Botany Blueprint: The California Flannel Bush

Specimen #8: California flannel bush Fremontodendron californicum

classic native species, the California flannel bush (Fremontodendron californicum) has perfected an environmentally-specific survival strategy. The bush is a long-time denizen of the chaparral; it knows the neighbors, the weather, and how to manage both. As such, the plant discourages anyone who attempts to reorient it elsewhere. One roving horticulturist described his bedevilment with species’ pointed seed cases way back in the March, 1882 issue of The Gardener’s Monthly and Horticulturist:

“Ah, the torments I have endured in gathering Fremontia seed! How they sting — the villainous things! You become more reckless: the back of your hand is covered with their little prickling points … I would almost as soon be rolled in a nest of ants. And to cap the climax, one or two get down the back of my neck, leaving a long stinging trail as they roll over and over on their long journey to my waist … My belief is that the first Fremontia was white. A prehistoric collector came along hunting for seed, began gathering; and the more hegathered, the hotter his temper got, until finally, the sulphurous fumes of his cursing became encrusted on the flowers so deeply and indelibly, that their color was changed and their progeny has retained it to this day.”

The author concludes: “I doubt if one could conscientiously remain long a deacon of the church and be a collector of Fremontia seed at the same time.”

The torment indeed. As the deacon discovered, “flannel” is a euphemism. Despite a velvety sheen, the plant’s leaves and stem are sharp and bristly. Not surprisingly, this protective covering is most severe on the seed cases.  The tiny hairs are stiff and unyielding. This sharp, stellate cloak is a painful deterrent to any hungry forager, and guards the seeds as they mature. At this point, however, it’s a different survival game.

As the seed case splits open, small black seeds tumble from the inner chambers. They settle on the ground, and they wait. For a fire, actually. The flannel bush is a “fire-following species,” which means it thrives after a burn. But this opportunism has a catch. The seeds are borne with a smooth pericarp which is not permeable by water. Flourishing as it does after a fire, the flannel bush in fact requires intense heat to “scarify” its seeds, a process that penetrates the skin and allows germination.

But what of the seeds until then? The California chaparral is teeming with indiscriminately hungry rodents, quick to consume the seeds before the next fire. And so the flannel bush endows its seeds with a second mechanism, a meanwhile strategy that manages their safe dormancy. Each seed is equipped with an elaiosome, a nutrient-rich appendage that actually encourages consumption. Seem ill-advised? It’s not. The tasty “EAT ME” a billboard is projected to one harvester in particular — ants. In a lovely case of mutualism, the insects carry the seeds back to their nests, consume the elaiosome, and discard the unharmed seeds. While this gesture doesn’t achieve the aforementioned scarification, it has provided the seeds with a relatively safe lair to lay in wait. And, now relieved of the elaiosome advertisement, the seeds are far less appealing to rodents rummaging about in the underground colonies.

Certainly, Fremontodendron seeds are both tough and clever – admirable traits for any plant or person. What of their design then?  Bearing classic five-pointed flowers, the seed cases — especially when open — could be mistaken for dead blossoms. This is achieved, in part, because of the flower’s structure. Unlike most flowers, the flannel bush has no petals. The flared yellow saucer consists of five sepals, which, like petals, serve to protect the flower bud and attract pollinators. Unlike many petals, however, the sepals are not shed after pollination. They retain the five-pointed form and turn brown.
Remaining on the tree to protect the fruit as it develops, the papery shroud is a dried vestige of the golden blossom – and a nice continuity of form.

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