Outdoors Blog

Discover the Boise Foothills: Hillside to Hollow’s rare plants

Hillside to Hollow offers one of the better “City of Trees” views in town.
Hillside to Hollow offers one of the better “City of Trees” views in town. ccripe@idahostatesman.com

This is the latest in our series of blog posts exploring different trails in the Boise Foothills. On many of those trips, we’ll be joined by an expert who can provide some perspective on the land that has become one of Boise’s most popular and valuable assets.

This week: Hillside to Hollow.

Previously: Introduction

If you want to see a fired-up botanist, hike through the Hillside to Hollow Reserve in the Boise Foothills with Ann DeBolt to check out one of the rare sand-verbena plants.

It’s growing right on the edge of a steep, sandy path that isn’t an official trail but clearly gets much use from people and dogs. You can tell from the footprints just inches from the plant.

The sand-verbena “was widespread in the sandy soil of the Boise Foothills” according to records, DeBolt said. Now she’s growing it at the Idaho Botanical Garden to try to replace some of what impacts from people, fire and non-native plants have wiped out.

The plant also can be found at Camel’s Back, Stack Rock and along Bogus Basin Road. The species in the Boise Foothills recently was identified as a new variety found only in sand hills and lake bed sediments on the north side of the western Snake River Plains in Southwest Idaho, according to a scientific paper written by Barbara Ertter of Boise and Sonia Nosratinia.

Fewer than 100 plants were located in 2015, they wrote in their paper on the plant, and one of the larger populations was on a site that has been purchased for development.

“It is not often that a new plant is described within walking distance of an author’s house, especially when that house is in one of the original neighborhoods of a capital city in the USA,” the paper says. “The unfortunate consequence is that (this variety) is ... in (urgent) need of conservation attention.”

DeBolt works at the Botanical Garden. She went to school at Montana and decided to study plants in part because many of her classmates were studying wildlife. She admits botany can be “discouraging” because of the challenges facing plants.

“We’ve lost a lot to development and also to the dang weeds,” DeBolt said.

But she also found some reason for optimism as we searched out the last of three rare plants we observed at Hillside to Hollow: Aase’s onion. That’s the plant that led to an on-leash policy for dogs at Polecat Gulch.

“It’s a pretty nice population here, which is great,” DeBolt (pictured below) said.

Botanist Ann DeBolt of the Idaho Botanical Garden. Chadd Cripe ccripe@idahostatesman.com

Hillside to Hollow, which covers 316 acres from just east of Hillside Junior High to just west of Bogus Basin Road, is a recent addition to the Ridge to Rivers system — and it highlights the balancing act between recreation and conservation in the Foothills. The land was purchased by the city of Boise (258 acres in 2013) and Land Trust of the Treasure Valley (58 acres in 2011) from dozens of separate landowners. An informal trail system has been on the property for years, used by neighborhood residents. A survey last year indicated that 76 percent of users bring a dog — by far the highest percentage in the Ridge to Rivers system.

The trail system remains in transition between the original trails and implementation of the 2014 Hillside to Hollow Reserve master plan. This year, the city hopes to build Full Sail Trail, re-align and improve Robert Smylie Trail, re-align the connection between the Harrison Hollow and Who Now Loop trails and re-vegetate some of the trails that will be abandoned. Re-vegetation efforts have begun and can be seen in at least a couple spots on the property.

Our hike started on the Harrison Ridge Trail, which overlooks Simplot Hill and Bogus Basin. We dropped down to the Harrison Hollow Trail, an all-weather surface that runs through the hollow and climbs to the rear of the property, to views of Quail Hollow Golf Course. We made a short foray onto the Buena Vista Trail, which has terrific views of the city and a nice supply of Aase’s onion on the hillside. Then we descended on Who Now Loop and Hippie Shake.

We covered 3 miles and 400 feet of climbing — and left more than half of the property unexplored.

DeBolt highlighted three plants:


▪ Mulford’s milkvetch (above), which is in the pea/bean family. It’s found in five counties across Idaho and Oregon (Malheur) and nowhere else in the world.

“Most people don’t know it exists out here,” DeBolt said. “It’s not very competitive. It has a tough time fighting. It’s very wispy and delicate.”

rare plant w footsteps

▪ Sand-verbena (above), the plant hanging out in a precarious location at Hillside to Hollow.

“That’s extremely vulnerable,” DeBolt said, looking at the footsteps in the sand.

There is only one other sand-verbena plant on the Hillside to Hollow property.

“It has a very beautiful, creamy white flower and it smells really good,” DeBolt said. “... This is fantastic for pollinators. It has a lot of ornamental value.”


▪ Aase’s onion (above), which grows in coarse sand. It blooms by mid-March with a deep purple-pink color. Most of the blooms have faded by now. It’s found in four Idaho counties and nowhere else, DeBolt said.

We found that “nice population” on the hillside above the Buena Vista Trail.

“It’s tiny and very low-growing,” DeBolt said.

Getting there: The primary trailhead for Hillside to Hollow is behind Healthwise off of Harrison Hollow Lane. There are five Healthwise parking spots available for trail users. Otherwise, you need to park on the street. Neighborhoods also have trail access to the property. The master plan calls for an eventual trailhead at Hillside Park off of 36th Street.

Coming next week: The Corrals Trail — and those pesky dog issues in the Foothills.

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