APRIL 

 5 10 15 20 25 

 J I I I L. 



MAY 

 5 10 15 20 25 

 J I I I I 



JUNE 

 5 10 15 20 25 

 J I I I I 



JULY 

 5 10 15 20 25 

 J I I I I 



AUGUST 

 5 10 15 20 25 

 J — I I I L_ 



SEPTEMBER 

 5 10 15 20 25 

 J I I ' I 



Danthonia 

 intermedia 



Festuca 

 idahoensis 



Koleria 

 cristata 



Stipa 



occidenta/is 



Agropyron 

 spicatum ' 



T — I — I — I — r- 



5 10 15 20 25 

 APRIL 



X — ^ 



-Ox— 



T — I — I — I — r- 



5 10 15 20 25 

 MAY 



-I — I — I — I — r- 



5 10 15 20 25 

 JUNE 



1 — I — I — I — r- 



5 10 15 20 25 

 JULY 



-| — I — I — I — T" 



5 10 15 20 25 

 AUGUST 



1 — I — I — I — r 



5 10 15 20 25 

 SEPTEMBER 



' No seed produced during 5-year period because of heavy insect infestation. 

 Legend: | Growth Starts, <• Flower Stalks Appear; ® Bloom; X Drying Starts; ^ Dissemination Starts; 1 Plant Dried. 



Figure 2. — The 5-year mean of developmental events for grasses 

 on a southwest exposure at 7 ^lOO-ft. elevation. 



The maximum difference between years in time of first bloom for the six early- 

 flowering forbs ranged from 18 to 33 days (average was 22 days). This difference was 

 about the same for the six forbs that bloom in midseason. However, the maximum 

 difference between years in time of first bloom of the 11 late-flowering forbs ranged 

 from 8 to 21 days and averaged only 12 days. The difference between the earliest and 

 latest dates of full bloom corresponded closely to that for first bloom for all three 

 groups of species. Apparently, temperature is a dominant factor in control of flowering 

 of species that bloom early or in midseason. Retarding effects of a late spring and 

 accelerating effects of an early spring are still effective in early June when the mid- 

 season plants begin to flower, but have little effect by the time the late-blooming 

 species start to flower in late June and early July. The reduced yearly variation in 

 date of flowering of the late-blooming species could reflect this group's greater 

 dependence on photoperiod than on temperature control of flowering. 



The greatest difference between years in the date of flower stalk appearance for 

 the grasses ranged from 10 days for Danthonia to 28 days for Festuca; it averaged 

 17 days for all five species studied (table 2). Yearly differences were reduced to an 

 average of 11 days (6 days for Agropyron to 19 days for Danthonia) by the time these 

 grasses flowered. Interestingly, the date of blooming for Festuca varied relatively 

 little between years (8 days), and Danthonia varied greatly (19 days); this was just the 

 opposite of the variation that existed when the flower stalks first appeared. Average 

 elapsed time between first appearance of flower stalks and blooming was 14 days for 

 Danthonia, 18 days for Stipa, and approximately 23 days for Agropyron, Festuca, and 

 Koeleria. 



The duration of flowering (fig. 1) denotes the time each species of forb had a 

 floral aspect. The precise date of flowering differed between individual plants of the 

 same species; this difference was much greater in some species than in others. 

 Lomatium and Achillea prolonged their floral aspect over at least 4 weeks, whereas that 

 of most species usually lasted 2 to 3 weeks. 



7 



