acorns on oak branch Eaton Canyon: Be Your Own Tour Guide

Have fun discovering the plants, geology, and some of the
animals (we hope!)
of the Eaton Canyon nature preserve. But first...

Like all good naturalists, you will always:

  • Bring plenty of water when you hike
  • Stay on the trail
  • Dispose in a trash can — or take home — every bit of trash
  • Pick up after your (leashed!) dog
  • Leave everything where you found it:

Feather, flower, rock, or bark;
leave all nature in the park.

And never feed, chase, or try to touch animals. The canyon is their home.

Let’s start by looking for the geological story:

  • steep mountainsides
    The San Gabriel Mountains are considered a very young range, pushed up from below only five to ten million years ago (40 - 50 million years AFTER the last dinosaur!). In geologic time, they have not had much time to erode, so are still very steep and angular.
Steep sides of the San Gabriel Mountains
  • many smooth rocks
    The arroyo is dry most of the time, but when it rains, fast-flowing water tosses and tumbles rocks that fell from the steep hillsides, and, over time, smooths their rough edges.
smooth rocks in riverbed
  • a large boulder
    Every few decades or so, the canyon experiences hard rain and severe flooding, since all the side canyons of the local watershed empty through here. Water is powerful, and as you can see, has delivered many large boulders far downstream.
  • a rocky, wide arroyo
    In winter rains, water from the mountains above drains through the arroyo, sometimes as a deep, rushing flood that spreads far outside its usual area. From here it flows (often underground) to the Rio Hondo River and on to the Los Angeles River and then to the ocean.
wide rocky arroyo with people standing in seasonal water
Lowe granodiorite
wilson quartz diorite
Eaton Canyon’s special rocks
You’ll only find this exact mineral composition here:
Left: Lowe Granodiorite (Dalmatian rock).
Right: Wilson quartz diorite (salt and pepper rock).
Boulder Sitting in Sun
If you see this boulder…

If it’s a warm, sunny day, feel both sides, light and dark. Do you feel a difference? Why do you think that is?

Do you know the name of these mountains?
San Gabriel Mountains

Our steep and beautiful mountains are the San Gabriel Mountains

You might also see ...
  • a fallen tree trunk.  Notice how many animals are using it for food or shelter. Is fungus helping it decompose?
  • a hole in the ground.  Large? Maybe a ground squirrel made it. Others (snakes, lizards, mice) might be using it now. Small? Maybe ants live there.
  • scat (poop, often dried).  Animal scat shows what the animal, such as coyote or fox ate (unless a dog’s owner didn’t pick up after it )
  • rocks, large and small.   Many different minerals make them up. Do you see pink or green? Shiny bits? Stripes? What else do you notice?
  • a bridge (about a mile along the trail).  Originally built in the early 1900s to transport a telescope up to Mt. Wilson
  • a road climbing up the mountainside  Also built for telescope transport; hikers use it now.

Ask yourself as you walk and learn: What are some of the reasons that, for hundreds of years, the Tongva people chose to live (at least part of the year) in this canyon?

Listen for:
  • a quail  (it sounds like it’s saying, “Chicago, Chicago”)
  • an acorn woodpecker  (sounds like a loud “waka waka!”)
  • songbirds  How many different calls do you hear?
  • running water — if there has been recent rain
Look for a few of the mammals and birds who live here:
You will have a better chance to see them if you stop and stay still and quiet.
acorn woodpecker

Acorn woodpecker
what an acorn granary this guy’s family has!

(perhaps scratching the ground for bugs & seeds)

160 different kinds of birds live in, visit, or migrate through Eaton Canyon. We hope you see many of them!

Southern California has a Mediterranean climate it gets short, wet winters and long, dry summers. As you walk, you will see how plants in the canyon have adapted to live under these conditions.

You can see most of the characteristics below at many places along the way, depending on the season. Just keep your eyes open!

Look for plants adapted for heat and sun:
  • plants with tiny leaves  Many plants in a Mediterranean climate, as exists here, must conserve water during the long, hot summers. Some of them do it by producing very small leaves, which expose less surface area to the hot sun. Some leaves are tiny, but still leaf-shaped; some get as thin as graceful needles. You will find many different examples in the canyon.
  • plants with fuzzy leaves  A light fuzz on the underside of a leaf, or even all over it, is another way a plant can hold off hot air to retain moisture.
  • plants with thick or waxy leaves…  Two more ways to hold on to moisture.
  • a tree with thick bark and dark green, waxy, cupped, prickly-edged leaves
    Live oak
    The live oak is a very important tree in Southern California. Its thick bark is resistant to fire, its small, waxy, cupped leaves resist heat, and its acorns have provided food for countless types of animals, as well as for the native people who lived here for hundreds of years.
  • tree with light, jigsaw-puzzle bark and large leaves having three sections of points. (no leaves in winter)

    This graceful tree, so green in spring and summer, is a sycamore. You will see them near water sources, which they reach with their long roots. Their large leaves are velvety soft on the underside, and hummingbirds use that soft fuzz to line their nests. Goldfinches love to feed from the hanging seed balls.

    sycamore trunk
    sycamore leaves
Don’t touch these plants, but know them

Poison Oak grows as sprouts, a bush, or a vine; turns red in the fall and drops its leaves — but is always harmful to touch!

poison oak
poison oak late summer/fall
poison oak on oak tree
poison oak

"Leaves of three; let it be"

              "It’s no joke. It’s poison oak.”

stinging nettle

Stinging nettle

Ouch!! (a spring plant; painful, but full of vitamins!)
The tips of those toothed points have a very irritating chemical that makes touching this plant extremely painful; it may even cause blisters. Stinging nettle is, however, very healthful when boiled and eaten as a vegetable. If you can get it to the cooking pot without it touching your skin, you will be rewarded with a great number of vitamins and minerals, and even protein, which is unusual to find in a green, leafy plant. (But don’t collect it here.)

yucca flower

Sharper than it looks! With or without a single, tall stalk (which grows & flowers only once). Spiky leaf fibers were used for rope, sandals, thread; roots were used as soap.

One more “don’t touch!” plant
Prickly pear cactus with flower buds
Prickly pear cactus

Prickly pear. Long spines you see;
tiny ones you don't!

cochineal insect

Cochineal insect
Actual size  cochineal insect displayed actual size.

Prickly pear can store water in its green pads. Those pads are actually the plant’s stem (where it makes sugars; most plants do that in their leaves). What would be the leaves have actually become spines; no water will be escaping from them. Animals—and people—love the fruit.

Is there white, fuzzy stuff on it? That’s the foam protection of the tiny insect called cochineal. Cochineal has been used for centuries as a red dye. Here are a couple of them, magnified many times!

It’s OK to touch and smell the following plants

(but leave other plants alone; some can hurt you or activate allergies!)

White Sage
White sage leaves

White sage is one of the fuzzy-leafed plants. Black sage (below) has darker, smaller leaves, but the same nice smell.

california bush sunsflower

All OVER the place in spring!

golden current with berries

Animals love the berries! Three-lobed leaves, not three leaflets, as poison oak has.


Because foraging mules could bloat from eating too much. Seen near the stream bed. Look for tiny veins along leaf edges.

yerba santa

has thick, serrated, fuzzy leaves (holds on to water!) Lower leaves may look dead and dry. Used by native people for many medicinal uses.


handles heat in a special way: on hot days, its darkish-green leaves turn bottom-side up, which display white, a color that reflects heat away from the leaves.

A few more plants that are fun to learn
california (flat-topped) buckwheat
california (flat-topped) buckwheat (close-up)
california (flat-topped) buckwheat (dried)

California (flat-topped) buckwheat, in bloom and with rusty autumn blossoms; note how the flower tops of each stalk end at almost the same level; thus the name “flat topped buckwheat.”

(not the hot dog kind)
larger patch of dodder
Dodder (or “witch’s hair”)

Dodder doesn’t have green chlorophyll, so can’t make its own food as other plants can. It wraps around another plant—very often flat- topped buckwheat—to suck out the nutrients. It doesn’t hurt the plant, though.

wild cucumber
wild cucumber fruit
wild cucumber seeds
wild cucumber dried fruit

Wild cucumber. NOT for salads. It may have green, prickly fruits (poison!) or dried, empty seed pods. This vine uses tiny tendrils to climb other plants to reach the sun. Look for the tendrils that help it grab on.

dried phacelia

Phacelia (fa-CEEL-ya), AKA caterpillar plant. Bees love its purple pollen! You can see the caterpillar shape even after it has dried out and looks gray/brown. Activates allergies for some.

laurel sumac

The “taco tree” (note leaf shape). Two laurel sumacs near the visitor center have large wood rat nests at their base. Also can be an allergen.

Did you come in the fall or winter?

Some plants are still busy, such as these late bloomers
(or dry-blossom-keepers)

scale broom

(tiny leaves wrap around the stem to hold moisture in.)


Even pretty when dry

For many plants, it’s berry and seed season.
hollyleaf cherry

(no fruit in some years)


Loved by winter birds.

california buckeye

Seed (toxic!). Our one tree is on the front walk.

sage seed heads

Sage seed heads hold on! (and are loved by many critters.)


Acorns that have fallen from live oaks.

dried poison oak stems

No berries; just bare. Notice how Poison oak stems (don’t touch!) look somewhat vertical

dried california sagebrush

California sagebrush smells nice when it’s dry. Scrunch a stem and see.

Four common lizards
fence lizard

(maybe doing push-ups)

alligator lizard

(sometimes has zig-zag pattern)

And our essential, rodent-controlling snakes!

(if they are not in their winter sleep)

gopher snake
gopher snake head
Gopher snake (narrow head & pointed tail)
rattlesnake head
Rattlesnake (wide head, blunt tail, rattles)

Neither snake is aggressive (and the gopher snake is harmless to humans). Both will try to flee; just give them space. People who get bitten by rattlesnakes are usually people who are fooling around with rattlesnakes! (The others have surprised them by stepping or reaching into a hidden place.)


(eats other snakes, including rattlesnakes)

These three snakes are also harmless to humans (in addition to the gopher snake).
rattlesnake's tails

Fun fact: rattlesnake’s rattle looks snapped together (inside view). The looseness of the connection is what makes the rattling noise when the tail is shaken.

A few local arthopods
jumping spider
Jumping spider
garden spider
Garden spider
darkling beetle

Darkling beetle
(stink bug)

carpenter bee

Carpenter bee



fiery skipper
Fiery skipper
cabbage white
Cabbage white
gulf fritillary
Gulf fritillary
mourning cloak
Mourning cloak
Get ready for your next visit to Eaton Canyon by checking out information about the geology,
plants, animals, and history of the canyon at:, under the “Learn” menu.
And more fun awaits under the “Children’s Activity Sheets” menu.
sticky monkeyflowers
matilija popies
showy penstemon
Sticky monkeyflowers , Matilija poppies, and Showy penstemon all say, “Come back soon!”
Eaton Canyon Nature Center Associates Seal
Photo contributors include Jeff & Wendy Photography, Chuck Haznedl,
Terry Keller, Helen Wong, Mickey Long, Mari Gavisheli, and Vadi Martirosyan