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| Tips on cultivating Pittosporum tenuifolium | |
Plants of P. tenuifolium, especially the variety ‘Silver Queen’ are mostly grown for cut-branches. It is necessary to maintain plants in a condition of continued vegetative growth and to do this plants need feeding with NPK fertilizer at 1-0.3-0.5. As trees mature and the biomass increases, nutrient requirement grows proportionately. Local soils should be analysed to check the existing availability of Potassium. If high in Potassium this will accumulate in the tissues, especially in the woody and reserve tissues. Excess of Potassium can be alleviated by the application of Magnesium and Calcium but most effective of all by Ammonium Nitrate (Azoto Ammoniacale). Chemical analysis of leaf tissue has revealed the parameters required by the plants of a range of elements. Analysis of leaves from badly damaged plants that suffered the long period of high temperature together with dry conditions in the summer of 2003) was revealing. Boron accumulated in the leaves to the point of phytotoxicity. High levels of non-translocated Iron and Potassium were also found in the leaves and these factors contributed to a block of photosynthesis and growth of the plants. A parallel reduction in Nitrogen was also noted. It was found that tthe latter problem could be overcome by using substrates that contain Nitrogen but with inhibitors of nitrification. Nitrogen is released gradually over a long period and the acidity maintained at a level that improves the availability and assimilation of certain microelements from the soil. Controlling the levels of Potassium is very important. Potassium blocks vegetative growth and hardens the woody tissues. It is also an antagonist to the absorption of calcium which is required by the plants in quantities simular to that of Nitrogen. Poatassium is also antagonist to the absorption of Magnesium. Magnesium is a fundamental element in the cultivation of Pittosporum being a principal component of chlorophyll. Deficiency symtoms include a yellowing of the leaf veins to the point of chlorosis. Iron is very important, especially to the new vegetative growth. At extreme temperatures the available Iron is not assimilated. Iron availability is also reduced in calcarious soils. Phosphorus is not a significant element in this cultivation. Anna Benedetti, Ist. Sperimetale per la Nutrizione delle Piante, Roma. Giovanna Manchini e Pasquale Restuccia, Copa, Genova. Fiorenzo Gimelli, Ist. Regionale per la Floricoltura di Sanremo, Enrico Sparago, UCFlor. For further information of the important study“Colture Protette” 9, 2004. Fax 051 6575856 e-mail: cp@gce.it |
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