Lake Tahoe Wildflowers: The Sinister Mustard Flower Rust

Copyright © 2015 Jared Manninen

I always stop to appreciate Sierra Nevada wildflowers while hiking. However, my love of specifically hunting for them comes and goes like the seasons. Some years I’m simply more active in my search for the small treasures. Other years, I’m more interested in logging miles.

But one of those active years of searching for wildflowers was in 2015. At the time, I was hiking a series of short trails near my home in South Lake Tahoe gathering trail data and reference photos for a future project (which essentially became this website).

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That spring was preceded by a low snow winter and a few drought years. So, even though there was still snow higher in the mountains, by March I was hiking on dry trails at 7,500 feet.

On March 6, 2015, I hiked to Tahoe Mountain and found my first wildflower of the season. Or so I thought. It seemed very odd that I would find something blooming so early because it was, after all, barely the first week of March. Drought or not, that’s exceptionally early for wildflowers to be blooming at Lake Tahoe.

But there it was growing out of the sandy and rocky soil near the top of Tahoe Mountain. The flower petals were lemon yellow in color and its stem was covered with dark green and purple leaves.

The curious thing about this “wildflower” was that, except for the change in color, the transition from the leaves on the stem to the petals on the flower was seamless. It looked like someone had just spray-painted the tops of this leafy plant yellow and called it a flower.

I took some photos and went home to research the plant. No luck. I posted pictures on social media in hopes that one of my friends more savvy in the identification of Sierra Nevada wildflowers could help me out, but still no luck.

Ten days later I was hiking along Angora Ridge, which is a close neighbor to Tahoe Mountain, and I found more of those mystery flowers. A lot more.

This time, however, the flowers didn’t appear to be in full bloom as they were still lime green in color. My assumption was that the whole plant started out as a uniform color of green and, as it matured, the contrast between stem (leaves) and flower (petals) would become more pronounced like the flower I found on Tahoe Mountain.

Copyright © 2015 Jared Manninen
Mustard Flower Rust (Puccinia Monoica) in “bloom” on Tahoe Mountain on March 6, 2015. © Jared Manninen

In spite of discovering this new evidence, neither I nor any of my friends could determine what it was that I had actually found. There were so many examples of the plant on Angora Ridge, yet I couldn’t find a single image of it in any reference book relevant to Sierra Nevada wildflowers.

Two months passed before curiosity finally got the best of me.

On May 3rd I returned to Tahoe Mountain to see what became of the flower in question. To my surprise, nothing remained of its existence. Three days after that I went back to Angora Ridge in search of evidence of that mystery flower mother lode.

This time, however, I found remnants of the unidentified flower. And I not only found remains of those mystery flowers, but I also found a new (to me) wildflower sprouting from one of the dying bunches.

It was confusing to look at due to the jumbled mess of bloom and decay. However, once I traced the stem from the head of the new flower down to its base it was clear that one sprouted from the other. I took some photos and renewed my investigation.

What I ultimately discovered was both intriguing and creepy. Of the two varieties of flowers, only the second of them (the one that was sprouting from the other) was an actual Sierra Nevada wildflower. It was a type of Rockcress and, not surprising, grows in dry rocky areas.

The flower at the root of this mystery was not actually a flower at all, but rather a parasitic rust fungus called Mustard Flower Rust (Puccinia monoica). That strain of rust fungus likes Arabis plants which is within the mustard family (Brassicacea), of which Rockcress is classified.

In early spring Mustard Flower Rust takes over a host plant, inhibiting it from procreating, and then manufactures yellow pseudo-flowers in place of the plant’s true flowers.

The fungus uses these fake flowers to attract bees and insects. But the pseudo-flowers don’t just look like real flowers to the naked eye. They’re also ultraviolet and they emit a scent.

Combined, all three features provide a compelling argument that attracts bees and insects. As a result, the bees and insects spread the rust fungus instead of pollinating the host flowers (in this case the rockcress).

At some point during my recollection of this experience (and subsequent note taking sessions for this blog), I sat in on an episode of the older television series Stargate SG-1. My roommate had been revisiting the series. And, the episode featured a courtroom trial where two factions argued for their respective comrades’ right to life.

The reason this episode caught my attention was because the two entities at the center of this case inhabited the same body. The parasitic entity called the Goa’uld (pronounced as it’s written) invades a host person.

The Goa’uld are a fictional race of worm-like creatures that fix themselves to a host’s brain and spinal cord and then take control of the host. They invade other beings because their worm-like bodies are bound to water. By taking over a host body they are able to travel beyond their natural habitat.

Interestingly, the host does not actually die for if it did the parasite would have to find a new host. In the case of the trial, the Goa’uld’s position was that the host was still actually alive and both were simply sharing the same body.

However, the opposition (good guys) argued that just because the host was alive didn’t mean that he was living. Essentially, the host no longer had free will and became a prisoner trapped in his own body.

Clearly, drawing a parallel between a parasitic rust fungus attacking Sierra Nevada wildflowers and a fictional race of alien parasites that take over other forms of life is a stretch. As an artist, however, I’m fascinated by art that imitates life and vice versa.

I also like to find connections between seemingly unrelated things or concepts. So, even though many people site passion as the big motivator behind leading a fulfilling life, I would argue that passion stems from curiosity.

And, that curiosity is the true source of fulfillment.

Curiosity returns us to a “beginner’s mind” and causes us to ask “why, what, when, where, and who?”

So get outside and do your thing, but be sure to stop every once in a while to appreciate what the world around you has to offer. You may just discover a mystery that leads you down a new path.

Rockcress sprouting from a bunch of Mustard Flower Rust (parasitic rust fungus). This was one of the only examples of the Sierra Nevada wildflower that survived the motherlode of rust fungus discovered two months prior.

In addition to performing online searches (including the amazing site iNaturalist), the books I typically use to identify Sierra Nevada wildflowers are:

I also like to reference small pocket guides such as these. Although they’re usually limited as to what they provide for identification, they’ll occasionally feature a small surprise or two. And, purchasing them often goes toward supporting nature and ecologically based organizations.

Tahoe Area Plants & Animals, Great Basin Outdoor School and Nevada Fish & Wildlife Education Project (ISBN: 9781583556504)