Enhancement of germination in native woody species with particular reference to Rosa corymbifera Laxa.

Abstract

Commercial production of native tree and shrub species from seed can be unpredictable. Rosa corymbifera 'Laxa' is one such species of commercial importance as a rootstock, and is characteristic of the Rosaceae family. During the investigation, a standard commercial pretreatment was used to determine the unpredictable nature of this species with regard to germination. It was found that germination varied from as low as 2% in one year to a high of 63% in a subsequent year. The average germination was 26% over this period. This presents a very real dilemma to the grower with respect to meeting demand from highly unpredictable species. This dilemma is inherent in native tree production from seed. Germination became high and predictable with the addition of a compost maker, Garotta. During the same five year period the lowest germination achieved was 75% and the highest 99%. The average germination was 89%. Germination was vastly increased in percentage terms as well as becoming reliable from year to year. The benefits to the grower in using this technique are potentially great in terms of time and resources. Not only is this pretreatment highly predictable, it is safe and easy to apply, unlike alternatives such as the use of concentrated sulphuric acid to burn off the seed coat. During the pretreatment of Rosa corymbifera'Laxa' the influence of microorganisms was assessed. Microbes were found within the pretreatment and their presence was established as being required to overcome the dormancy of the seeds. Low microbial numbers and activity were found in the commercial pretreatment, resulting in low germination. High microbial numbers and activity were found in the Garotta pretreatment, resulting in high and predictable germination. Total absence of microbes was found to result in zero germination.