Doctoral Dissertations

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Plant, Soil and Environmental Sciences

Major Professor

B. S. Pickett

Committee Members

Homer D. Swingle, John H. Reynolds, Hendrik van de Werken, David L. Coffey


The purpose of this study was to evaluate hardwood bark as an organic component of media for container-grown Japanese holly (Ilex crenata 'Hetzi'). The evaluation included the effect of species of bark, particle size of bark, and ratio of bark to media on the growth of Japanese holly. The bark was treated with polyvinyl alcohol to determine its effect on the rate of decomposition and possible toxic effects of the different species of bark. The evaluation included plant responses and laboratory analyses of the plant material and media. The growth responses measured were: fresh weight, dry weight, percent dry weight, stem diameter, and relative growth rate. The dried leaf tissue of the plants was analyzed for nitrogen, phosphorus, potassium, calcium, magnesium, and iron con-tent. The media were analyzed to determine their chemical composition, pH, cation exchange capacity, total soluble salts, bulk density, and percent shrinkage. The media composed of 100 percent peat produced plants which were superior to plants grown in any other media. Plants grown in media con-taining 50 percent hardwood bark and 50 percent sand, with the exception of media containing ash bark and poplar bark, produced plants which were as good, and in some cases better than, plants grown in a 1:1 mixture of peat and sand. The plants grown in media containing poplar bark and ash bark were smaller and generally inferior to plants grown in peat and sand. The finer of the two particle sizes of bark incorporated into the media produced better plants as an average of all media. Plants grown in media composed of 50 percent bark and 50 percent sand were generally superior to plants grown in a 100 percent bark media. The treatment of bark with polyvinyl alcohol had no significant effect on plant growth or rate of decomposition of the bark. There was no evidence that toxic substances were released from any of the bark species. The chlorosis which developed in plants grown in some of the bark media was believed to have been a symptom of iron deficiency caused either by high pH or improper nutrient balance in the media.

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