Hiking Irish Hills Natural Reserve
Tucked in the rolling landscape of the Irish Hills Natural Reserve in San Luis Obispo is a rare plant species: the Irish Hills spineflower.
The little plant hid in plain sight for decades, until a sharp-eyed botanist came along.
The path to discovery began in early 2017, when the city of San Luis Obispo acquired the 154-acre Waddell Ranch, a triangular-shaped stretch of land on the southern boundary of the Irish Hills that contains the source of Froom Creek, artesian springs, rare plants and wildlife habitat, according to a 2017 Tribune article about the purchase.
Two of the known plant species on the property were Brewer’s spineflower and Palmer’s spineflower, according to Robert Hill, the city’s natural resources manager.
The city employed San Luis Obispo’s Terra Verde Environmental Consulting to perform a biological assessment of the new property.
One June day in 2017, Kristen Nelson, a Cal Poly graduate and the lead botanist conducting the assessment, noticed that the spineflower she was examining didn’t look like another spineflower close by.
“The Irish Hills spineflower frequently coexists near Brewer’s spineflower and they do look somewhat similar,” Hill said in a phone interview with The Tribune on Tuesday. “But it was not until Kristen looked really, really closely that she found a little bit of difference.”
The spiky green plant is tiny, measuring just a few centimeters to a few inches in height.
Nelson met with Hill and David Keil, a Cal Poly professor emeritus, as well as Cal Poly professors Matt Ritter and Jenn Yost, to verify that she discovered a new species.
Since the discovery was made at the end of flowering season, Hill said he asked Nelson to go out again in the spring and early summer of 2018 to reassess the site where she first discovered the new spineflower.
Following that, a team of botanists led by Nelson discovered that the plant was growing all over the Irish Hills Reserve.
The team submitted the discovery to Madroño, the California Botanical Society’s peer-reviewed scientific journal, and plans to recommend the plant for inclusion on lists of rare plants for the state of California and the California Native Plant Society, Hill said.
To date, the Irish Hills is the only known location where Irish Hills spineflower grows, the city said in a news release Tuesday.
“It’s endemic, or native, to land that has serpentine soil and rock — a unique chemical composition that we see at other properties like Laguna Lake and the South Hills,” Hill said, noting that scientists have not found Irish Hills spineflower at those locations. “It’s a unique microclimate in the Irish Hills that’s supporting this plant.”
Hill said scientists plan to keep studying the plant, so they can answer a “treasure trove of research questions,” including where the plant fits into the Irish Hills’ environment and how it propagates.
“This is why we do conservation work: to protect these species where sometimes we don’t know they exist, but now they’ll be there for all future generations,” Hill said. “There are numerous rare plants in Irish Hills. It’s a botanist’s delight.”