BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Salix lasiandra | Pacific Willow 



GENERAL BOTANICAL CHARACTERISTICS : 
Pacific willow is larger than most other willows, reaching 20 to 60 feet
(6-18 m) in height at maturity [7].  Main stems reach 2.5 to 7.5 inches
(10-30 cm) in diameter [8], with very brittle wood [2].  In Montana and
Idaho Pacific willow reaches tree size at lower elevations but is found
as a short, several-stemmed shrub at higher elevations [8,18].
Staminate and pistillate flowers occur on separate plants in catkins.
Staminate and pistillate catkin lengths vary greatly, ranging from
0.6-2.7 inches (1.5-7 cm) for staminate catkins, and 0.8-2.7 inches (2-7
cm) for pistillate catkins [6,8,31,45].  The fruit is a glabrous capsule
0.15-0.3 inch (4-8 mm) long and turn from green to yellowish at maturity
[6,7].

Due to their morphological similarities, Pacific willow may be mistaken
or confused with peachleaf willow (Salix amygdaloides).  Differences in
their bud scales may be used to distinguish them [18].  Pacific willow
has bud scales without free overlapping margins and are rounded at the
tip, while peachleaf willow has bud scales with free overlapping
margins, and are pointed at the tip.  

Characteristics used to distinguish varieties include [1,7]:

var. caudata - leaves nonglaucous beneath
var. lancifolia - leaves glaucous beneath, branchlets densely pubescent
var. lasiandra - leaves glaucous beneath, branchlets glabrous
var. recomponens - leaves green beneath, branchlets pubescent


RAUNKIAER LIFE FORM : 
   Undisturbed State:  Mesophanerophyte
   Undisturbed State:  Microphanerophyte
   Undisturbed State:  Nanophanerophyte


REGENERATION PROCESSES : 
The dispersal of thousands of small windblown seeds is Pacific willow's
primary mode of reproduction.  It can also reproduce vegetatively.
Broken pieces of stem are transported and deposited on moist alluvium by
floodwaters, and later sprout [2].  Pacific willow has very brittle
branches, making this form of reproduction important in initial
colonization of some disturbed areas, but seeding still seems to be more
important [47].  Pacific willow is unable to produce sucker shoots from
lateral roots but will probably resprout from its root crown or stem
base following fire or cutting [2,16,47.

Plants are dioecious.  After fertilization, a capsule develops which
eventually splits open during spring or summer, dispersing numerous tiny
seeds [7].  Seeds are transported by wind and water.  The seeds are not
dormant and germinate rapidly, usually within 12 to 24 hours of
dispersal if a moist seedbed is reached [10].  The seeds contain
significant amounts of chlorophyll, and photosynthesis generally occurs
as soon as the seed is moistened.  Germination rates increase with
increased amounts of light [10].


SITE CHARACTERISTICS : 
Pacific willow is typically found at low to mid elevations and
immediately adjacent to a stream's or river's edge [8,17,18,].  Sites
typically have a high water table year-round.

Soils:  Soils are normally coarse-textured alluvial deposits of sand or
gravel [8,17,18] but textures range from sandy to clayey.

Associates:  In the Rocky Mountains Pacific willow is commonly found
with black cottonwood, yellow willow (Salix lutea), sandbar willow (S.
exugua), Woods rose, and redosier dogwood (Cornus sericea) at lower
elevations [8,18].  At middle elevations it is commonly found with Booth
willow (Salix boothii), Drummond willow (S. drummondiana), and thinleaf
alder (Alnus incana ssp. tenuifolia) [8,18].

Elevation:  Elevational ranges for several western states are given
below [1,18,31,45]:
 
        below 8,000 feet (2,438 m) in CA
        below 6,500 feet (1,980 m) in east central ID
        from 3,000 to 5,400 feet (914-1,646 m) in sw MT
        from 5,000 to 7,000 feet (1,525-2,650 m) in UT 
        from 4,500 to 8,500 feet (1,372-2,590 m) in WY


SUCCESSIONAL STATUS : 
Pacific willow is a pioneer or early seral species commonly found on
fresh alluvium [2,18].  Repeated flooding allows stands to persist [18].
Stands help stabilize the sand or gravel deposit, and in the absence of
disturbance other communities of cottonwoods (Populus spp.) and willows
establish and eventually replace it [18].  In California Pacific willow
was a pioneer on mine spoils deposited along dredged streams [146].


SEASONAL DEVELOPMENT : 
Pacific willow is a deciduous tree.  Flowers in the spring appear with
the leaves.  After fruits ripen, seeds are dispersed from spring to
early summer [7].

Related categories for Species: Salix lasiandra | Pacific Willow