With respect to the plants reviewed in this book and the author's recommendations on plant culture, we will generally be considering plant culture in climates north of the midtemperatures between the Gulf of Mexico and Canada. This does not refer to a straight line east to west across mid-America since temperatures change with elevations. Although I have never gardened in Canada, I assume this would include the southern areas of our northern neighbor, as well as southern areas in the United States, which have higher elevations. As a precaution, I wish to remind people that various plants may be poisonous to taste and, for some people, to touch, so children in particular should be cautioned.