Another of the many yellow-flowered members of the aster family (Asteraceae) that are especially prevalent in the fall is the pricklyleaf dogweed. One can hardly blame those frustrated botanists who, when they come across a plant of this ilk, have been known to mark it down as another DYC (damn yellow composite). Yet careful observation of key characteristics can usually lead to a more precise identification, and in the case of Thymophylla acerosa it pays to take a close look at the slender pointed leaves and the phyllaries surrounding the base of the floral head which will reveal the presence of surface glands that give the plant a strong unpleasant odor. Plants in the genus Thymophylla are generally known as dogweeds and there are five native dogweed species in New Mexico. From the Greek words thymos, referring to the plant thyme, and phyllon, meaning leaf, this species name suggests plants with leaves similar to thyme, especially with regard to the presence of a strong scent. The specific epithet is derived from the Latin acer, meaning sharp, and osa suggesting in abundance or of full development. So acerosa refers to the presence of stiff, needle-like leaves. This characteristic is also reflected in some of the other common names for pricklyleaf dogweed; spiny dogweed, shrubby dogweed, and dog fir.
Widely distributed throughout New Mexico on dry, rocky calcareous slopes, pricklyleaf dogweed is a rather small perennial reaching perhaps eight inches tall and rarely one foot across. But it is technically a shrub because its lower branches are indeed woody. The leaves are slender and sharply pointed, quite reminiscent of the needles on a fir tree. Often found growing in clusters along the stem, the leaves have small translucent oil glands on their surface. At the end of the growing season the green leaves fall off leaving a barren tangle of extensively-branched woody twigs.
Pricklyleaf dogweed blooms through much of the season (June – November), but is especially noticeably in the fall. The bright yellow floral heads are quite striking against the deep green leaves and typically measure just less than an inch across. Each head has seven or eight ray flowers surrounding 18-25 smaller disk flowers. The base of the floral head is columnar, sheathed by phyllaries that have both short fine hairs and orange/brown oil glands on their surface. Those glands also contribute to the distinct fetid odor of pricklyleaf dogweed.
As one might expect, this yellow-flowered, strong-smelling plant did not escape the notice of Native Americans. The Isletas are reported to have made a decoction from the leaves for use as a body bath to treat fevers. And the Western Keres would gather pricklyleaf dogweed leaves and mix them with tobacco prior to smoking. Indeed this small, sometimes inconspicuous shrub is capable of having a major impact on our senses of sight and smell, especially in the late fall when its vibrant yellow bouquets light up a landscape that might otherwise be considered somewhat drab.
© 2011 Jerry Melaragno