This organization goes back to the late 19th century.
From the membership page:
Membership in the New England Botanical Club is open to anyone with an interest in plants. Our membership includes both serious amateurs and professional plant biologists with interests in plant systematics, field botany, plant geography, plant ecology, paleobotany, conservation biology, genetics, population biology, and other specialties....
Members living in New England, New York and New Jersey receive monthly notices of Club meetings. More distant members should check the NEBC web site for news, meeting information and other Club information