California’s Vernal Pools

The name 'vernal' means spring, and these pools are water collections that appear only in winter and early spring because of rainfall. Vernal pools form when winter rainwater collects above a hardpan clay layer just below the topsoil. As temperatures increase later in winter, many wildflowers begin to bloom, sometimes creating large patches of color. Later in spring, these pools usually evaporate completely before summer.

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At the end of April, the vernal pools dry up, turning the area brown from lack of water. Sheep and goats are brought in to graze on the dried grass as a precaution to prevent wildfires. This doesn’t impact the flower show the following year. It helps reduce invasive species and promotes native plants.

There are three phases: Wet Phase (winter), Flower Phase (spring), and Dry Phase (summer and fall). The flower display continuously varies from late January to late April.

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Below are a few interesting vernal pools.

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We even have a vernal pool here in Lincoln near Wilson Park (off East Joiner Parkway), although it hasn't been maintained for a few years (GPS 38.847323, -121.282929).

 

Jepson Prairie Preserve, Solano County

Logistics: 60 miles from SCLH. No elevation gain. Dirt pathway. Free any time. Fee for weekend docent tours. Season Feb-early May. Toilet Feb-early May.

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The best-managed vernal pool in our area is Jepson Prairie Preserve, about 10 miles south of Dixon (GPS 38.275450, -121.824815).

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You’ll see migratory and wading birds, along with hundreds of plant species, including 15 that are rare and endangered.

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Jepson Prairie docents offer tours every Saturday and Sunday during the spring months. A handbook with photos of wildflowers and detailed site information is available.

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A part of Jepson Prairie Preserve is open to visitors free of charge. Occasionally, large planes from Travis Air Force Base training exercises fly low overhead.

 

North Table Mountain Ecological Reserve, north of Oroville.

Logistics: 60 miles from SCLH, with a 200 ft elevation gain. Dirt pathway that is difficult and muddy. Fee applies using Lands Pass. Season: January-May. Toilets available.

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These are basalt flow vernal pools formed from basalt lava. See large fields of monkeyflowers, lupine, owl's clover, goldfields, and more.

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The best time to visit is from late February to early April. A daily or yearly CDFW Lands Pass is required (Annual Lands Pass costs $33.48 in 2026).  (GPS 39.5959, -121.5417). Walking is on a dirt path and can be challenging.

 

Phoenix Park Vernal Pools in Fair Oaks Recreation & Park District.

https://ca-fairoaksparksandrec.civicplus.com/DocumentCenter/View/281/Vernal-Pools-Brochure-PDF?bidId=

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Logistics: 20 miles from SCLH. No elevation gain. Dirt pathway, easy walking. Free.

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This small vernal pool hosts many interesting wildflowers.

 

To reach there, in Fair Oaks, drive south on Hazel Avenue, turn left onto Sunset, then right onto Maya Street. Next, turn left into the parking lot, where the vernal pools start at the southeast corner. (GPS 38.651752, -121.218458)

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Vina Plains Preserve, Lassen Foothills area

Logistics: 90 miles from SCLH. No elevation gain. No designated pathway, uneven walking through fields. No facilities. Docent. Free.

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This 4,600-acre site in Tehama County is fenced off, and the public can visit only during docent-led tours each spring. The gate is located at the intersection of Haille Road and Route 99 north of Chico, (GPS 39.889874, -121.984872).