Diana Stoll. "Agastache: An Herb for the Perennial Border." Llewellyn's 2019 Herbal Almanac: A Practical Guide to Growing, Cooking & Crafting. Llewellyn Worldwide, 2018. pna.ISBN9780738756578
Arthur O. Tucker and Thomas DeBaggio, The Encyclopedia of Herbs: A Comprehensive Reference to Herbs of Flavor and Fragrance. Timber Press, 2009. p. 127.ISBN9781604691344
ct.gov
"Connecticut's Endangered, Threatened and Special Concern Species 2015". State of Connecticut Department of Energy and Environmental Protection Bureau of Natural Resources. Retrieved 3 February 2018.(Note: This list is newer than the one used by plants.usda.gov and is more up-to-date.)