• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

GENERAL BOTANICAL CHARACTERISTICS

Green rabbitbrush is a low native shrub growing from 1 to 3.6 feet (0.3-1.1 m) with many brittle, erect stems branching from a compact base [57]. The species has a large geographic range and wide ecological amplitude. Leaves are deciduous [89]. Disc flowers are borne in terminal cymes [16]. The main taproot is at least 1.9 feet deep (0.6 m), and many major secondary roots extend laterally [61]. Plants are relatively short lived (approximately 12-13 years). Their senescence and attrition from some densely populated stands on early successional sites is related to infestation by larvae of the beetle Acamaeodera pulchella. Where green rabbitbrush is scattered within late-seral big sagebrush stands, there is a lower level of infestation [98].

RAUNKIAER LIFE FORM:

Phanerophyte

REGENERATION PROCESSES:

Green rabbitbrush produces an abundance of small, viable, plumed seeds [69,86]. Seeds are easily dispersed even long distances by wind [69]. A stratification period does not appear to be necessary but may speed germination. In eastern Oregon, seedlings established in grass and litter on the northeast sides of older rabbitbrush and sagebrush plants. They also established on north-facing slopes of small mounds or indentations made by animals. Seedling mortality in these sites was greater than 50% by June 12. Established seedlings do not persist unless late spring rains replenish soil moisture. Green rabbitbrush establishment during dry years is unlikely because seedling roots do not elongate deeply enough before surface moisture is depleted [59]. Seedlings do not appear to originate from seed banked in soil [98,99].

Green rabbitbrush resprouts vigorously [95].

SITE CHARACTERISTICS:

It is well adapted to drought and occurs in desert or semi-desert environments [6,20]. Green rabbitbrush grows on open ridges, on slopes, and along drainageways [38]. It grows on dry, well-drained medium to coarse-textured soils and exhibits fair salt tolerance [46, 55,69]. Green rabbitbrush grows on alkaline soils and exhibits an affinity for calcium [53].

Subspecies overlap in range but have somewhat different ecological requirements [58]. Chrysothamnus viscidiflorus ssp. lanceolatus is fairly common in dry foothills and mountainous habitats. Chrysothamnus viscidiflorus ssp. puberulus generally occurs at lower elevations on dry plains, valleys, and foothills, particularly on poorer soils and in disturbed areas. Chrysothamnus viscidiflorus ssp. viscidiflorus grows on soils with a pH of 6.0 to 8.4 [10].

Green rabbitbrush is most commonly found at elevations between 2,600 and 11,000 feet (790 and 3,350 m) [37,90]. Elevational ranges for several subspecies are as follows [10]:

Chrysothamnus viscidiflorus ssp. lanceolatus 976 to 11,000 feet (297-2,590 m)
Chrysothamnus viscidiflorus ssp. puberulus 4,200 to 10,000 feet (1,280-13,48 m)
Chrysothamnus viscidiflorus ssp. viscidiflorus 850 to 12,800 feet (259-3,901 m)

SUCCESSIONAL STATUS:

Green rabbitbrush quickly and aggressively invades disturbed open sites including burns and overgrazed rangelands [7,12,86,90]. It is a seral species in sagebrush communities and occupies disturbed areas such as burns after competing vegetation has been removed [28,29]. This shrub persists in small numbers in naturally disturbed areas such as washes, sand dunes, and talus slopes [100]. However, it attains dominance only on highly disturbed early seral sites [84]. Green rabbitbrush often remains dominant for the first 15 years after disturbance, but then declines and is replaced by species such as big sagebrush [90]. In a Nevada study, individual plants become senescent in about 12 years [101]. Longevity may vary with subspecies, however. Tueller and Payne [81] report that Chrysothamnus viscidiflorus var. latifolius persists for approximately 10 years. In pinyon-juniper communities, green rabbitbrush is considered an early to mid-seral species [43].

Green rabbitbrush may continue as a minor component in stands near or at climax condition [29]. Green rabbitbrush is much reduced in 40- to 50-year-old stands [45]. One reason for the limited longevity of some green rabbitbrush stands may be infestation by the larvae of Aemaeodera. Elimination of green rabbitbrush plants or reduction of vigor makes the site more susceptible to invasion by sagebrush or other late successional species.

SEASONAL DEVELOPMENT:

The phenological development of green rabbitbrush varies by elevation, climate, and infrataxa. Restricted vegetative growth begins in early spring, with a period of accelerated growth occurring in late spring. Vegetative growth levels off just before flowering [81].

Flowering usually begins in mid- to late summer [89]. Green rabbitbrush flowers during summer in all but the most extreme drought years [86]. Seed ripens from late fall to early winter [89]. Seeds generally begin sprouting in March and continue sprouting into June. The following table gives a generalized comparison of flowering development of various subspecies [24]:

Chrysothamnus viscidiflorus ssp. lanceolatus

            Begin        	Full            End
State       Flowering      	Flowering       Flowering
---------------------------------------------------------	
UT          May         	Aug.		Aug.
CO          June                Aug.            Sept.
WY          July                July            Sept.
MT          July                Aug.            Aug.

Chrysothamnus viscidiflorus ssp. viscidiflorus 

            Begin          	Full            End
State       Flowering      	Flowering       Flowering
---------------------------------------------------------
WY          July            	Aug.            Aug.
MT          May             	Aug.            Aug.

Phenological development for Chrysothamnus viscidiflorus ssp. 
puberulus in Idaho was [15]:

Leaf growth starts             	4/13
Twig growth starts             	5/24
Fl. buds visible               	6/30
First bloom                    	7/27
Full bloom                     	8/18
Bloom over                     	9/8
Seed ripe                      	9/2
Dissemination over               10/10

Young and Evans [97] report that green rabbitbrush (Chrysothamnus 
viscidiflorus ssp. viscidiflorus) undergoes 2 phases of 
branch elongation between bud burst and flowering.  A period of 
restricted growth in early spring is followed by accelerated 
growth in late spring and early summer. 

Related categories for SPECIES: Chrysothamnus viscidiflorus | Green Rabbitbrush