Vernal Pools

Vernal Pool

Vernal pools are contained, natural depressions that lack an above ground outlet or inlet. Covered by shallow water for variable amounts of time, particularly during the winter and spring, vernal pools are home to many plants and animals that are unable to survive anywhere else. The fauna and flora of this miniature ecosystem must be able to cope with extremes – wet, soggy winters and parched summers.

These ephemeral bodies of water and wet ground are called vernal pools because they are at their peak in the spring (vernal = spring). As environmental conditions vary the pools can change (size, shape, water depth etc.) from year to year. With changing seasons and moisture the plants and animals also fluctuate.

The underlying soil is important in the creation of vernal pools. Usually hardpan, a dense layer of compacted soil or hardened minerals, is found under the uppermost layer of soil below vernal pools. Impervious to water, the hardpan prevents rain and snow melt from percolating into the soil. There are many different types of hardpan. In the arid soils of northeastern California where we live (Modoc County), hardpan is often a dense matrix of  calcium carbonate deposits. I can vouch that it is almost impossible to push a shovel through hardpan.

Without fish to eat their eggs or their young, certain salamanders and lizards have adapted to and thrive in this variable environment. Most of the plants, at least in our area, growing in vernal pools are small. However, the enormous number of their tiny flowers often turn a vernal pool white or purple in the spring.

Popcorn Flower

Popcorn flowers (Plagiobothrys sp.) are one of the many wildflowers adapted to vernal pools. These plants with small white flowers formed of five petals fused into a short white tube and a yellow eye belong to a genus that is taxonomically complex. There are over 41 species of popcorn flowers in California alone. These plants, members of the borage or forget-me-not family,  are identified on the most subtle of traits, such as the scar on the almost microscopic nutlet or seed.

Popcorn Flower

These specimens, found and photographed in a vernal pool in a meadow near Ash Creek (Lassen County CA) have linear to lance shaped leaves and are hairy overall. The flowers are on one side of a coiled stalk. I think they may be either Scouler’s popcorn flower (P. scouleri) or a downy (also called soft) popcorn flower (P. mollis). I am not certain. Both species are native to California.

Get down on the ground, eye level with these tiny vernal pool wildflowers – they are beautiful!

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5 Responses to Vernal Pools

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  4. Lin says:

    Very interesting !!!

    Do you have a book you would recommend as ‘best’ for Modoc County wildflowers? If so, I’d be interested in the title and author.

    • gingkochris says:

      Tough question! I have many reference books that I use, and wish I had more. One book that covers the flowers of our area, but is not specific to Modoc, is “Sagebrush Country” by Ronald J. Taylor and Rolf W. Valum. This is an old book (copyright 1974), although I believe there is a newer edition. The pictures are decent and it only covers wildflowers that can be found on the sagebrush steppe. One can page through the pictures and often identify local plants without resorting to keys. It is a place to start.

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