Order “Plant Communities of Marin”


Do you want to learn more about the diverse plant communities of this special county ?

Plant Communities of Marin County written by David Shuford and Irene C. Timossi and illustrated with exquisite black and white photographs of the communities and their member species, is an excellent resource. Send your check payable to CNPS for $10 per copy (shipping, handling& tax included) to:

Phyllis Faber, 212 Del Cosa Drive, Mill Valley, CA 94941

Enclosed is $____________. Please send

me ___ copies of “Plant Communities of Marin County”




Invasive Plants Threaten Biodiversity

Invasive Plants Threaten Biodiversity

Invasive plants can significantly impact many of the complex relationships in California’s beautiful and biodiverse landscape.

California is home to some of the most beautiful and biodiverse areas in the world: oak woodlands to redwood forests; serpentine and valley grasslands to alpine meadows; coastal wetlands to riparian corridors. These communities support an astonishing variety of insects, plants, and other animals in a diverse, interdependent web of life.

Carpobrotus edulis Cape iceplantCarpobrotus edulis – Cape iceplant (Vernon Smith)Unfortunately, invasive plants can significantly impact many of these complex relationships. Invasive plants such as water hyacinth (Eichhornia crassipes) blanket waterways; iceplant (Carpobrotus edulis) smothers dunes. Weeds like blue gum (Eucalyptus globulus) and Acacia spp. from Australia, African veldt grass (Erharta erecta), French broom (Genista monspessulana), pampas grass (Cortaderia spp.), and poison hemlock (Conium maculatum) invade grasslands and forests. Grasslands once comprised of native annual grasses, perennial bunchgrasses, and annual and perennial wildflowers are now dominated by annual grasses and forbs from the Mediterranean region. Roadsides are now being invaded by rampant stinkwort (Ditrichia spp.).

Invaders displace native plants and animals. They diminish forage for livestock, native fish, and wildlife. Some invasive plants consume enormous amounts of water; some block natural waterways causing flooding. Many increase wildland fuel loads, making adjacent residential neighborhoods and wild areas more fire-prone.  Erharta erecta IMG 8683Erharta erecta – African veldt grass (Vernon Smith)Our warming climate may cause invasive plants to expand into new areas posing an increasing threat to biodiversity.

How do non-native plant species get here?  International travel, shipping containers, and imports of agricultural products can spread propagules (seeds or plant parts that grow into new plants), but the greatest culprit is the horticultural trade. Gardeners find many of these invasive species attractive, providing a market for commercial growers and nurserymen to supply. Property owners and landscapers often lack information about a plant’s potential to spread outside landscaped spaces.  In the past, even landscape restoration projects used invasive plants such as cordgrass (Spartina spp.) and ice plant (Carpobrotus edulis) to control erosion quickly.

Not all non-native species are invasive, but those that are have a competitive edge for several reasons. They often lack natural predators to hold them in check.  For example, no insect in sufficient numbers and no browsers in Marin eat French broom, a shrub that continues to invade our wildlands. Many invasive species are strong colonizers, easily dominating damaged or denuded landscapes.Genista monspessulana IMG 0688cGenista monspessulana – French broom (Vernon Smith)

CNPS works with its partners Cal-IPC and Calflora to monitor and map rare and threatened plants and plant communities, identify immediate and potential threats of new invasive plants, promote restoration of native plant ecosystems, and encourage horticulturalists to use California native plants (locally sourced when available). Marin Chapter members have successfully lobbied to require 70% CA native vegetation for new developments in the recently approved update to the Housing Element (see pg. 62) of the Marin Countywide Plan.

Spartium junceum Spanish broomSpartium junceum – Spanish broom (Vernon Smith)

Ditrichia graveolens stinkwortDitrichia graveolens – stinkwort (Vernon Smith)

Mats of ice plant cover huge parts of the Point Reyes dunes. Photo: Laura Lovett

Oaks of Marin

Oaks of Marin

Text by Doreen Smith and photos by Doreen and Vernon Smith and Susan Schlosser


Quercus douglasii : blue oak

Quercus douglasii : blue oak – Photo by Vernon Smith

In Marin this species of oak is found to the North-east of the county, around Novato and Black Point. Once the California Blue oak was the most extensively found hardwood tree in the State but now regeneration has not kept up with removal and natural mortality.


Trees are 20 to 60 feet tall when mature, with trunks 2 to 4 feet in diameter.
Bark is light grey, shallowly checked and may flake.

Quercus douglasii : blue oak – Photo by Vernon Smith

Leaves are blue-green, usually shallowly lobed, about two inches long and deciduous in the fall.
Acorns mature in one year, are medium in size and are blunt-tipped in shallow warty cups.

Quercus agrifolia : coast live oak

The most common California Coast Range species of oak is also the most widely-found kind of oak in Marin. It is at home in many habitats, on hills, in valleys, in poor or good soils but not in wet places. This oak regenerates well after cutting or burning as well as from seed. Browsing animals  are deterred from eating mature growth because of the stiff and holly-like leaves.

Quercus agrifolia : coast live oak – Photo by Doreen Smith



Mature trees are squat and broad, typically 30 to 75 feet tall.
The short, thick trunk may be several feet in diameter, it usually branches low to the ground giving rise to a  wide, spreading  crown.
Evergreen leaves of medium size are dark green and shiny above, paler with axillary hairs below; the margin is characteristically spiny. Leaves are convex and cannot be flattened easily.
Acorns are medium in size, pointed at the apex, mature in one year and are borne in scaly cups.

Quercus Kelloggii : California black oak

This species of oak is widespread in Marin, usually in mixed forest and especially in sheltered ravines and on North-facing hillsides. State-wide it is found in both coastal and mountain regions. No-where is it reseeding well, perhaps due to fire-suppression conifers out-compete it in many areas.

Quercus kelloggii : California black oak – Photo by Vernon Smith


The bark is dark-colored, furrowed and checked.
Leaves are large, deciduous, up to 8 inches long and four inches wide, deeply-lobed, each lobe with 1 to 4 bristle-tipped teeth. The upper surface is bright green and glossy when mature, the leaf lower surface is paler and may be hairy.
The acorns are large, borne in scaly caps and take two years to mature.

Quercus lobata : valley oak

The tallest and largest of California oaks is most commonly found on deep fertile soils and along river-banks. The value of such sites for agriculture resulted in the removal of countless trees in the past. Where the oaks remain they are becoming senescent and as they fall they are rarely replaced by seedlings due to grazing, fires, rodents and competition from introduced plants. To maintain this species of oak we have to plant and protect young trees .


Quercus lobata : valley oak – Photo by Vernon Smith

Mature trees can be over 100 feet tall with trunks 10 to 13 feet in diameter at the base. The bark is grey, deeply ridged and grooved.
The trunk branches high to give a vase-shaped crown, the branches hang down at the ends.
The medium-sized leaves are lobed, bright green above, pale green on the undersides; they are deciduous in the fall.
Acorns mature in one year, they are medium to large, can have blunt or pointed tips and  have very warty cups.

Quercus durata : leather oak

A shrubby oak found in serpentine, usually chaparral areas in Marin. The name comes from the leathery texture of the leaves.

Quercus durata var. durata : leather oak – Photo by Vernon Smith


A shrub or small tree, up to 15 feet tall.
Scaly bark.
The leaves are greyish green, evergreen, lobed, about 1″ long, and leathery in texture.
The acorns are of medium size, tip rounded, and mature in one year. Cap has warty scales and is cup-shaped.

Quercus wislizeni : interior live oak

The most abundant and widespread oak in chaparral areas of Marin.

Quercus wislizeni var. frutescens : interior live oak


Can be a shrub or tree up to sixty feet tall.

Trunk bark is dark and furrowed.

Evergreen, shiny, leaves, dark green above, often with toothed edges.

Acorns are medium with pointed tips and cup-shaped, warty caps. Ripen the second year.

Quercus chrysolepis : canyon oak

Common oak in canyons and on rocky ridges.


Quercus chrysolepis : canyon oak – Photo by Vernon Smith

Quercus chrysolepis: canyon oak – Photo by Vernon Smith

Can occur as a large tree or a shrub with scaly, light-colored, furrowed bark.

Medium evergreen, pointed leaves, shiny and dark green above and dull below.

Acorns are egg-shaped, about 1″ long with saucer-shaped, scaly cup, taking two years to mature.

Quercus parvula var. shrevei : Shreve’s oak

Oak found in moist woodland and forest.

Quercus parvula var. shrevei : Shreve’s oak – Photo by Vernon Smith


Tree up to ninety feet tall.

Small acorns with rounded  scaly cups.


Quercus berberidifolia : scrub oak

Oak found in chaparral.

Quercus berberidifolia : scrub oak – Photo by Vernon Smith


Shrub or small tree, with gray, scaly bark.

Small evergreen oval leaves that can be shiny.

Small acorns with bowl-shaped cap with warty scales. Matures in one year.

Quercus garryana : Garry oak or Oregon oak

Oak found on rocky outcrops and drier meadows.

Quercus garryana : Oregon oak – Photo by Susan Schlosser


Shrub or small tree, with thin scaly bark.

Deciduous large oval leaves, shiny and dark green above and paler and hairy beneath.

1″ long oblong to roundish acorns with cup or saucer-shaped cap with warty scales or not. Matures in one year.

Planning for Biodiversity in the Urban Corridor

Planning for Biodiversity in the Urban Corridor

by Paul da Silva

Marin County’s 1973 General Plan has been considered visionary and largely responsible for saving most of the County from the rampant development that has caused so much damage to the native plants and their ecosystems in California. However, after 50 years a major failing has become evident; although it provided for environmental protection of the coastal recreation corridor and the central agricultural corridor, it neglected the environment of the eastern urbanized corridor.

Now, with increasing pressure to build more housing, especially in eastern Marin, state legislation has restricted the environmental challenges that can be brought against new development. However, new rules may mitigate the environmental harms of development if they include requirements for inclusion of native plantings.

Although many kinds of “subjective” challenges that were brought against developments in the past are now prohibited, localities still have the power to enforce “objective” design standards, and these can include specific requirements for native plants. Marin CNPS members took advantage of this opportunity in the recent update of the county’s Housing Element, which included “objective” designs standards in its Form-Based Code. Developers who are applying for approval based on the requirements of the Form Based Code are now required to landscape with 70% native plants.

Individual cities and towns in Marin are also updating their General Plans and design standards. The City of Larkspur is in the last stages of its work on both. The Town of San Anselmo has announced its plans to begin updating its General Plan.

Native plants flourish in the median by the Lark Theater by Laura Lovett

Wherever you live in Marin,  pay attention to what your local government is doing. Ask for the latest planning documents and check whether they mention native plants. If they do not, try to see where they might fit in, and at the next update, give public input about this.

For the county and those localities that already mention native plants in their General Plans or objective design standards, people can check on the approval processes for any new developments to see that the regulations are being followed. If enough members do this, we may soon see more native plants near in our urban corridors where most Marin residents live and work!

Join the 50th Anniversary Marin Native Plant Challenge

Join the 50th Anniversary Marin Native Plant Challenge

The Challenge

As part of our 50th Anniversary festivities, the Marin CNPS Board presents you with the following Challenge: find and photo-document 50 native plants in Marin’s glorious wildlands and be eligible for a drawing at our August 24th Celebration! Prizes may include plant-oriented books, restaurant gift certificates, and more!

The goals of the Challenge are to highlight the beauty and diversity of Marin’s native flora and to focus attention on the habitats where these especially interesting plants thrive.  We hope many will enjoy observing these plants in places both familiar and new.

How to Take Part in the Challenge

The Challenge will run from March 1 through July 31, 2024, and only plants documented within this period and within Marin County will qualify.  Choose your 50 native plants from this List of 75 species compiled by our Committee. The List includes habitat information and suggested trails to help you find the plant.

Participants will document their finds in an iNaturalist Project entitled Marin CNPS 50th Anniversary Native Plant Challenge. When you find a plant that is on the List, click on the camera icon on the iNaturalist app to take a photo. Follow the prompts to upload it into the Project.

Committee members are not eligible for the drawing, but will be taking part for fun, monitoring participants’ efforts, and cheering them on!

Need Help? Never fear! Our new field trips team is planning hikes geared to the target plants and an iNaturalist orientation to help you get started.

You can also use this PlantID.net illustrated guide to familiarize yourself with the Challenge plants before you hit the trail.

Additional useful sources to find and identify plants include

Getting Started with iNaturalist

  • Go to the App Store or Google Play to download the iNaturalist app onto your smartphone.
  • Once you have the app, click on “Sign Up” to open an account and follow the prompts.
  • Go to the Projects Tab at the bottom of the screen and start typing the name of our project (Marin CNPS 50th Anniversary Native Plant Challenge) into the search bar. Click on “Join this Project;” the project will then appear in the Projects Tab on your screen whenever you open iNaturalist.
  • You can view video tutorials on using iNaturalist.

How to Save an Illustrated PlantID.net Guide on Your Phone to Use Later Without Internet

  • On your phone, open a link to thePlantID.net illustrated guide
  • Choose “Reports” from the drop down menu below “View
  • Scroll down and select “Start Report”. This will create a PDF.
  • Tap the download icon (box with an arrow)
  • Select “Options”
  • Under Options check “Send as PDF” and “Done”
  • Scroll down the list to choose “Save to files”
  • Save
  • To view the guide, go to the “Files” app on your phone
  • Tap on the file name (it might be in a Downloads folder)