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Biology LibreTexts

25.1: Key to Common Local Tree Genera (Written for Humboldt County, California)

  • Page ID
  • 1a. Foliage is broadleaved--composed of a flat blade, often with a distinct central vein....2 (Hardwoods: Angiosperms)

    1b. Foliage is not leaf-like--composed needles or small, thick, scale-like leaves... 9 (Softwoods: Conifers)


    2a. Edges of the leaves are smooth (the leaf margin is entire) ...... 3 

    2b. Edges of the leaves are toothed or lobed …………………….... 6 


    3a. Younger bark is reddish and peeling, leaves are relatively tough and approximate a rounded oval. Produces clusters of bell-shaped flowers and red berries …………………………...... 4 

    3b. Bark is not as above; leaves are long and pointed (lanceolate) ................. 5 


    4a. Leaves are large and shiny, upper and lower surfaces of leaves are different in appearance. Older portions of the trunk are covered in grey, finely scaled bark. Exposed inner bark is often a pale yellow to orange. Berries are warty. Can grow to be large trees.... Pacific madrone (Arbutus menziesii)

    4b. Leaves are small and often upper and lower surfaces look the same (isofacial). Most exposed bark is dark red and smooth, often interspersed with blackened-to-grey portions lacking bark. Berries are smooth. Growth form can be creeping ground cover to large shrub/small tree... Manzanita (Arctostaphylos spp.)


    5a. Leaves have a golden underside. Fruits are nuts surrounded by spiny case...Chinquapin (Chrysolepis chrysophylla)

    5b. Leaves are green on both sides. When crushed or cut, leaves have a strong, spicy smell. Not mycorrhizal. Often host wood-decay species, such as Ganoderma brownii...California bay laurel (Umbellularia californica)


    6a. Leaves palm-shaped, deeply dissected, and emerging opposite from each other on the branch.... Maple (Acer spp. In our area, most likely big leaf maple, Acer macrophyllum)

    6b. Leaves are not as above ... 7


    7a. Leaf edge has larger teeth, the edges of which are lined with smaller teeth (doubly serrate). Bark is smooth, often covered with lichens. Produces clusters of small, woody "cones" (each about the size of an olive). Tree is growing near water or in a low area where water might collect seasonally...Red alder (Alnus rubra)* Note: If leaf edges are smooth and the tree produces berries, it is Cascara!

    7b. Leaf edge has a single row of teeth or lobes. Bark is usually grey to brown and furrowed (though can be smooth when young). Fruit is an acorn...8


    8a. Leaf edge has a single row of teeth. Entire underside of leaf is covered in tan fuzz. Acorn cups have scales that scoop outward, giving them a fuzzy or hairy appearance... Tanoak (Notholithocarpus densiflorus)

    8b. Leaf edges are lobed (sometimes lobes end in sharp points). Acorn cups are formed of tightly overlapping scales that do not scoop outward... True oaks (Quercus spp.)


    9a. Leaves needle-like: rounded, long, and emerging in bundles (fascicles). Cones are woody and tough, not easily broken apart... Pines (Pinus spp.) 

    9b. Leaves in flattened sprays. scale-like, or emerging around the branch, like a bottlebrush... 10


    10a. Leaves flattened with a distinct upper and lower surface, the lower surface often silvery. Emerging from either side of the branch in a single plane (in some species, may be pointing upward, but not oriented all the way around the branch like a bottlebrush). Foliage not sharp.....11

    10b. Leaves scale-like or leaves might be as above, but emerging around the branch from all sides, like a bottlebrush...14


    11a. Leaves fall to the ground in feather-like branchlets. Cones are small (smaller than a grape) and rounded, forming distinct segments. Bark is reddish and fibrous, can form incredibly tall trees... Coast redwood (Sequoia sempervirens)

    11b. Leaves fall to the ground as individual needles. Cones and bark not as above...12


    12a. Leaves are all similar in length, usually around 2-3 cm. Cones are not often found because they deteriorate quickly. When present, cones sit upright on top of branches....True firs (Abies spp.)

    12b. Leaves with two distinctly different lengths (shorter and longer).................13


    13a. Leaves are short, less than 2 cm. The leader (top) of the tree is droopy and the cones are small (about the size of a dime) with relatively large scales. Bark is greyish with shallow furrows..Hemlock (Tsuga

    13b. Leaves are all over 2 cm long. Smooth bark in younger areas of the tree, often with a pinkish cast due to organisms growing on the bark. On the coast at low elevation……...Grand Fir (Abies grandis)


    14a. Leaves as needles, emerging around the branch like a bottlebrush. Cones oval and papery (not woody)...17

    14b. Leaves scale-like. Other features not as above....15 


    15a. Leaves as tiny, overlapping scales, forming dense clusters of dark green sprays. Cones woody, globose, and composed of distinct plates (like a soccer ball). Found in coastal areas....Monterey cypress (Hesperocyparis macrocarpa)

    15b. Leaves as overlapping, awl-shaped scales that occur in flattened sprays. Other features not as above..16


    16a. Scales are elongated, forming a champagne glass shape. Cones are small and dangle from the branch. They resemble duckbills, pistachio shells, or upside down tulips. Bark is deeply furrowed and often has an orangey cast. Found more commonly in inland areas or at higher elevations in our area...Incense cedar (Calocedrus decurrens

    16b. Scales are short with a bloom of stomata on the underside (appearing as a lighter green) in the shape of a bow or set of wings. Cones are small and sit erect on the branch. They resemble a blooming rose. Bark is fibrous. Found more commonly in wet, lowland areas...Western red cedar (Thuja plicata)


    17a. Needles are sharp, cones composed of uniform overlapping scales (like a fish). Bark looks chippy, like peeling paint. On the horizon, branches angle upward. Found in coastal forests....Sitka spruce (Picea sitchensis)

    17b. Needles are soft, not sharp. Cones have bracts that emerge between the scales, often referred to as a "mouse butt" because it looks like two feet and a tail hanging out. Bark is deeply furrowed and plated....Douglas-fir (Pseudotsuga menziesii)

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