BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Purshia mexicana var. stansburiana | Stansbury Cliffrose 



GENERAL BOTANICAL CHARACTERISTICS : 
Stansbury cliffrose is a drought-resistant native shrub or tree.  It
usually grows from 1 to 6 feet (0.3-1.8 m) in height but may reach 25
feet (7.5 m) on favorable sites [93].  Plants in northern populations
are rarely over 12 feet (3.6 m) tall [10].  The simple, evergreen leaves
are small and alternate to clustered.  Leaves, flowers, and twigs are
glandular.  Twig and branch bark is shreddy.  The flowers are bisexual;
rarely, some are staminate.  The fruit is an achene with a persisent
style.  At one-half inch to 2 inches (1-3.5 cm), the style is several
times longer than the fruit [33,93,97].

Stansbury cliffrose has a taproot and much-branched, widely spreading
lateral roots.  Where not restricted by bedrock, the taproot grows
moderately deep.  In the Wasatch Mountains of Utah, Cline [19] excavated
roots of a 30-year-old individual that reached 8.8 feet (2.4 m) below
ground.  Roots may have nodules with nitrogen-fixing bacteria [60].

This is apparently a moderately long-lived shrub. Brotherson and others
[12] and Price and Brotherson [66] reported that the oldest living
Stansbury cliffrose in a population on the Wasatch Range of Utah was 69
years; 40 to 45 years was the modal age class.  Similarly, Cline [19]
found no individuals older than 69 years on a Wasatch Range site in Utah
County.


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Reproduction is by seed and, rarely, sprouting.  Stansbury cliffrose is
self-incompatible [8].  Plants first produce seed at about age 5 and
produce a good seed crop about every 2 years.  There is often more than
one seed set per season [1,102].  Heavily browsed plants usually do not
produce seed except on branches above browseline [39].  Seed readily
disperses when wind catches the long, plumose style.  Animals also
disperse seed [1,58].  Seed requires overwinter stratification (or 1-2
months cold stratification in the laboratory) and germinates in spring
[67,101,102].  Rodents cache Stansbury cliffrose seed, and seedling
clusters resulting from germination of uncomsumed seed are common
[Jensen and Stapley in (1),102].  Soil-stored seed remains viable for 5
[81,94] to 16 years [75].  There is no light requirement for germination
[94], and seeds germinate under a wide range of temperatures [101].
Fifteen to 100 percent germination has been reported in the laboratory
depending upon treatment and, probably, seed source [72,101].  Field
germination probably rarely exceeds 60 percent even under optimal
conditions [101].  Germination rates are usually higher in seed produced
early in the season than in later-maturing seed [1,102], and seed on
current-year growth may fail to mature [39].  

Price and Brotherson [66] found that seedling establishment was highest
in years of below-average precipitation in central Utah.  Still,
mortality from desiccation is high in germinants.  Early growth is
mainly below ground; seedlings have a high root:shoot ratio [19].  Dense
stands of exotic annual grasses may competitively exclude Stansbury
cliffrose seedlings [66].

Variable sprouting ability is reported for Stansbury cliffrose, and it
is uncertain whether the variation is due to genetics, degree of damage
to the root crown, or a combination of both.  Stansbury cliffrose is
anecdotally reported as nonsprouting in California [73], nonsprouting to
weakly sprouting in Arizona and New Mexico [74], and sprouting in
western Nevada [Klebenow and Bruner in (61)].  Multistemmed individuals
have a greater tendancy to sprout than single-stemmed individuals [95].
McCulloch [53] reported that on the Kaibab Plateau, plants bulldozed to
the root crown did not sprout, while those sustaining only top-crown
damage sprouted from the root crown.


SITE CHARACTERISTICS : 
True to its name, Stansbury cliffrose occurs on cliffs and other
exposed, dry sites such as mesas and foothills [1,32,56].  Aspect is
usually south or west [35,66].  Limestone is the most common substrate
parent material, but Stansbury cliffrose also occurs on other
sedimentary substrates and also on igenous formations [17,22,31,66].
Soils are acidic to alkaline [10], well-drained [51], and have a coarse
sandy, gravelly, or rocky texture [32,94].  Stansbury cliffrose can
survive on sites receiving less than 12 inches (305 mm) of annual
precipitation [10].

Elevational range by state is:

            feet           meters          state
        3,000-8,000       914-2,438      AZ [17,41]
        3,630-7,500     1,100-2,500      CA [33]
        2,525-8,235       975-2,745      UT [66,97]


SUCCESSIONAL STATUS : 
Stansbury cliffrose seedlings colonize open, disturbed sites [61].  As
adults, plants are "fairly" shade tolerant [95].  Stansbury cliffrose
occurs in understories of open coniferous forests [14,31,48,] but is
probably shaded out with canopy closure.  In desert shrublands,
Stansbury cliffrose may persist for 60 years or more, although
individuals over 69 years of age have not been found [66].


SEASONAL DEVELOPMENT : 
Flowers first appear from early May to late June, with blooming
continuing until first autumn frost.  Seeds from the earliest flowers
mature and disperse from mid-July to August in Utah, with later-produced
seed ripening and dispersing through October [1].  Arizona and
California plants flower from April to September [41,59], with seed
ripening and dispersing through October [73].

Related categories for Species: Purshia mexicana var. stansburiana | Stansbury Cliffrose