Driving down our roads, over a dozen rambunctious plants – “weeds”– catch the eye in early July.

With a bit of practice, even from a distance, you can identify the big patches of plants: windshield botany.

Different terms help describe their origins.  Many “weeds” are introduced to this area from afar–these we call “non-native” species.  Some non-natives are beautiful and benign—spreading slightly beyond our human landscapes—“naturalized”; other non-natives may be beautiful (or not) but are terrors—they spread in large numbers from roadsides into neighboring natural and agricultural areas altering their quality–these we call “invasive exotics”.

“Noxious weeds” are those listed by various agencies for control.  A few roadside plants are wonderfully resilient “natives”—locals that know how to get along in particularly tough, transient circumstances.  “Weed” is a loose term used by gardeners for plants out of place and by the public for those untidy, rampant interlopers—e.g. plants we don’t want around.  Wherever they are from, these common roadside species are interesting plants to investigate.

All the plants described here adapt well to disturbance.  Human disturbances are created during road, bikeway, and ditch construction and maintenance; utilities installation; and overgrazing.

Natural disturbances include landslides and flood-scoured shorelines.  Most “weedy” plants grow and propagate profusely in full sun, extreme wind, heat, and poor soils.

Many newcomers spread from nearby gardens, vehicle wheels, bird or cow poop, and muddy shoes or paws.  They are often annuals or biennials: plants that grow, set seed, and die within in a year or two.  They typically disperse 1000s of seeds per plant—their genetic survival strategy.  Perennial weeds have extensive root systems that enable them to form dense colonies, out-competing other species for resources. Invasive exotics and noxious weeds affect the productivity of our agricultural fields and the natural diversity of our native habitats.

Note: The plants with a (*) are targets for control by the Teton County Weed and Pest District and Grand Teton National Park Service.   For more information, please to go to: http://www.tcweed.org

Yarrow – Achillea millefolium – Yarrow grows in temperate zones around the northern hemisphere—circumboreal.  It has medicinal qualities historically used by Achilles during the Trojan War (hence the latin name: Achillea) and by our Native Americans, and still today by herbalists.  The flat “cymes” of white flowers and soft, fern-like leaves have made this plant distinctive for millennia.

Blue Flax – Linum lewisii –These sky blue flowers open wide to the morning sun, thereby attracting bee and fly pollinators. Their many skinny, 1” leaves are arranged alternately on slender, 2-3’ delicately branched stems that bend with the breeze. It is related to the European Flax (L. usitatissimum), still used for making linen. This is a beautiful native found along roadsides and into sagebrush and montane communities.

Dalmatian Toadflax* – Linaria dalmatica – Related to garden snapdragons, this persistent invasive exotic has yellow flowers with long spurs born arranged at the tops of straight, 2-2.5’ stems.  Each plant can produce 500,000 seeds that can live in soils for ten years!

Oxeye Daisy* – Chrysanthemum leucanthemum/C. vulgare – Introduced as a garden ornamental for its showy flowers, the wavy-lobed, 2-3” long leaves are unpalatable and irritable to both wildlife and livestock. Oxeye Daisy invades readily into pastures and up mountain slopes by seed and root.  While it is tempting to keep a few plants for flower arrangements, their side effects are not worth it!

Dame’s Rocket* – Hesperus matrionalis – This attractive plant from Eurasia is a garden escape often found in our subdivisions.  Note the 4 purple (sometime white) petals that flare at the ends.  This is a large-flowered member of the Mustard Family and releases 1000s of seeds in a year.  The fruits ripen into elongated siliques.  These short-lived plants extend their roots quickly into new habitats, affecting wildlife values of aspen groves and the like.

Foxtail Barley – Hordeum jubatum – Not quite waving amber waves of grain, this shining blond-to-rose-colored grass festoons road edges.  While the 8-12” plants look soft and silky, their grains are encased in stiff spears (awns and glumes) that deter grazing animals.  The barbed seeds easily attach to passing tires, shoes, and fur. This is a tenacious native.

Cheat Grass, Downy Brome* – Bromus tectorum  – The scourge of grasslands throughout the West, this quickly growing annual is unpalatable to livestock or wildlife due to its sharp, hurtful awns.  It crowds out nutritious native grasses and changes the ecology of shrublands and grasslands by altering the fire regime: the fast-curing plants provide tinder for fires from spring to fall.  Look for the purplish to brown patches spreading from roads up the slopes of our buttes.

Yellow Sweet Clover – Melilotus officinalis – A member of the pea family hailing from Europe, this 2-5’ plant. can fix its own nitrogen, enabling it to grow on the poorest of soils. The tiny, yellow, pea-like flowers have a sweet fragrance from the presence of coumarin.  In moist hay, coumarin can be converted by fungi into a poisonous anticoagulant, called dicoumarol—toxic to cattle.  Natural area managers target Yellow Sweet Clover for its aesthetic and ecological alteration of our beautiful grassland and shrub habitats. In Jackson Hole it is well established along roadsides and buttes.

Bladder Campion – Silene latifolia – Introduced from Europe, this naturalized species is a delight to investigate.  The fragrant white flowers bloom at night into the next morning, attracting moth, bee, and fly pollinators.  Plants proffer either male or female flowers.  The 5 sepals (outer whorl) form a sac and the five white petals flare out above it.  Male flowers have only anthers which barely reach beyond the petal tube.  Females have 5 extended, curling stigmas ready to grasp the pollen relayed by a visiting pollinator. Once fertilized, over 100 seeds may form inside a dried capsule, to be shaken out by the wind, like grains of salt from a salt cellar. Females extend curled stigmas and have a more pregnant looking calyx than the male flowers.

Tumble Mustard – Sisymbrium altissima – This 3-4’ tall, airy plant has ½”, 4-petaled yellow flowers and 3-4” very narrow fruits (siliques).  The stem leaves are pinnately divided into narrow segments while the basal leaves are much broader and larger overall.  This is a very invasive plant, which dries quickly, breaks from its roots, and tumbles its seeds across open spaces.

Salsify or Goatsbeard– Tragopogon spp.  The giant dandelion-like flowers are seen here and there along roadsides and fields. Right now their flower heads are ripening into fluffy but often dingy, 3- 4” spheres. Each elongated seed has its own elaborate parachute.  Take a close look!  We host 3 species naturalized from Europe.

Thistles* – Canadian thistle (Cirsium vulgare) and Nodding or Musk Thistle (Carduus nutans) are  just a few thistles from Europe targeted for eradication.   These spiny plants overwhelm many pastures and grasslands.   

However, there are also native thistles, such as – Cirsium scariosum, which are highly beneficial to insects and larger wildlife. In a later blog, we will help you identify the native thistles from the exotic invasives.

 

So while you are driving, biking, or walking stop and take notice.  Dissect the flowers. Examine the fruits and seeds.  Smell and feel the leaves.  Think about why these plants are so successful.

And as always, we appreciate your comments, corrections, and questions.

Frances Clark, Wilson, WY

P.S. This essay is about native and non-native plant species.  Absolutely no inference should be made to our many visitors or workers from around the country and world, whom I welcome here in Jackson Hole.