The year 2024 marks the 50th anniversary of the CNPS Rare Plant Inventory (RPI), an authoritative rare plant database and ranking system that has helped protect approximately 2,450 rare plant taxa in California since 1974. To celebrate, each Rare Plant of the Month in 2024 is a plant that experts added to the RPI 50 years ago.
By Ellen Dean
This month, we are celebrating a plant in the rose family, Tahquitz ivesia (Ivesia callida), also known by the cute name Tahquitz mousetail. Tahquitz ivesia is known from only two locations in the San Jacinto Mountains of Riverside County, including Tahquitz Peak. This lovely perennial herb with white flowers grows in the cracks of nearly vertical cliffs on igneous substrates. Igneous rock is a type of rock that forms when lava or magma cools. Since Taquitz ivesia grows vertically, it sometimes takes the form of a hanging plant. Because of its preferred habitat, people have a difficult time finding and photographing it. Potential threats to its existence come from fire suppression actions, trail building, and rock climbing.
Tahquitz ivesia was presumed extinct (California Rare Plant Rank 1A) when the first version of the California Rare Plant Inventory was published in 1974. At that time, it had not been observed since the 1920s. It was rediscovered in 1980 at two sites in the San Jacinto Wilderness Area of the San Bernardino National Forest. In 1982, Tahquitz ivesia was listed as rare by the State of California, and its Rare Plant Rank is now 1B (plants rare, threatened, or endangered in California and elsewhere). Tahquitz ivesia is now known from several thousand plants. The rediscovery of presumed extinct plants is always something to celebrate!
Ellen Dean is Associate Rare Plant Botanist at CNPS, helping complete rare plant profiles. In a previous life, she was an herbarium botanist, performing plant IDs, leading collecting field trips, training students in plant identification, curating the herbarium, and publishing taxonomic papers.
