Here’s a running list of resources used in entries:
Wikipedia – Hear me out here – I’d never advocate using this as a primary resource, but if you have a reasonably good idea of what you’re looking for (a species name is ideal here), Wikipedia is a great gateway to primary resources.
Niering, W. A. and Olmstead, N. C. (1983). The Audubon Society Field Guide to North American Wildflowers: Eastern Region. New York: Alfred A. Knopf – I’ll admit this book has a somewhat special place in my heart. I attended Connecticut College, and I was privileged to take one of Professor Niering’s Connecticut Plants courses – I believe it was the last time he taught that particular class before he passed away. Absolutely an amazing man, with an amazing knowledge of plants.
Kaczmarek, Frank. (2009). New England Wildflowers: A Guide to Common Plants. Guildford, CT: Falcon Guides – This book has supplanted the above as my first go to. It’s arranged by color, and the index goes by both common and scientific names. It’s fairly comprehensive too, so I can a fair amount with just a little perusing.
Elliman, Ted & New England Wild Flower Society. (2016) Wildflowers of New England. Portland, OR: Timber Press, Inc. – This is my newest purchase, and has quickly become my favorite. It’s arranged by color and petal type, so other than the white flower (so many white flowers!), it’s fairly quick to look through. I’m now starting here first. I only wish it covered trees and larger shrubs.
Go Botany The New England Wild Flower Society’s database of New England Plants. Has natives and introduced species. and a key online you can use to help figure out what plant you’re looking at. I use this a lot when I’m stuck on something, and it’s great for trees and shrubs, since those are often skipped in general wildflower information.
US Wildflowers Database of Wildflowers for Maine– Good database if you’re willing to trawl through a number of thumbnails. It’s in alphabetical order by common name, which can get confusing if you don’t know the right common name.