Among those plants which have just been mentioned as having been cultivated at various times for their honey alone, the linden for shade and ornament as well as for timber, catnip for sale as an herb or to secure its seed, and melilot for forage or green manuring are the only ones which, under present conditions, might in some cases be profitably cultivated. There may be introduced with advantage, however, all such honey-producing plants as, with one sowing or planting, will readily propagate themselves and without cultivation extend their area along roadsides and over waste lands, always excepting of course such as may become troublesome weeds. For this purpose most of the plants referred to above are available, and many others which like these are adapted to one portion or another of our country might be added, as, for example, pleurisy root or butterfly weed (_Asclepias tuberosa_), Indian currant or coral berry (_Symphoricarpos symphoricarpos_), viper's bugloss (_Echium vulgare_), lady's thumb (_Polygonum persicaria_), horsemint (_Monarda citriodora_), willow-herb (_Epilobium angustifolium_), etc., but of course it can not be expected that they will thrive and thoroughly establish themselves without further attention, except in such localities as present very favorable conditions for their growth. Furthermore, there is always the risk that a plant which yields honey abundantly in one part of the country may not do so in another region, even though it grows well, so that it is necessary in most cases, especially with wild plants, to test them anew before extensive introduction, no matter how well established their reputation as honey producers may be elsewhere. [Illustration: Fig. 47.--Summer or bird rape (_Brassica napus_).]