Date of Award

Fall 1981

Project Type


Program or Major

Plant Science

Degree Name

Doctor of Philosophy


The use of fresh, inprocessed bark as a component of a soil-less medium for selected pot grown floriculture crops was evaluated.

Blends of bark of northern hardwood and softwood tree species from two New Hampshire sources were physically and chemically characterized. Measurements included N, P, K, Ca, Mg, pH, and total soluble salts on growing media and spectrographic analyses of plant leaves.

Observations, including height and fresh weight, of the chrysanthemum cultivar "Bright Golden Anne" (Chrysanthemum morifolium Ramat) in media containing various amounts of the two bark blends in combination with vermiculite and perlite were evaluated. Treatments consisting of various formulations and rates of the slow-release fertilizers Magamp and Osmocote were applied in three separate experiments. In a fourth experiment, four different rates of NH(,4)NO(,3) were compared with a 20-20-20 fertilizer application.

The data indicated that Osmocote produced taller, heavier, and generally better quality plants than Magamp with most hardwood bark mixtures but not significantly better plants in softwood mixtures. This was attributed to the higher NO(,3) content of Osmocote and the more rapid rate of decomposition and subsequent demands for soil nitrogen in hardwood bark mixes. The higher rates of any of the fertilizer treatments produced the best plants. Raw bark media must be fertilized with sufficient nitrogen at a rate of at least 400 ppm per week applied in enough quantity to thoroughly saturate the volume of the container used.

While raw screened bark can be utilized as a growing medium, best results were usually obtained when bark constituted between 50 percent and 75 percent of the total mixture by volume. Coarse particles in both the fresh hardwood and softwood mixtures created greater aeration and drainage than comparable products. Vermiculite was the best overall inorganic component throughout the experiments.

When properly watered and fertilized, mixtures of hardwood and softwood bark can be effectively used as the organic component in an artificial growing medium for container-grown florist crops.