The trees in Stivers Lagoon represent a land biome that is referred to as riparian woodland.  Riparian trees require moisture, deep soil, cooler temperatures, and shade.  Muskrat Creek is a permanent, human made stream that  flows through the western part of Stivers Lagoon.  It provides  damp, cool ground that is high in organic matter that nourishes the plant residents of the nature area.

The three major trees in Stivers Lagoon are the Red Willow, Fremont Cottonwood, and the California Black Walnut.  Each has its own characteristic leaves, bark, and overall shape. 

Red Willow (Salix laevigata) is a common tree throughout the lagoon.  There are other willows that you can see at the entrance to Stivers Lagoon but red willow is mainly found within the nature trail. The leaves are usually broader near the base with short pointed tips.   The one-year branches are reddish brown. 

Willows are characteristics of a riparian habitat, which thrive on the moist soil, cooler temperatures and shade of the other vegetation. 

Fremont Cottonwood (Populus fremontii) is the largest of the trees in Stivers Lagoon.  These trees have spade like simple leaves.

Wind rustling through its leaves makes it sound as if a large river is running through the area.  Cottonwoods range from 12-35 meters in height and trunk diameter ranges from .3 to 1.5 meters.  A young cottonwood has a smooth bark, but as it ages, it has a characteristic deeply furrowed, whitish bark.   Cottonwoods bloom from March to April with a drooping catkin 4-14 cm long.  The fruit has silky hairs that resemble cotton, hence the name cottonwood.

California Black Walnut  (Juglans californica var. hindsii  is also abundant in the upper part of the riparian zone.  The arrangement and shape of the leaves are characteristic.  The nut is round and dark in color.

             LESSON.  Tree Identification - Ask students to locate the cottonwood, willow, and walnut trees in this region.  Look at the leaves and bark.  Make sure the students look at the leaf shape, bark (color and texture), arrangement of branches,  and  the overall structure of the trees.

Note:  We do not recommend bark rubbings because of the presence of poison oak.  In this area, poison oak becomes more vine like and tends to grow up the bark and onto trunks and limbs of trees.