A number of the volunteers who are participating in the post-fire plant regeneration study are doing a very good job identifying plants growing on their sites. I’ve assembled the following materials to indicate some of the plants that might be of special interest as “fire-followers.” This is a preliminary document and I hope to add materials I think might be useful as I assemble them. In the meantime, I hope that those of you with some technical knowledge of plants will find this useful. In the two tables below, the page numbers refer to Barry Breckling’s wildflower book, Spring Wildflowers of Henry W. Coe State Park . If they are in bold, that means that Barry has provided a picture. For the few where there is some descriptive material but no picture, the page reference is not in bold.

Jon Keeley has been studying the relationship between plants and seed germination in California, especially in chaparral, and the tables and list below are based on his studies. Three pertinent references of his are listed at the end for those of you who might want to see them.

Plant Species found in Henry W. Coe State Park with Seeds
that are Stimulated to Germinate by Heat Shock

Table I

There is not an absolute requirement for heat-shock to induce germination in these species but the percentage of seed that germinate after heat-shock is far higher than the percentage without heat-shock. For example, without heat treatment, only about 3 % of the seeds of Ceanothus leucodermis germinated whereas with heat treatment (a few minutes at 120º C), 64 % did in one laboratory test. For Camissonia hirtella, by contrast, the numbers were 30% without and 64 % with heat treatment.

Plant Species found in Henry W. Coe State Park with Seeds that are
Stimulated to Germinate by Incubation with Moist Charred Wood

Table II

As with heat-induced germination, smoke is not an absolute, requirement for germination with these species, but the percentage of seeds that germinate after treatment with charred wood is far greater than the percentage without the treatment. For example, only 4 % of seeds of Garrya flavescens germinated in the absence of charred wood whereas 65 % germinated after treatment. With Phacelia cicutaria, the numbers were 11 and 45 percent, respectively.

Plant Species with Seeds that are Stimulated to Germinate
by Incubation with Smoke-Treated Filter Paper

Allophyllum gilioides (Polymoniaceae), Antirrhinum kelloggii (Scrophulariaceae), Chaenactis artemisiifolia (Asteraceae), Cryptantha micrantha (Boraginaceae), Cryptantha clevelandii (Boraginaceae), Emmenenthe penduliflora (Hydrophyllaceae), Mimulus clevelandii (Scrophulariaceae), Penstemon centranthifolius (Scrophulariaceae), Salvia columbariae (Lamiaceae).

All of these species were tested for germination after exposure for only a few minutes to smoke-treated filter paper, and all showed a really dramatic increase in percent germination over water-treated controls. For example, no Emmenenthe penduliflora seeds germinated on water alone, but fully 100 % of them did when placed briefly on smoke-treated filter paper.

Question: is the factor in smoke the same as that in charred wood? However, of some 12 species tested, all but one responded to both treatments. The one that didn’t showed a relatively weak response to smoke and none to charred wood under the experimental conditions used. At present, the chemical nature of the factor(s) in smoke and charred wood that stimulate the germination of the seeds of certain species are not conclusively identified although some of the gaseous oxides of nitrogen may be at least partially responsible.

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Geophytes—plants growing from bulbs—that flower profusely after a fire

Table III

Tables I and II and the list above contain only species that have actually been experimentally tested. (Jon Keeley has been very productive!) It is very likely that there are many more species out there that respond either to smoke and/or charred wood, and to heat shock. There are almost certainly many more species that respond to one or the other of these fire-related stimuli. Only two of the above-listed species tested for the influence of smoke-treated filter paper are found in Henry W. Coe State Park (bold face above: Antirrhinum kelloggii and Emmenenthe penduliflora). However, the park has species representing all of the other genera listed, and it is possible that our park species also respond to smoke or charred wood or both. For example, Mimulus clevelandii (Scrophulariaceae) is stimulated to germinate by smoke. Volunteers have observed extraordinary numbers of flowering Mimulus douglasii (PURPLE MOUSE EARS, PURPLE MONKEY FLOWER) in several areas of the Lick burn. It seems reasonable to expect that the seeds of Mimulus douglasii are also stimulated to germinate by some factor in smoke (or charred wood). There are undoubtedly other plants out there with seeds stimulated by heat shock or smoke/charred wood. These lists are by no means complete. Finally there are bulb-based plant such as Zigadenus fremontii (Fremont’s star lily) that flower dramatically after a fire (Table III). Nothing is known about what stimulates this remarkable response. So, watch for bulb-based plants—blue dicks, Ithurial spears, serrated onion, star flower, globe lily, soap plant, etc. Are there many more than you might expect?

Family Common Names:

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