44 BULLETIN 791, U. S. DEPAETMENT OF AGRICULTURE. 



SUMMARY OF THE FOXGLOVE-SWEET-SAGE-YARROW CONSOCIATION. 



The foxglove-sweet-sage-yarrow cover, less speciiEically known as 

 the second or late weed stage, is the initial type in the retrogressive 

 succession of the porcupine-grass-yellow-brush consociation. The 

 more characteristic plants of this weed stage generally are compara- 

 tively aggressive where the conditions of growth are reasonably 

 favorable. A rather large number of species are associated with the 

 foxglove-sweet-sage-yarrow tj^pe species, though they seldom occur 

 as dominants. By far the greater number of the secondary plants 

 are nongrasslike. A few grasses are present, however, among which 

 large mountain brome grass is by far the most important. 



The type species and several of the secondary plants reproduce 

 both vegetatively and by seed. In several species vegetative repro- 

 duction is so active as to produce a loose matlike ground surface. 

 Most of the plants are shallow-rooted. When the soil conditions 

 become unfavorable for the maintenance of the foxglove-sweet-sage- 

 yarrow cover an aggressive succession of shallow-rooted, relatively 

 short-lived perennial plants in association with a number of annual 

 species usually takes place. In instances of severe soil depletion 

 annual species invariably predominate. 



Low pea vine, evening primrose, false cymopterus, Mexican dock, 

 and tongue-leaved violet are the most reliable and characteristic ini- 

 tial indicators of the destruction of the more stable second- weed- stage 

 cover. If the disturbing factor continues to operate, these rather 

 short-lived perennials are sooner or later superseded by annual plants. 



Much less dry matter and notably less palatable feed are produced 

 on the late-weed-stage type than on the wheat-grass or on the porcu- 

 pine-grass-yellow-brush consociations. The profusion of weed or 

 nongrasslike plants and the small amount of grass forage produced 

 makes the second- weed-stage cover better suited for the grazing of 

 sheep than for cattle and horses. Owing to the fact that sheep graze 

 nongrasslike plants with considerably greater avidity than cattle and 

 horses, the foxglove-sweet-sage-yarrow consociation can be fully 

 utilized by the grazing of sheep alone. Sheep, however, will not 

 show as much progress on the second-weed-stage consociation as on 

 the porcupine-grass-yellow-brush consociation. The gains may be 

 fairly large but the fat is not of a solid character. Cattle and horses 

 do poorly on the late weed type. As a rule, they little more than main- 

 tain their weight. 



THE RUDERAL-EARLY-WEED CONSOCIATION. 



Soils which were formerly rich but which have been so seriously 

 impaired that their fertility is similar to that of relatively new soils 

 recently invaded by herbaceous plants, support virtually the same 



