BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Zuckia brandegeei | Silt Bush 



GENERAL BOTANICAL CHARACTERISTICS : 
Silt bush is a native, perennial shrub or subshrub that grows from 0.5
to 1.6 feet (10-50 cm) in height [18].  The slender, erect or ascending
annual stems are branched from a persistant woody base 2 to 8 inches
(5-20 cm) tall [2,18].  The branches lack spines [6].  Leaves are
alternate with linear-oblanceolate to obovate blades and reach 0.6 to
1.8 inches (1.5-4.5 cm) in length [1,6].

Identification between the chromosomal races proposed by Stutz and
others [16] is possible due to variations in stature and leaf size.
Diploid populations (Z. brandegeei var. brandegeei) grow 0.8 to 1.3 feet
(2-4 dm) tall and have narrow linear leaves, while the larger statured
tetraploids (Z. brandegeei var. plummeri) reach 0.10 to 1.6 feet (3-5 dm)
in height and have wider, more oval-shaped leaves [10,16].

Silt bush has been desbribed as dioecious or less commonly monoecious
[2,6,17].  Pendleton [10] has, however, shown silt bush to be
monoecious.  The only exceptions were found on plants where the second
sexual function failed to mature [10].  Silt bush is heterodichogamous;
separation of sexual functions is complete [10].  Environmentaly induced
sex changes have been reported [9].

Silt bush has a spreading root system that provides good resistance to
drought [7].  It often grows on saline and seleniferous soils [17] and
has been listed as a possible secondary or facultative selenium absorber
[1].


RAUNKIAER LIFE FORM : 
   Hemicryptophyte


REGENERATION PROCESSES : 
Silt bush reproduces by winged seed which is produced annually [13].  It
is reported to germinate and produce seedlings readily [1].  Germination
is improved by cold stratification or dry storage [7].

Silt bush also regenerates vegetatively.
 


SITE CHARACTERISTICS : 
Silt bush is generally restricted to the drier plains and foothills in
the Upper Colorado River drainage [7].  One isolated population occurs
in the Great Basin [16].  Stutz [15] found silt bush grew almost
exclusively on talus and steep mud slopes.  These steeper sites show
little soil development [10].  Growth is reported to be good on gentle
to moderate slopes and fair on steep [3].

Silt bush occurs on a variety of soils that range from sandy, loamy,
silty clay loam, to clayey in texture [3,7].  It is typically found on
heavy clay substrates derived from shale, but it will occur on flatter,
sandier sites in the southern extension of its range [10].  Soils are
often saline and seleniferous [17].

The chromosomal races of silt bush are reported to grow in soils with
slight differences in mineral content.  Stutz and others [16] found
diploid populations occupied soils higher in iron and manganese, while
soils occupied by tetraploids had consistently higher contents of
potassium and zinc [16].

Silt bush is adapted to juniper-oak woodlands, pinyon-juniper sites, and
salt desert shrublands [2,9,11].  It may occur in pure stands but is
often found growing in association with Stansbury cliffrose, shadscale
(Atriplex confertifolia), big sagebrush (Artemisia tridentata), and
blackbrush (Coleogyne ramosissima) [10,11].  Silt bush occurs from 3,000
to 7,000 feet (900-2,100 m) in elevation [7].  Elevational ranges for
several western states are as follows [3]:

         from  5,000 to 6,000 feet (1,524-1,982 m) in CO
               4,800 to 8,000 feet (1,463-2,439 m) in UT
               6,800 to 7,300 feet (2,073-2,225 m) in WY


SUCCESSIONAL STATUS : 
Silt bush is reported to increase after disturbance [9].


SEASONAL DEVELOPMENT : 
Information on the phenological development of silt bush is scant.  It
can be in full leaf by early to late May [9].  The leaves appear in
early April and dehisce in late summer [16].  The flowering period
varies from mid-June to mid-August [1].  Pendleton [10] reported that
flowering begins sometime in May and fruit set is complete by early
July.  The leaves continue to develop after fruit set and become thick
and leathery [10].  Generalized flowering dates for silt bush in several
western stated are as follows [3]:

 State       Beginning of Flowering       Flowering       End of Flowering
  CO                 July                    July              August
  UT                 June                    July              August
  WY                 July                    July              August
                                             
Seed ripens in late September to early October, but the utricles remain
on the plant until January [1].  Smith [13] reported fruit ripening
begins in September and lasts until mid-December.  Fruits may persist on
the plant through the winter but are often eaten by small mammals and
birds [1].

Related categories for Species: Zuckia brandegeei | Silt Bush