Abstract

Rhamnus alnifolia L'Her (Alderleaf Buckthorn) and Rhamnus lanceolata Pursh ssp. lanceolata (Lanceleaf Buckthorn) are native shrubs that are uncommon in the wild. Seed germination of both species and vegetative propagation of R. alnifolia was studied. Germination was low (≤ 13%) among moist-prechilled seeds of R. alnifolia collected in mid-season, but 48% germination was observed among seeds collected late in summer and moist-prechilled for 30 days. Nontreated seeds did not germinate, nor did seeds first scarified with sulfuric acid or hot water followed by moist-prechilling. Germination was ≤ 5% among seeds of R. lanceolata and occurred only after seeds were moist-prechilled for at least 90 days. Seedling survival among both species ranged from 90 to 100% and was not influenced by pregermination treatment. Rooting among softwood cuttings of R. alnifolia was 85% within 35 days after application of 3 g/kg (3000 ppm) or 8 g/kg (8000 ppm) indole-3-butyric acid (IBA) in talc. When IBA was applied in acetone solution at 3 and 8 g/liter (3000 and 8000 ppm), rooting was ≤ 15%. While 75% of the nontreated cuttings rooted, these cuttings had fewer roots than those treated with IBA. Rooting was more extensive in vermiculite compared to a medium of equal volumes of vermiculite and perlite. Talc-based IBA and vermiculite should be used to induce root formation on softwood stem cuttings of R. alnifolia. Both R. lanceolata and R. alnifolia can be propagated from moist-prechilled seeds, but Rhamnus lanceolata is recalcitrant and merits further assessment of drupe phenology, timing of seed collection, and barriers to germination.