Plants of the Western Slope September 16, 2015

By Evelyn Horn


Plants of the Western Slope September 16, 2015 | Evelyn Horn,

Photo by Evelyn Horn Gum weed plant seen on North Road

Gum Weed

What a summer this has been! Fairly cool with lots of rain showers and fast growing weeds. There is still lots to see scattered along North Road and here is one of my favorites!

It's Gum Weed that I knew in Nevada, Utah and California. Allen finds a place to pull off the road. And I'm out of the car to study this sub-shrub.

It's about a foot tall and covered with bright yellow flowers. I pinch a leaf and a thick, white substance oozes out -- gum weed. Since it occurs in a variety of soil types, this plant is expanding its range north to Minnesota and British Columbia, south to Texas and west to California. Gum weed usually occurs in dry areas up to 8,000 feet elevation. The alternate leaves are oblong, sessile (no leafstalk), sticky and up to three inches long. The edges are toothed, often almost spiny to the touch.

In the sunflower family there are often two types of flowers in each blossom. The outer "petals" are called ray flowers while the center of tiny tubular flowers are called disk flowers. In gum weed, each inch-wide flower head has 20-40 ray flowers and a dense center of disk flowers. The individual flowers are held together by small, leaf-like structures call bracts or phyllaries. In gum weed, the bracts or phyllaries are very noticeable with more than four layers or rows and all the tips protruding outward and downward.

The Latin term describing this par-ticular arrangement is "squarrosus," hence our plant's botanical name is Grindelia squarrosa in honor of D. H. Grindel, the 18th century Russian botanist.

Other common names are curly-cup, gum plant, rosinweed and tarweed. There are over 50 species in the genus or group Grindelia, found in North and South America, with 10 species in the Rockies. I've found no mention of the plant as an edible, but it is of significant medicinal value in the treatment of throat, lung, stomach and bladder ailments, and skin irritation, including poison ivy.

Enjoy our clear blue skies and lovely autumn wildflowers.