Field guides are such a good idea and Teresa’s is one of the best I’ve used.  Even better, Teresa Marrone is a local author - she resides in Minneapolis.  Her other guides are to be recommended as well. 

A little history of Field Guides paraphrased from Wikipedia:

Perhaps the first popular field guide of plants in the United States was the 1893 How to Know the Wildflowers by Mrs. William Starr Dana (Frances Theodora Parsons). Mrs. Dana’s reference was for the lab rather than a portable book for the field. It was arranged by taxonomic order and had clear descriptions of species size, distribution, feeding, and nesting habits.

Before her, in 1890, Florence Merriam published Birds Through an Opera-Glass, describing 70 common species.

From this point into the 1930s, features of field guides such as changing the size of the book to fit the pocket, including color plates, and producing guides in uniform editions that covered subjects such as garden and woodland flowers, mushrooms, insects, and dogs were introduced by Chester A. Reed and others.

In 1934, renowned ornithologist Roger Tory Peterson (1908–1996), using his fine skill as an artist, changed the way modern field guides approached identification. Using color plates with paintings of similar species together – and marked with arrows showing the differences – people could use his bird guide in the field to compare species quickly to make identification easier. His inaugural volume was the classic 1934 book A Field Guide to the Birds.  Peterson Field Guides are essentially the standard today.

Back to WEEDS.  Field guides are designed for identification when out and about.  Clear photos, good descriptions, easily skimmed subtitles, notes about habitat, and necessary warnings are expected.  Teresa delivers all this well but WEEDS offers more: comparisons to similar plants for detailed ID, notes on how to eradicate (if possible) and, my personal favorite, “What’s It Good For?”.  Many weeds are edible by us or useful for medicinal purposes, serve as a key food source for other creatures, serve purposes such as erosion control or producing good dyes, or are a source of soil regeneration.  Or are just plain attractive and effective as a ground cover.  She manages to pull out the good in almost every “weed”.  I have found that her guide covers the weeds we are likely to see here.  Other guides I have are more comprehensive, intended for a larger region, but take more effort to locate the plant that I am seeing.

Personally I credit black medick (Medicago lupulin), (pp. 42-43)  a legume and prolific seeder, with transforming a garden area that was once practically concrete to the best soil in my yard.  Over several years of growing, dying, decaying and reseeding for a repeat, these plants broke up the soil and added nitrogen to it.  Today they are hardly present as other plants have thrived in their place. As is said, a weed to one, is not so much that to another. 

Photo credits: Book cover (1), book exerpt (2)