Fremont Cottonwood
Family Salicaceae (poplar)
Populus fremontii

Cottonwoods are common trees found in local creeks within Alameda County.  The deciduous leaves are spade-shaped and become golden in fall.  Wind blowing through the trees sounds like running water.  Male and female flowers are borne on separate trees.  The female tree has cottony seeds that are dispersed by the wind that  blooms March to April. This tree is well known for its ability to grow quickly with heights up to  35 meters.  

Arroyo Willow
Family Salicaceae (willow)
Salix lasiolepis

This native tree is found  in the wet soils along waterbeds in valleys, foothills and mountains.  It is also known as a white willow because it has light colored bark and leaves with whitish lower surfaces.  Some varieties of willow bark were used by Native Americans to help reduce fever and pain.  The leaves are simple, about five inches long, irregularly lancolate, and have entire rolled-under margins.    Arroyo Willows can reach as high as 10 meters.   It produces yellow flowers during the spring that grow on stems in bunches called catkins.  Willows are found growing in close proximity to the water’s edge.  Birds and other animals use these trees as nesting and feeding places.

Red Willow 
Family Salicaceae (willow)
Salix laevigata

Red willow is a medium-sized deciduous tree that always grows near water.  The bark of mature trees is dark and rough; young twigs may be red to yellow-brown.  The narrow leaves are green and shiny above, whitish below, and usually widest below the middle.  Male and female flowers are borne on separate plants and appear soon after the leaves in early spring. The tiny seed produced by the female catkin has a cottony “fluff” and may be carried a great distance by the wind.  Because all willows root easily and grow quickly, they have potential for holding soil on steep slopes.  The flexible willow shoots were used by the Ohlone Indians to make baskets and huts. Willow bark contains salicin, which our bodies convert to salicylic acid, the active pain-relieving ingredient in aspirin.

Sandbar Willow 
Family Salicaceae (willow)
Salix exigua

New branches are grayish, and  leaves have a furry feeling.  Leaves are very narrow compared to other willows in the area.  The trees grow 2-4 meters. The catkins are borne on separate male and female trees about 1-4 cm in length bloom  March to May.   

Yellow Willow
Family Salicaceae (willow)
Salix lutea

A deciduous shrub or rarely small tree.  This willow is common in wet places along streams in higher elevations.  It takes the form of clustered shrubs that grows to 2-5 meters high with yellowish to brownish twigs. The male and female catkins  are 4-8 cm long, appearing before leaves, and are on separate trees.  Seeds have a cottony down which allow them to float for large distances.  

Big-leaf Maple
Family Aceraceae (maple)
Acer macrophyllum

Maples are easily recognized by their large 3 to 5 palmately lobed deciduous leaves that are arranged opposite to each other.  The yellowish green flowers appear after the leaves come out in spring. Flowers are small, yellow, born in long racemes. The double winged fruits, resembling helicopter blades, are called samaras. 

Coast Live Oak 
Family Fagaceae (beech)
Quercus agrifolia

Coast live oak is an evergreen tree which grows to 10-25 meters tall.  It has a broad, dense crown and spreading branches.  The mature bark is gray and shallowly furrowed.  Leaves are oblong to oval, cupped with toothed margins.  Clusters of rusty hairs may be seen  on the veins on the back of the leaf.    Acorns are narrowly conical and mature in one year.  Although coast live oak is often a component of riparian California  woodlands, it typically occurs on wooded and grassy slopes.  The Ohlone Indians leached acorns in water to remove the bitter tannin before preparing breads, soups and porridges.

White Alder
Family Betulaceae (birch)
Alnus rhombifolia   

Alders grow at the immediate edge of perennial streams and are indicators of a permanently high water table.  White alder has deciduous, hairless, flat leaves with toothed margins that are not rolled under.  The male and female flowers are borne in separate catkins on the same tree.  The woody female catkin resembles a small pine cone, and is often gold-plated and used as jewelry.  Young alder shoots were used to make arrows.  Dry, rotted alder wood was used along with willow bark as a poultice on wounds.  Alder roots produce a red dye and were used to make caps and trinket baskets.  Alders have nitrogen-fixing bacteria on nodules on their roots, enabling them to convert atmospheric nitrogen into nitrates and allowing them to grow on poor soils.  As alder leaves decompose, they enrich the soil and make it more acidic, preparing the land for colonization by other tree species.

Western Sycamore
Family Platanaceae (sycamore)
Platanus racemosa

Western sycamore grows along creek beds.  It is a large deciduous tree with heavy twisted branches.  Its characteristic peeling bark is smooth and ashy-white with greenish-gray and tan patches.  The broad leaves are light green above and paler and rusty-hairy below.  The fruits are contained in small bristly “button-balls” borne in clusters on the flower stalk.    It is a food plant for western Tiger Swallowtail. 

California Bay Laurel
Family Lauraceae (laurel)
Umbellularia californica

The evergreen bay tree has simple leathery lance-shaped leaves.  When crushed, the pungent leaves smell like bay rum.   Bay leaves are used to season stews and sauces, and placed on pantry shelves to discourage insect pests.  Clusters of small fragrant yellow flowers appear in December.  The fruit resembles a small avocado and turns purplish when mature.  The heavy, fine-grained laurel wood and burls are used to make plates, bowls, novelties and furniture and are often sold as pepperwood or myrtle.

Northern Black Walnut 
Family Juglandaceae (walnut)
Juglans californica var. hindsii

Leaves are pinnately compound with 11 or more leaflets per leaf.  During the fall the shiny, resinous green leaves turn soft shades of yellow.  The black walnut contains a rich, oily nutmeat, but the thick shells make it difficult to crack.  They are seldom cultivates, but serves as a rootstock onto which the English walnut is grafted. 

Western Redbud
Family Fabaceae (pea)
Cercis occidentalis

Flower is very showy, light to dark pink in color, ½ inch long, appearing in clusters in March to May before the leaves. Bark is dark in color,  smooth, later scaly with faint ridges. Fruits are flattened, dry, brown, pea-like pods, 2 to 4 inches long.  The flat, elliptical, brown seeds ¼ inch long. Maturing in July to August.

Blue Elderberry
Family Caprifoliaceae (honeysuckle)
Sambucus mexicana

Blue elderberry prefers canyon bottoms where water is available in summer, but also grows on dry hillsides. Elderberries often start as multi-trunked shrubs that mature into small trees.  The deciduous leaves are compound.  The blue berries are eaten by wildlife and were dried for later use by the Ohlones.  Early Californians made jam and wine from the berries.  The creamy flat-topped flower clusters can be dipped in pancake batter and fried.  Elderberry stems have a soft white central pith that can be removed, leaving a hollow tube that serves as a flute, clapper, or gambling stick.