Mountain Tarweed

Madia glomerata

Species distinguishing characteristics: 

  • Whole plant is strongly aromatic and reminiscent of tar
  • Long, sticky glandular hairs cover foliage and flower bracts
  • Stems solitary and unbranched
  • Clusters of flower heads usually with 1 to 3 yellow ray flowers
  • Each ray flower encloses a sticky, hairy bract

Family Characteristics: 

  • Multiple layers of bracts beneath the flowers
  • Flower heads composed of many smaller (often tiny) flowers, each of which produces an individual seed
  • Flowers may contain disk florets, such as those in the yellow center of a daisy, and/or petal-like ray florets
  • Undivided leaves
  • Includes the food plants lettuce, artichoke, and endive

Growth habitat: 

Erect annual, 10-95 cm tall, from a taproot.

Leaves and stems: 

Long, sticky glandular hairs that smell like tar cover foliage.  Stems are solitary and unbranched or have a few ascending branches and no leaves at the base.  Alternate stem leaves, 2-9 cm long, are narrow and linear.

Flowers: 

One to several small clusters of flower heads in upper leaves.  Each flower head has 0 to 3 (or up to 5) greenish-yellow petal-like ray flowers, 2-7 mm long, and 1 to 10 reddish yellow disk flowers.  A sticky, hairy pointed bract, up to 9 mm long, encloses each ray flower and forms a spindle-shaped single series of bracts, 5-11 mm wide, below each flower head.

Roots: 

Taproot.

Seeds: 

Black, flat, hard-coated seeds (achenes), 4-6 mm long, are covered in sticky hairs.  Seeds lack a tuft of hair (pappus) at the tip.

Habitat preferences: 

Grasslands, open woods, roadsides, and disturbed areas at low to mid-elevations.

Interesting facts: 

The sticky “tar” acts as a defense mechanism by deterring grazing animals.  However, honeybees use the flower pollen and ground squirrels use the seeds as a source of protein rich food.  The tar-like scent varies from plant to plant and has been compared to balsamic vinegar and pheromones.  Some people find the smell objectionable, while others enjoy it.  The Blackfoot people burned dried plants as incense.  Made into an herbal bath, the leaves and stems were used to treat venereal disease.

Biological Classification: