BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Salix nigra | Black Willow 



GENERAL BOTANICAL CHARACTERISTICS : 
Black willow is a small (sometimes shrublike) to large, short-lived,
deciduous tree [3,5,8,27,29].  It is fast growing and may reach maturity
within 30 years [8,17].  This tree usually obtains a height of 66 feet
(20 m) but can grow up to 138 feet (42 m) on some sites [8].  The
massive trunks are usually leaning and are often divided.  The bark is
thick and deeply divided into furrows separating thick, scaly ridges.
The crown is broad and open with stout branches [27].  Twigs are slender
and easily detached [8].  Leaf blades are variable in size, the larger
to 4.7 inches (12 cm) long.  Black willow roots are shallow and
laterally extensive [5,39].


RAUNKIAER LIFE FORM : 
   Phanerophyte (mesophanerophyte)
   Phanerophyte (microphanerophyte)
   Phanerophyte (nanophanerophyte)


REGENERATION PROCESSES : 
Sexual reproduction:  Black willows start producing seed when they are
about 10 years old [4,5].  Optimum seed-bearing age is from 25 to 75
years.  The trees have good seed crops almost every year. producing an
average of 2.3 million seeds per pound (5 million/kg).  Seeds ripen 45
to 60 days after catkins are pollinated by insects or wind.  As the
seeds fall, the long silky hairs act as wings to carry the seeds long
distances.  The seeds are also disseminated by water [5].

Seeds are not dormant.  Viability is greatly reduced by only a few days
of dry conditions.  Germination is epigeal, and germination capacity is
usually high.  Very moist bare mineral soil is best for germination and
early development [5,14,28].  Once seedlings are established, full light
promotes vigorous growth.  Seedlings grow rapidly in a favorable
environment, often exceeding 4 feet (1.2 m) in the first year.  Low
ground cover competition and shade, however, greatly hampers growth
[28].

Vegetative reproduction:  Root stocks of very young black willow trees
sprout prolifically.  Propagation by cutting is the usual method of
artifical regeneration [5,39].


SITE CHARACTERISTICS : 
Black willow is most common on river margins where it occupies the
lower, wetter, and often less sandy sites.  It is also common in swamps,
sloughs, swales, gullies, and drainage ditches, growing anywhere light
and moisture conditions are favorable [5].  It flourishes at or slightly
below water level and is not appreciably damaged by flooding and silting
[5,16].  On a flooded site in southern Illinois, black willow survived
32 or more days of complete inundation [16].  Black willow, however, is
not drought tolerant.  Whole stands may die out when water tables lower
and soil drys up [39].

Soils:  Black willow grows on a variety of soils but develops best in
fine silt or clay in relatively stagnant water.  It thrives in saturated
or poorly drained soil from which other hardwoods are excluded [6,24].
Black willow is commonly found in moderately acidic (lower pH limit is
4.5) to near neutral soils [5].

Climate:  Black willow grows best in climates characterized by an
average annual rainfall of 51 inches (130 cm), with approximately 20
inches (51 cm) falling from April through August.  The average maximum
temperature across its range is 93 degrees Fahrenheit (34 deg C) in the
summer and 59 degrees Fahrenheit (15 deg C) in the winter [5].

Plant associates:  Black willow is commonly associated with the
following species:  eastern cottonwood, red maple (Acer rubrum), black
spruce (Picea mariana), river birch (Betula nigra), American sycamore
(Platanus occidentalis), boxelder (Acer negundo), red mulberry (Morus
rubra), swamp privet (Forestiera acuminata), buttonbush (Cephalanthus
occidentalis), water elm (Planera aquatica), and American elm (Ulmus
americana) [5,39].


SUCCESSIONAL STATUS : 
Black willow is a pioneer or early seral species commonly found along
the edges of rivers and streams, mud flats, and floodplains.  This tree
is very shade intolerant and usually grows in dense, even-aged stands.
Black willow stands periodically stagnate and are eventually replaced by
more shade-tolerant trees such as American elm, sycamore (Platanus
spp.), ash (Fraxinus spp.), boxelder, and sweet gum (Liquidambar
styraciflua) [5,14,32,34,41].


SEASONAL DEVELOPMENT : 
Black willow flowering begins in February in the southern portion of its
range and extends through late June at the northern limits.  The catkins
usually appear at the time of or immediately preceding leaf emergence
[5,39].  Seeds ripen and fall in April to July [39].

Related categories for Species: Salix nigra | Black Willow