In this workshop you will learn plant taxonomy of vernal pool species. This is a three-day workshop combining laboratory and field studies of the taxonomy of vernal pool plants with a focus on difficult genera.

Vernal Pool Plant Taxonomy

April 22-24, 2024
Davis, CA
Taught by Carol Witham and Jennifer Buck-Diaz

CNPS Members $550 / Non-Members $600
Capacity: 22 participants
Registration is Full



Target Audience: Professional botanists, ecologists, wetland scientists, land managers, resource specialists, and conservationists. Participants should have an initial understanding of plant terminology and basic plant identification skills.

Description: This is a three-day workshop combining laboratory and field studies of the taxonomy of vernal pool plants with a focus on difficult genera. This course focuses on plant taxonomy of vernal pool species. 

California vernal pools have been called a spatially-stable, pedo-climax community dominated by dwarfish annual plant species. There are about 200 plants known to occur in vernal pools of which half are endemic to this ecosystem. Most of the plants are small. There is a dizzying array of somewhat cryptic species in several of the endemic genera such as Lasthenia, Eryngium, and Plagiobothrys. These genera also contain rare, threatened, and endangered species.

We will visit claypan vernal pools of the basin and basin-rim formations in Yolo and Solano Counties and hardpans of both low and high alluvial terraces in Sacramento County. Sites have been chosen to maximize exposure to a wide range of plant species including several rare taxa. If all goes well, we will visit pools at Wilcox Ranch, Tule Ranch, Sacramento Prairie Vernal Pool Preserve, Rancho Seco, and possibly Howard Ranch (the order in which we visit them may vary with the weather).  

Participants will learn:

  • The higher level knowledge required to confidently identify vernal pool plants both in the laboratory and in the field.
  • Characters used to distinguish species beyond those used in the typical dichotomous plant key.
  • Field identification skills to increase efficiency and effectiveness at vernal pool vegetation assessments, floristic surveys, and rare plant surveys.

Schedule & Locale

Monday, April 22

Meet at Esau Hall at UC Davis. Indoor lecture, classroom setting.

8:00 am
Welcome and Introductions

9:00 am
Utilize the extensive UC Davis herbarium collection to cover the various characteristics that can be used to identify species in some of the more complex genera

12:00 pm
Lunch Break (please bring your own lunch and water; some concessions are available nearby on campus)

1:00 pm
Continued work in the classroom, optional herbarium tour

5:00 pm
Wrap up discussion

5:30 pm
Break for the day

Tuesday, April 23

We will meet at the Mace parkandride in Davis at 8:00 am and carpool to field sites. The full day will be spent in the field honing sight recognition of common vernal pool species including techniques for field identification of species within some of the more complex groups.  

8:00 am
Meet at the Mace parkandride in Davis and carpool to field sites

12:00 pm
Lunch in the field (please bring your own lunch and water)

1:00 pm
Continued field study

5:00 pm
Break for the day

Wednesday, April 24

We will determine the meeting location for day 3 during the classroom session on day 1. From the designated location we will carpool to field sites, continuing exercises from day 2.  

8:00 am
Meet at the designated location and carpool to field sites

12:00 pm
Lunch in the field (please bring your own lunch and water)

1:00 pm
Continued field study

4:00 pm
Q&A; course evaluations

5:00 pm
Workshop concludes

Schedule subject to change.

Venue: On day 1, this workshop will be held at Esau Hall on the UC Davis Campus (note that nearby visitor permit parking is $16 for the day). On days 2 and 3, we will meet at designated park-and-ride locations and carpool to vernal pools in Sacramento, Solano, and Yolo Counties. More details will be provided to registered participants about a week before the workshop. Participants are responsible for finding their own overnight lodging.

Materials & Requirements

Please bring...

  • Hand lens 
  • Transparent tape (regular and double-sided) 
  • Spiral bound 3×5” or 4×6” index cards (to make mini field herbaria) 
  • Rubber band(s) to secure the index card mini herbaria  
  • Clipboard 
  • Field notebook and pencil 
  • Sturdy shoes or boots, hat & field clothing appropriate for the weather and conditions (e.g. protection from poison oak, rain, sun, heat/cold, insects, etc.) 
  • Packable lunches, plenty of water, and snacks for all 3 days

Materials Provided: CNPS will provide handouts and numerous illustrated keys.

Physical Requirements: Participants should be physically able to walk up to 3 miles at a time along uneven paths and trails, and remain outside for up to 9 hours at a time. This workshop will be held rain or shine. We will spend approximately 66% of the time in the field. 

About the Instructors

Carol Witham

Carol Witham has been studying vernal pool ecosystems for over 30 years. She is a recognized expert in the rare plants and animals of vernal pools. She regularly presents lectures about vernal pool ecology. Carol was the editor of Ecology, Conservation, and Management of Vernal Pool Ecosystems (1998), co-editor of Jepson Prairie Preserve Handbook, 3rd Edition (2012), and author of A Field Guide to Vernal Pools of Mather Field, Sacramento County (2006).

Jennifer Buck-Diaz

Jennifer Buck-Diaz is a vegetation ecologist and botanist with the CNPS Vegetation Program. She brings to CNPS extensive work experience with different plant communities across the western United States. Prior to joining CNPS, Jennifer worked as an ecologist with The Nature Conservancy at the Cosumnes River Preserve. She holds a B.S. and M.S. in Plant Biology from the University of California, Davis.

Scholarships Available

CNPS is committed to reducing barriers and broadening participation in our workshops. We are offering financial support opportunities for students, early professionals, or anyone who may not otherwise be able to attend. This scholarship will cover the cost of one CNPS plant science workshop.

The scholarship form is due six weeks before the workshop date that you would like to attend. You will be notified within four weeks of the workshop date about the financial aid determination. Please click here to fill out the form to be considered as a potential recipient of a workshop scholarship.


 The CNPS Vernal Pool Plant Taxonomy Workshop is full. Please fill out this form to be added to the waitlist.

Before registering, please review the workshop waiver and photo release, plus our full workshop cancellation policy and participant expectations. The last day to cancel your registration for this workshop and receive any refund (less the cancellation fee) is Monday, April 8, 2024. For other ways to register, please see our registration & payment policy.

Did you know CNPS members get discounts on workshops? If you’re not a current member, you can join or renew now before completing the registration form below to qualify for special members-only rates!