examining postharvest carbohydrate changes in the leaf of cut flower stems held in light or darkness. At harvest, leaves contained very little hexose (< 1 mg·g-1 fresh weight), comparatively small concentrations of sucrose (≈ 5 mg·g-1 fresh weight) and starch (≈ 6 mg·g-1fresh weight), but high concentrations (≈ 30 mg·g-1fresh weight) of the polyol polygalatol. Starch and sugar contents of leaves held in darkness fell rapidly, to one-third of their initial level after only 1 day and to one-sixth after 3 days. In contrast, starch and sugar contents increased slowly in leaves of stems held in light to three times the initial level after 3 days. Polygalatol content was unaffected by any treatment. Removal of the inflorescence did not delay blackening of leaves held in darkness and did not affect their carbohydrate changes.