Anyone who has ever hiked with a botanist has probably been witness to the peculiar ritual of picking small pieces of plants, rubbing them between index finger and thumb, and holding the slimy product up to their noses. Like wine enthusiasts sniffing a cork, botanists rely on more than just sight to identify plants.Smell can be a very useful indicator of a specimen’s identity. Many plant species have particular odors emanating from oil glands in leaves or stems,or from glandular hairs. Some are pleasant. Some stimulate the digestive juices by reminding us of a favorite spice or herb. And some can elicit revulsion,which is especially amusing when coming from an unsuspecting family member or friend.

Many plant species found in the five mediterranean climate regions of the world are noted for having fragrant herbage. Perhaps no aroma better characterizes the vegetation of California than sage. Our state is home to many, many plants with pleasant-smelling leaves or stems-California bay (Umbellularia californica);members of the Asteraceae or sunflower family: Artemisia, Gnaphalium,Madia, Holocarpha, Centromadia; members of the Apiaceae or carrot family: Sanicula; members of the Lamiaceae or mint family: Salvia (sages),Trichostema (vinegar weed), Monardella (coyote mint, pennyroyal); members of the Rosaceae or rose family: Potentilla-to name a few.

But then there are the skunkweeds, so named for their mephitic (derived from the Latin name for the skunk genus, Mephitis) odor. These little annual herbs qualify as what is affectionately referred to as “belly plants,” These diminutive plants are easily overlooked. But when disturbed by a hiker’s shoes, many species give off a pungent skunk-like odor. The strength of the odor is really rather remarkable. It permeates the air. You don’t even have to see them to know you’ve trodden across a patch of the skunkweeds. And the similarity between this little herb and that all-too-familiar aroma ejected from the business end of a skunk is astounding.

The skunkweeds belong to the phlox family (Polemoniaceae). The family consists of approximately 320 species in 19 genera, occurring throughout the Americas,Europe, and Asia. It is characterized primarily by perennial and annual herbs,but also includes shrubs, lianas, and small trees. The only economic uses of members of the phlox family are for their value as ornamental plants,such as Phlox, Polemonium, and Gilia.

California is host to 17 native genera in the Polemoniaceae. In California, the genus Navarretia consists entirely of native species, and includes 27 species and 16 subspecies. Among these are three state- or federally-listed species, nine CNPS List 1B species (rare, threatened, or endangered in Californiaand elsewhere), and seven CNPS List 4 species (of limited distribution).Named after the Spanish physician F. Navarrete, who lived in the 1700s, theskunkweeds consist of annual, erect herbs with glandular, hairy, or puberulent foliage. There are approximately 30 species in the genus, which occurs inwestern North America, Chile, and Argentina.

Skunkweed (Navarretia squarrosa) is another of those species thatare considered common and widespread in the state, but have become rare in San Francisco. The species was first named based on collections made in the Presidio by Eschscholtz in 1824. It was once common in disturbed sites, on sandy and clayey flats, and in vernally moist depressions in the city. It was formerly found between Lobos Creek and Fort Point, on the Sunset District dunes, and around Lake Merced, Laguna Honda, Mt. Davidson, and the San Miguel Hills. The remnant populations are restricted to sandy sites in the Presidio, e.g., off Battery Caulfield Road. The range of skunkweed includes open, wet, gravelly flats and slopes below 3,000 feet from the North Coast Ranges, northern Sierra Nevada foothills, and San Francisco Bay, to the South Coast Rangesand Baja California.

Skunkweed has long-hairy, glandular stems two to twenty inches tall. The leaves are once to twice pinnately compound. The flowers of skunkweed are not unattractive. Surrounded by sharp-pointed bracts, the tubular flowers are a deep blue and occur in dense heads, much like the gilias. Skunkweedflowers from May through July.

So on your next hike, use all of your senses. Don’t disdain the habit of sniffing twigs, leaves, branches, and bark. But beware of the quirky little trick botanists like to play-after enticing companions with sample after sample of mints, sages, and tarweeds, slipping in a ringer like skunkweed without warning. Would a skunkweed by any other name smell as … awful?