18 The Plant World, 



elm (Ulmus americana), black walnut (Juglans nigra), English 

 walnut Juglans regia), camphor tree (Camphora officinalis), 

 smoke tree {Rhus cotinus), white poplar {Populus alba), common 

 lilac, common weigela, native red-bud {Cercis canadensis) , mock 

 orange (Philadelphus inodorus), deutzia (Deutzia scabra), and 

 snowball (Viburnum opulus), besides numerous spiraeas and 

 roses. With these plants growth is usually normal until May 

 or June, after which they are comparatively inactive for the 

 remainder of the season, or in certain instances growth may 

 begin again with the cooler temperatures of late summer and fall. 

 In the summer season, they do not present a healthy 

 appearance. 



As concerns herbaceous species it is practically impossible 

 to maintain at the lower altitudes in Arizona during the summer 

 season, stands of such grasses as timothy (Phleum pratense), 

 red top {Agrostis alba), sheep's fescue (Festuca ovina), blue grass 

 {Poa pratensis), orchard grass {Dactylis glomeraia), or smooth 

 brome grass {Bromus inermis) even on lawns where far more 

 than ordinary attention is given. No one thinks of growing 

 any of these as hay or meadow plants, although all are hardy 

 grasses in the states to the north and east of us. These species 

 grow fairly well throughout our fall, winter and spring months, 

 but with enough irrigation to make good growth possible under 

 ordinary conditions, their foliage bums and they die out in the 

 summer season, except in the shade of trees or other protection. 

 When several of these species were grown in similar soil under 

 lattice so as to reduce extreme heat and light, they appeared 

 nearly normal; and in parts of Arizona where the maximum 

 temperatures seldom exceed 95 degrees F. they present a thrifty 

 appearance with the usual irrigation. There can be little doubt 

 therefore, that extremes of heat and light, or both these condi- 

 tions are responsible for the failure of these plants. 



This same condition obtains in the instance of such other 

 well-known herbaceous plants as paeonia, dahlia, columbine 

 (Aqiiilegia), golden glow (Rudbeckia), gladiolus, grass pink 

 (Dianihus), summer hyacinth (Galtonia), common tansy (Tana- 

 cetuni vulgare), rosemary or costmint {Chrysanthemum) , bouncing 

 bet {Saponaria) , perennial phlox, and perennial larkspur {Del- 

 phinium), in addition to the garden plants, horse radish, and 

 rhubarb or pieplant. Except under lattice or in the shade of 



