Julie Steele, Horticulture, Program Coordinator has shared the following links to help you answer your question about harvesting and processing lavender.
http://web.extension.illinois.edu/cook/downloads/9216.pdf
www.mountainvalleygrowerws.com
and www.homemade-gifts-made-easey.com
If you have additional questions you may reach Julie at jsteel@illinois.edu or 217-333-7672.
Good luck, Kathy