Jil was born in Louisville, Kentucky, in 1956, and is the youngest of five children. Over the years her family lived in San Jose, California, Slidell, Louisiana, Dallas, Texas, Las Vegas, Nevada, and eventually Alexandria, Virginia. She lives with her husband Warren Steiner and their four fabulous felines in Cheverly Maryland. Jil attended the Alexandria Campus of Northern Virginia Community College where she took a “Regional Flora” class that inspired her interest in plant taxonomy. She transferred to George Mason University in Fairfax, Virginia and completed her B.S. in Biology in 1979 with an emphasis in botany. In 1980 and 1982, she took graduate courses in entomology, evolutionary ecology and pteridology at the University of Virginia’s Mountain Lake Biological Station and worked as a research assistant. She transferred to George Mason University to complete a M.S. degree in Systematics, Evolution and Population Ecology. Her thesis research was on the foraging ecology of native ants which disperse seeds of several spring-flowering plant species.
Over the years, Jil has worked for the Smithsonian Natural History Museum Paleobotany and Entomology departments, the U.S. Fish and Wildlife Service Endangered Species Office and Wildlife Permit Office, the Baltimore County Department of Environmental Planning, the Maryland-National Capital Park and Planning Commission, and since 1995, the National Park Service. For NPS, Jil serves as IPM and Invasive Species Specialist for the National Capital Region and helps the parks with management, prevention and monitoring of pest insects, plants and pathogens. Jil created the "Weeds Gone Wild" website, developed the WeedUS Database of Plants Invading Natural Areas in the U.S., and founded the Mid-Atlantic Exotic Pest Plant Council. She is lead author of the book Plant Invaders of Mid-Atlantic Natural Areas and recently co-developed the new “Invasive Plant Atlas of the United States” in collaboration with the University of Georgia Center for Invasive Species and Ecosystem Health.
Jil is currently President of the Entomological Society of Washington and past president of the Botanical Society of Washington. She was elected to membership in the Washington Biologists’ Field Club in 2007. She enjoys natural history, photography and playing hammered dulcimer with her husband, Warren, who is a member of the Washington Biologists’ Field Club, and with friends.