I posted last year about bladderwort in a pond (Utricularia is the formal name – more on that in a bit). For several years, it bloomed like a carpet. In some years, it was a lush carpet, and in others, thinner, but still extensive.
This year, there were essentially no Utricularia in the pond. Probably not zero, but nothing even hinting at a carpet of flowers.
There are lots of animals that irrupt and become conspicuously abundant. Lymantria dispar, the soon-to-be-renamed gypsy moth, is one infamous example, and there are many others. Periodical cicadas are NOT an example – they just have a weird life cycle. But the annual cicadas in some places are an example. In sixteen years of field work among pinyon pines near Sunset Crater, Arizona, there were always a few cicadas around, except in one year when they were practically dripping from the trees. The next year, they were just around, not abundant. Why? I have no idea. And maybe nothing is more irruptive, and more mysteriously so, than the freshwater “jellyfish” Craspedacusta sowerbii. I saw it in a campus pond in 1979, and never again. It was spotted in 2020 in Walden Pond. It appears in a pond and then vanishes, only to appear in another pond years later. How does it do that? Who knows?
But are there irruptive plants? Algae blooms, sure. But vascular plants? The mast years of tree seeds or blooming years of desert annuals don’t qualify because they are always there, just not always reproducing or germinating. Perhaps gentians qualify, here this year, elsewhere the next, though they rarely get superabundant. I would not be surprised if there are truly irruptive plants, but I just don’t happen to know of any.
Except bladderwort. Utricularia just went through a boom and bust on my neighborhood pond, and I think that’s pretty amazing.
Now I have to admit that there’s a problem: I don’t know the species of bladderwort. It looks like the pictures of U. radiata (floating bladderwort) or U. inflata (swollen bladderwort), and I don’t have any specimens to check and confirm the identification. Both species have floating leaves and light yellow flowers. Both live in shallow ponds. But swollen bladderwort is said to be invasive, and invasive species often have the ability to grow quickly. That would be consistent with the sudden appearance of a carpet of plants on the pond. But their rapid demise was a surprise. So whatever species it is (I’m leaning toward U. inflata), I think it qualifies as irruptive.
So maybe – just maybe – the concern over an invasive bladderwort might be tempered a bit if their populations are likely to collapse after a few years. It would be helpful if we had more data, more observation of bladderwort populations over several years. If they consistently disappear, then maybe all we have to do is wait. That’s my hopeful hypothesis, and I look forward to learning whether I’m right.