Nursery and Landscape Potential of Bog Birch, a Maine Native Shrub

Native ornamental plants, which are growing in demand in the U.S. horticulture industry, may promote biodiversity and wildlife habitat while improving landscape resilience. To succeed in the horticulture industry, novel introductions must be aesthetically pleasing, amenable to commercial propagation and production, and adaptable to variation in water availability typical of managed landscapes. Bog birch (Betula pumila) is a species that has the potential to meet these criteria, but limited horticultural literature is available. It is a small to medium colony-forming shrub native to northern North America with pubescent, ovate to obovate leaves that have the potential for outstanding fall color in tones of red, orange, and burgundy. Our research assessed the effects of drought on plant physiology, survival, and vigor, and the effects of auxin concentration and wounding during propagation of bog birch by softwood stem cuttings under intermittent mist. Water deficit was modeled in an automated irrigation system for a period of 8 weeks using Arduino UNO microcontrollers connected to soil moisture sensors and solenoid valves, allowing us to track and gradually decrease volumetric water content (VWC). Water potential, stomatal conductance, and rate of leaf photosynthesis declined in plants experiencing extreme drought (0.1 m3⋅m-3), with symptoms of leaf dieback and yellowing, whereas plants under moderate drought (0.15-0.2 m3⋅m-3) remained comparable in their leaf productivity and aesthetics to control plants, which were held at 0.4 m3⋅m-3. Bog birch overwintered in containers in a common garden after the study did not differ between treatments in growth and survival, except for a reduction in leaf biomass among plants that experienced drought. We also found that Arduino UNO microcontrollers are a low cost way to maintain VWC and log data in soilless substrates. Cuttings collected in northern Maine and treated with the potassium salt of indole-3-butyric acid (K-IBA) in solutions of 1,000 to 5,000 mg⋅L-1 produced greater root counts, root ratings, and longest root lengths than cuttings treated with water alone, with higher survival rates. Bog birch propagated from 5- to 6-inch cuttings and grown during one season in #1 nursery containers grew into upright, well-branched plants that were several feet tall. This research shows that bog birch is suitable for horticultural production, expanding native plant selection for consumers.