The lists given in this chapter cover the more common uses for which plants are selected. Perennial lists are not given because perennial plantings succeed according to the skill of the grower in adapting them to his location and giving them necessary winter protection. Constant care must be exercised to replace winter losses. The discussion in the main part of the foregoing text under the different lists and groups of plants applies equally well to most of the northern part of the United States, including Minnesota and adjoining territory.
Throughout this region spring planting is preferable to autumn, if it is done early enough, except of course for peonies and irises. In especially dry autumn weather autumn-planted stock is quite likely to prove a total loss. Ordinary shrubs and trees can be moved in the autumn under good conditions and this is also true of locally grown conifers moved in September; but other plants, and especially the perennials, should be moved only in the spring. Owing to the severity of the climate, especially in dry winters, sometimes without snow more than six inches deep, there is little tendency to encourage experimenting with half-hardy stock and most of the lists given are short.
These lists apply to an area within a two-hundred-mile radius of the Twin Cities in every direction. In eastern Wisconsin the Great Lakes would temper the climate, while northern Minnesota would be still more severe than at the Twin Cities, especially on sandy pine soils. Western Minnesota is quite similar, but a little more subject to drought and high winds. Central Iowa can grow a slightly larger list of plants because of a warmer climate and perhaps a little more rainfall.
In making a selection of plants from any of the other lists in this book for use in this region, first consult List XLIV-G to eliminate all types which have proved not hardy. The other lists may be consulted freely with this exception. All plants of questionable hardiness should be carefully protected.