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COBB TRAIL WILDFLOWER WALK
mid April to mid May

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Description: This is one of the more challenging of the recommended wildflower walks, approximately 4 miles roundtrip (out and back) with 1000 foot elevation gain, on a (mostly) well-graded road. The goal is an uncommon “windswept ridge” habitat, with other interesting plants en route. 

NOTE: Please enjoy the wildflowers and leave them for others to enjoy.  Because our unique local flora is already under pressure from invasive weeds and habitat loss, harvesting of native plants is not encouraged on this website, especially along popular trails.

The walk begins at Highland Valley trailhead at the end of West Highland Valley Road off of east Warm Springs Road, in the East Valley development of Harris Ranch.  Follow the West Highland Valley trail about 1/3 mile, taking note of shrubs and flowers along the roadside bank.  Turn left on Cobb Trail, which immediately drops down to a small shrub-lined creek.  There is a good diversity of wildflowers on the relatively intact north-facing slope above the creek, including the lovely longspur (“polychrome”) lupine (Lupinus arbutus). 

About another 1/3 mile from the creek crossing, the trail traverses a ridge where the recently described Andrus’s biscuitroot (Lomatium andrusianum) grows.  This plant had previously been shoe-horned into nine-leaved biscuitroot (Lomatium triternatum), but recent molecular work by botanists at Boise State University and The College of Idaho showed that it was a distinct species.  In an attempt to generate funds to continue their research on Lomatium, the “naming rights” for the new species were auctioned off, with the winning bid choosing to honor former Idaho governor Cecil D. Andrus.

From the ridgeline, the trail traverses a west-facing slope where sharp eyes can sometimes spot the early-blooming Beckwith’s violet or sagebrush pansy (Viola beckwithii) and goosefoot violet (Viola purpurea ssp. venosa).  An old homestead is encountered at about 1.5 miles from the trailhead, recognized by the naturalized grove of black locust (Robinia pseudoacacia, not in bloom until mid summer) and associated weeds growing around a spring. 

A couple of hundred feet north of the homestead area, mostly on the south side of the trail, look for rigidly branched white-flowered shrubs whose presence in the Boise foothills is a bit of a head-scratcher.  This the Mojave ceanothus (Ceanothus vestitus), growing a long way from its Mojave Desert home.  This is presumably one of the survivors of experimental plantings by the Rocky Mountain Research Station in the 1960’s and 1970’s when the goal was to improve deer winter range, with a focus on growth rates, protein content, winter leafiness, and palatability, but little regard for native range except the western US in general.  There are also a couple of Apache plume (Fallugia paradoxa) from the same origin, but not doing as well as the ceanothus.  Bitterbrush (Purshia tridentata) planted in rows on the hillside above are further evidence of experimental plantings.

 

The final half mile ascent (ca 400 feet elevation gain) is relatively steep and rocky; hiking poles recommended if so inclined.  The reward is both fine views and an entirely new suite of plants on the wind-swept knoll.  Although the summit is tempting, please stay on the path, since this seemingly barren site is actually a delicate habitat.  If your timing is right, you’ll be able to enjoy both tufted carpet phlox (Phlox caespitosa) and scabland fleabane (Erigeron bloomeri). 

From this point, you can either retrace your steps, or else continue on a 5.7 mile loop via Lucky Peak and West Highland Valley trails (described in reverse in Scott Marchant’s The Hiker’s Guide: Greater Boise).

PLANT LIST [updating needed]

NOTE: Please enjoy the wildflowers and leave them for others to enjoy.  Because our unique local flora is already under pressure from invasive weeds and habitat loss, harvesting of native plants is not encouraged on this website, especially along popular trails.

Download plant list pdf

Plants listed in approximate order of occurrence within category; some might not yet be in bloom, or present during a particular year.  * indicates native

WILDFLOWERS POTENTIALLY IN BLOOM

SHRUBS AND TREES (mostly not in bloom)

PRIMARY BUNCHGRASSES (not all in bloom, but evident)

SIGNIFICANT NOXIOUS WEEDS (mostly not yet in bloom, but evident)