BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Descurainia pinnata | Pinnate Tansymustard 



GENERAL BOTANICAL CHARACTERISTICS : 
Pinnate tansymustard is a native, annual, cool-season forb [18].  It
grows from 4.2 to 31.2 inches (10-80 cm).  The erect stem is simple or
freely branched [19].  Flowers are borne in racemes up to 11.8 inches
(30 cm). Plants are showy when flowering but become ragged and
inconspicuous as seed matures.  Pinnate tansymustard has a deep taproot.


RAUNKIAER LIFE FORM : 
   Therophyte


REGENERATION PROCESSES : 
Pinnate tansymustard regenerates through an abundance of small seed
[18].  One to twenty biseriate, clavate, or elliptic seeds are produced
per locule [8].  Seed is borne in two rows in each locule [19].

Pinnate tansymustard has been described as a seedbanker in desert
grassland communities of New Mexico [15].  Seed stored in the soil
apparently germinates in greatest numbers either in the zones closest to
or most distant from broom snakeweed (Gutierrezia sarothrae) plants
[15].  Precise reasons for this seedling distribution have not been
determined.  The broom snakeweed plants may alter the soil environment
to favor the growth of pinnate tansymustard, or these shrubs may trap
the seeds which then accumulate and germinate near the base [15].  

The seed of pinnate tansymustard is mucilaginous when wet, which may
facilitate dispersal by animals or increase adherence to soil particles
[9].


SITE CHARACTERISTICS : 
Pinnate tansymustard is a widespread weedy species that grows on a
variety of sites.  It occurs in waste places, disturbed areas, plains,
dry hillsides, prairies, open woods, and along streambanks [4,18].
Pinnate tansymustard grows most commonly along ditches, roadsides, or on
other disturbed, open sites where mineral soil has been exposed [20].
In parts of western Utah, it is particularly common in areas which have
been subjected to high levels of rodent disturbance [7].

Although it is most abundant in arid and semiarid regions on dry or
sandy soil, pinnate tansymustard also grows on rich, moist soils in
mountainous areas [20].  It is common on disturbed soils [18,20].
Pinnate tansymustard can grow on a wide variety of soils, ranging from
gravel to dense clay [3].  Optimum soil depth is estimated to be 10 to
20 inches (25.4-50.8 cm) [3].

Elevational ranges for several western states follow [3,20]:
     
        from 3,500 to 11,900 feet (1,068-3,630 m) in CO
        less than 5,500 feet (1,371 m) in MT
        from 2,000 to 10,600 feet (610-3,233 m) in UT
        from 3,800 to 8,700 feet (1,159-2,654 m) in WY
     


SUCCESSIONAL STATUS : 
Obligate Initial Community Species

Pinnate tansymustard quickly invades disturbed areas with exposed
mineral soil and reduced plant cover.  It is characteristic of early
seral communities and competes poorly with perennial grasses and forbs
in later seral stages. It is sometimes found, however, in partial shade
under aspen or other trees [20].


SEASONAL DEVELOPMENT : 
In many areas, pinnate tansymustard is one of the first spring annuals
to appear [18].  Flowering occurs from March through August, depending
on geographic location [19].

Related categories for Species: Descurainia pinnata | Pinnate Tansymustard