Rare Plant Numbers Up

by Mike Kelly, Conservation Chair

On June 2nd of this year the Friends of Peñasquitos Canyon Preserve joined with the City of San Diego Multiple Species Conservation Program to survey one of our most endangered plants, the beautiful, dainty Thread-leaved Brodiaea (Brodiaea filifolia). It’s located in Black Mountain Open Space Park. According to City Senior Biologist Sara Allen we found and GPSed 152 “clumps” and counted 1,868 scapes! Scapes are the bloom stalks sporting a bloom or bud.

Allen led the City MSCP team which included two hard working interns. Black Mtn. Ranger J.J. Paetow, who has a sharp eye for finding this plant, joined us and was quite involved in the surveys. Justin Daniels, president of the local chapter of the California Native Plant Society, who was a participant in surveys in past years, came and helped us get started before he had to leave for another CNPS commitment. Our volunteers included myself, Cindy Burrascano, Jeanie Anderson, Del Brooks, and our president, Beth Mather.

City Ranger JJ Paetow and Friends President Beth Mather counting Brodiaea flowers. Red flags outline a clump, the orange “whiskers” and a numbered blue tag give us a way to track this clump over the years.

Photo by Mike Kelly.

This location of B. filifolia is the southernmost known population, discovered in 2010 by my crew and I before I retired my Wildlife Habitat Restoration business. Our survey day was perfect, overcast and cool. At one point I looked up to see the peak of Black Mountain shrouded in clouds and mist, beautiful.

This species is a perennial herb (bulb or corm). It’s an endemic plant, found only in Southern California. Its California Rare Plant Rank is 1B.1 (rare, threatened, or endangered in CA and elsewhere). Its State of California status is Endangered while its Federal status is Threatened. This Brodiaea is found only in San Diego, Riverside, Orange, and Los Angeles Counties. With our higher-than-average rainfall it’s a great year for Brodiaea, whether B. orcuttii found in our Lopez Ridge vernal pools or the B. filifolia found on Black Mountain. Wetter years like this tend to bring up more flowers from seed or bulbs than drier years.

While Sara and an intern ran a more general survey of the associated vegetation the rest of us split up into teams. Adam and I went to already identified clumps of the Brodiaea and placed small metal posts with a brightly colored “whisker” (flagging surveyors use these flaggings) and a numbered metal tag on it into the ground next to it. Adam then used a smart phone app to enter gps data and the metal tag number into a database and interactive map. We then counted the number of scapes, stalks with blooms or buds on them and entered that data. This will allow super accurate tracking of this population in future years.

Concurrently, the other volunteers and our Ranger spread out to find other clumps and place tags on them. They also looked for and found, as Adam and I had, “new” plants or clumps. By about noon we had finished the big site and moved perhaps a football field length away to an upper terrace where Cindy had found another subpopulation and repeated our surveys. We and the City will compare this flower/scape count with a count of Brodiaea leaves we took earlier this year. As anybody who has gardened with bulbs has experienced, many new bulbs don’t produce blooms in their first year of growth. They need one or several years of growth to have a big enough bulb with enough stored energy to “pay” for the high energy cost of blooming. Some experts in this plant genus say that as few as 1 in 8 or 1 in 10 plants will bloom in a given year, hence our counting twice this year. We want to get some data points on this cyclical lifestyle. By the way, by the time the bloom bolts the leaves have died back on the plant. The slim profile of the leaves of this plant, hence the common name Threaded leaf, make it hard to find in a field of other, bigger plants.

Challenges to the continued existence of this plant include development and invasive plants, and perhaps climate change (yet to be determined). One of the biggest populations in San Diego wasn’t even found until a development had been approved for the site! Somehow, an environmental company hired to do such surveys during the development process, didn’t find this population estimated in the hundreds of thousands. In fact, it was our discovery of the southernmost population that led the City to require additional plant surveys of this proposed development underway on the other side of Black Mountain. Luckily, the biologist hired to redo the surveys was one of our local experts in this Brodiaea. As a result, the developer was ordered to redesign the project to avoid most of the Brodiaea but to transplant some of it as well. A big challenge for our southernmost population is invasive plants. We found the Brodiaea because I had a contract from the City to work on controlling/eliminating invasive weeds, especially the perennial ones in Black Mountain Park. Certain invasives are highly threatening to plants such as our Brodiaeas. One in particular, Artichoke thistle (Cynara cardunculus) was abundant in the fields with this endangered plant. Besides competing for sun and water the thistle competes for physical space underground by growing a large tuber that occupies more and more space, often at the expense of other species. Sweet fennel (Foeniculum vulgare) was another perennial weed that can expand to very dense stands excluding other plants. Black mustard (Brassica nigra) and Bristly oxtongue (Picris echioides) are two annual weeds that can be very dense and crowd out our Thread-leaved brodiaea. The Friends have been killing these various weeds for years now, with some success. The fennel and artichoke are down to an occasional seedling. The battle is now on to eliminate the mustard and oxtongue. But the grasses are to be an even bigger challenge. Some experts think the Brodiaea can compete well with these invasive grasses such as the two oat species present. We don’t agree and will begin to knock the grasses back.

One of the exciting aspects of this grassland is the presence of a nice variety of native species such as Lupine, Goldenstars, Death camas, a ton of Gum plant, purple needle grass (the State grass of California), Blue dicks, blue-eyed grass, golden bush, California sunflower, and others.

You can help us with these challenges; we’ll be doing both chemical and mechanical (hand pulling) in the future.

Sources used: Calflora

Closeup of Brodiaea filifolia

Photo by by Janet Nelson, former Board member of the Friends of Los Peñasquitos Canyon Preserve.

B. Filifolia challenged by invasive grasses (wild oats here)

Photo by Mike Kelly