Sphagnum productivity declined in response to imposed warming treatments in an ombrotrophic bog in northern Minnesota (https://mnspruce.ornl.gov). Nearly complete loss of Sphagnum cover occurred at the highest temperature in the experiment (+9°C), and growth was reduced in response to elevated CO2. Some of this response may be due to reduced light availability with increasing shrub cover. We conducted a side experiment to determine the response of Sphagnum to shading similar to that created by the shrubs using shade cloth of different density (0-90%). Sphagnum production decreased in response to increasing shade, but addition of shrub leaf litter had no effect.