The Effects of Light and Soil Moisture on Propagation of Linnaea borealis

Linnaea borealis, or twinflower, is a clonal sub-shrub that is native to northern regions of the United States, Canada, Europe, and Siberia. It commonly grows in understory areas with partial shade, and soil moisture may be limited by competition for water with neighboring trees. Some growers report that this native plant is difficult to propagate, which is one reason that it is not abundantly available in the nursery industry. Twinflower populations are declining in some areas of the plant’s range. While twinflower prefers partial shade and grows in areas with limited moisture naturally, there has been no propagation work testing the impact of light or soil moisture conditions on root development of this plant. Therefore, our goal was to propagate twinflower under a variety of shade levels: 27.6, 14.4, or 5.8 mol•m^-2•d^-1 and Θ (volume of water ÷ volume of soil): 0.30, 0.35, 0.40, and 0.45 L•L^-1. Soil moisture was controlled using a capacitance sensor-automated propagation system. In order to avoid damaging native plants, we took minimal cuttings from two wild sources, a private property source and we obtained some cuttings from a grower collaborator. There was an interaction between the effects of light and soil moisture. However, the plants with the largest roots were grown at a DLI of 14.4 mol•m^-2•d^-1 and Θ of 0.30 or 0.35 L•L^-1. We also observed that the source of cuttings had an impact on survival. Cuttings taken from the source that was in the greatest amount of light had the lowest survival (26.7%) compared to cuttings taken from stock plants that were growing in partial shade (65% and 81.7%).