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

GENERAL BOTANICAL CHARACTERISTICS:

Spiny hopsage is a woody, erect, diffusely branched native shrub that reaches 1 to 5 feet (0.3-1.5 m) in height [7,23,27]. Branches are more or less spine-like at the tips [23]. Spiny hopsage is evergreen in the southern deserts and deciduous in the summer in the northern deserts [73]. Spiny hopsage is generally dioecious, although in some populations approximately 5% of the individuals are monoecious [7,8]. The fruit is a wing-margined utricle [62]. The root system is shallow and spreading [27].

Spiny hopsage is relatively long-lived [9].

RAUNKIER LIFEFORM:

Phanerophyte

REGENERATION PROCESSES:

Spiny hopsage regenerates vegetatively by sprouting after top-killing disturbances such as fire [9]. Spiny hopsage also regenerates from wind or gravity-dispersed winged seed, which is produced annually [37,46,66]. Seed production is variable. Plummer and others [44] describe seed production as "poor" in Utah whereas Daubenmire [9] reports that spiny hopsage produces an abundance of seed in Washington.

Persistent bracts apparently modify the microenvironment on the surface of the seedbed and aid in germination [83]. Light has little effect on germination of spiny hopsage [62]. However, habitat-correlated variation in germination patterns has been reported [39]. Populations from the northern part of the species’ range require cold temperatures to break dormancy [56]. Seeds readily germinate without pretreatment [79]. However, germination can be improved by cold stratification or dry storage [27,57]. Dormancy in spiny hopsage may represent an adaptation which delays germination until early spring when soil moisture conditions are most favorable [54]. Detailed information on germination and seed characteristics is available [54,58]. Germination patterns reflect spiny hopsage's ability to germinate either late in the fall or early in the spring while moisture is available [79]. Ecotypes apparently vary in germination response to temperature [73]. Seed fill is variable, ranging from 18 to 95% [62]. Spiny hopsage seed is reported to remain viable for 6 years in dry storage [62]. However, Plummer [46] rates the seeds as having good viability for 2 years. Some limited 2nd and 3rd year germination has been reported [57].

Spiny hopsage accumulates seeds in states of primary or even secondary dormancy within the soil in the Mojave Desert. Secondary dormancy occurs when nongerminating seeds enter dormancy in response to environmental conditions. Shaw and others [57] report "determining whether spiny hopsage seeds are capable of entering secondary dormancy and affecting factors will require further investigation." Seedbanks can contribute to periodic episodes of good seedling establishment during moist years. Seedlings require chilling in order for the bud to break and growth to occur [57].

SITE CHARACTERISTICS:

Spiny hopsage grows on dry plains, deserts, and foothill slopes throughout its range [37]. It is highly tolerant of drought [27].

Spiny hopsage is fairly tolerant of alkaline and saline soils [27] and is typically found on highly calcareous alkaline soils. Its adaptation to alkalinity is low relative to other salt-desert chenopods such as shadscale and black greasewood [37]. Some plants occur on neutral soils [7]. Spiny hopsage occurs on a wide range of soil textures from gravel, sand, and sandy loams to heavy clay [10,27,66], but it prefers sandy soils that are free of salt and hardpans [6]. Potassium is accumulated in spiny hopsage leaves and may comprise up to 63 to 73% of the total cations present. Spiny hopsage concentrates potassium in the surface soils beneath the canopy through decomposition of leaf litter [50].

Spiny hopsage grows from 524 feet to 9,514 feet (160-2900 m) in elevation [54]. Elevational ranges are as follows [10,64]:

4,000 to 7,000 feet (1219-2134 m) in Colorado
2,500 to 7,500 feet (762-2286 m) in Nevada
2,000 to 5,500 feet (610-1676 m) in Utah
4,100 to 6,800 feet (1,250-2073 m) in Wyoming

SUCCESSIONAL STATUS:

Spiny hopsage grows in a number of undisturbed sagebrush and saltbush desert shrub communities. It grows on disturbed sites such as coppice dunes [33]. According to Webb and others [75], it quickly reasserts dominance over colonizers on debris flows in the Panamint Mountains of California. The authors measured response rates of desert plants to disturbance in Death Valley National Monument. Plant assemblages were measured to quantify recovery rates and models developed to account for vegetative change based on principal component analysis following townsite abandonment, disturbances along a pipeline corridor, and on plant assemblages on new, several thousand-year old, and ancient (> 5,000-year-old) mud/debris flows. The following successional pathway has been proposed for mud/debris flows in Death Valley, California [74]:

1) annuals - filaree (Erodium spp.) and brome (Bromus spp.) colonize
2) lupine (Lupinus spp.)/saltbush (Atriplex spp.)/penstemon (Penstemon spp.)/
       buckwheat (Eriogonum spp.), and rabbitbrush (Chrysothamnus spp.) establish
3) wolfberry (Lycium spp.)/spiny hopsage/Nevada ephedra (Ephedra nevadensis) and blackbrush
4) spiny hopsage and Nevada ephedra dominate and initially colonizing species decline
5) blackbrush increases at the expense of Nevada ephedra, spiny hopsage, and wolfberry (may take more than 5,000 years)
6) blackbrush grows in nearly pure stands (may take 10,000 years to develop)

SEASONAL DEVELOPMENT:

Leaves of spiny hopsage generally appear in late February and early March [50]. In a Nevada study on the Great Basin-Mojave Desert interface, plants first leafed out from 2/2 to 3/20, with a mean date of 2/26 [68]. At a second Nevada site within the Great Basin, average leaf bud break took place on March 19 [54].

Spiny hopsage sheds its leaves much earlier than are those of many other deciduous desert shrubs [34]. In southern Nevada, leaves generally drop between mid-April and mid-May [69]. Leaves are usually shed by mid-July in most locations [6], but there is an ecotype in northern Utah that retains a higher percentage of leaves after the growing season [37].

Flowering is hastened by rainfall [68]. Most of the growth, including flowering and fruiting, is completed by midsummer [6]. In southern Nevada, first dates of flowering ranged from 2/26 to 4/9, with a mean date of 3/17 [68]. General flowering dates for four western states are as follows [1,10]:

  State      Beginning of Flowering      Flowering      End of Flowering
  CO         May                         May            July
  MT         June                        June           June
  NV         February/March              March          April
  UT         April                       May            June    

Dormancy in spiny hopsage is one of the longest of desert shrubs [54]. Spiny hopsage remains dormant throughout the hot, dry summer months [50]. In southern Nevada, Ackerman and others [1] found that spiny hopsage became dormant when daytime air temperatures exceeded 104 degrees Fahrenheit (40^oC). Summer rains will not cause initiation of new leaf growth [13]. Fall rains and/or periods of low temperatures ranging from 41 degrees Fahrenheit (5 ^oC) to below 32 degrees Fahrenheit (0 ^oC) usually break dormancy [1].

Related categories for SPECIES: Grayia spinosa | Spiny Hopsage