Seed germination, seedling inoculation and establishment of Alnus spp. in containers in greenhouse trials.
Methods for production of containerized seedlings of A. incana subsp. rugosa [A. rugosa], A. glutinosa and A. rubra were developed which permit nitrogen-fixing nodules to form on the root systems prior to outplanting, in order to provide an early N input during establishment. The methods are based on procedures for inoculating root systems with suspensions of Frankia, applied either directly in the container cell as a soil drench at the time of sowing, or as a root dip for seedlings transplanted into the containers. Germination of dried, stored seed was enhanced by light and by presoaking for 16 h in water. Pretreatments to overcome seed dormancy or to eliminate fungal pathogens did not further enhance germination. Some loss of seedlings was recorded in the early stages of growth shortly after germination, which is a factor in calculating projected seedling yield. Nodulation and seedling growth were evaluated in terms of growth media characteristics. Seedlings performed well in peat-vermiculite, at soil pH between 5.5 and 8.0.