BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Hymenoclea salsola | White Burrobrush 



GENERAL BOTANICAL CHARACTERISTICS : 
White burrobrush is a native, short-lived, drought-deciduous, perennial
shrub 3 to 8 feet (1-2.5 m) tall and two- or three-fold as wide
[2,4,22,27].  It is rounded and often straggly with slender, puberulent
branches and narrow, often threadlike or needlelike leaves to 0.7 to 3
inches (2-7.5 cm) long [7,18,21,27].  The flower heads are small and
numerous [2,7,22].  White burrobrush has a shallow root system
consisting of a relatively short taproot with prominent laterals [20].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
White burrobrush reproduces mostly by seed but can also reproduce by
sprouting [13,29,41].  Flowers are borne on 2-year-old branches which,
following fruit development, die back to the ground.  Flowers are wind
pollinated [21].  White burrobrush fruits contain only one seed and are
disseminated by wind or water [19,21,37].

The seeds have high viability and germination rates compared to other
desert shrubs [26,41].  In a 16-day germination study, they had one of
the highest rates of germination (57 percent) of seven species of desert
shrubs.  White burrobrush seedlings emerged well from 0.39- and
0.79-inch (1- and 2-cm) plantings but not from depths of 1.5 inches (4
cm) or more [41].  Stratification has been shown to have no effect on
germination rate.  Seed treatments used to increase white burrobrush
germination in the laboratory, and their results, have been described by
Graves and others [13].


SITE CHARACTERISTICS : 
White burrobrush is commonly found in sandy washes, alluvial fans, and
rocky slopes [2,18,21].  It generally grows on well-drained, sandy,
alkaline soils [22,33], and is found at elevations between 2,200 and
2,950 feet (670-900 m) [39].


SUCCESSIONAL STATUS : 
Obligate Initial Community Species 

White burrobrush is a short-lived pioneer or invader species.  It is
common and often very abundant on disturbed sites [24,34,35].  White
burrobrush is often the primary short-lived pioneer species found in
small desert washes [36].  It may be present in very low numbers in
stable, old creosotebush communities [36].  The life span of white
burrobrush is not known but is estimated at only a few decades [34].

White burrobrush was the most abundant pioneer shrub on a disturbed
pipeline construction site in creosotebush scrub vegetation of the
Mojave Desert.  In some disturbed areas white burrobrush made up as much
as 85 percent of the vegetative cover 12 years after the original
vegetation had been removed [35].  Another Mojave Desert study of
disturbed creosotebush scrub, at three military camps abandoned for 40
years, found that white burrobrush was dominant in the majority of
disturbed sites.  It also had percentage cover values similar to or
greater than controls in most areas where substrate alterations were
significant [24].


SEASONAL DEVELOPMENT : 
White burrobrush flowers from March through June [1,18,20,22].  New leaf
and twig growth is initiated after summer and winter rains.  Both leaf
and twig tissues are thus present during the periods of peak seasonal
productivity [6].  At one site in southern Nye County, Nevada, the range
of beginning dates of phenophases over a 6-year period was as follows
[1]:

     leaf- March through April
     flower bud- mid-March through mid-April
     flower- early April through early May.

Related categories for Species: Hymenoclea salsola | White Burrobrush