This year’s special flower show

Monument plants are blooming!

by Dr. David Inouye

At intervals of two to eight years we’re treated to a special floral display in this area, and this is one of those years, the first since 2019. That’s how long it is between the mass flowering events of Frasera speciosa, the monument plant, or green gentian. Most of the several species of gentians found here have purple flowers and don’t bloom until August. Frasera has green and white flowers, and is already in bloom. Look for the 4-6-foot-tall stalks with lots of white/green flowers on them, now found in all the valleys around the area.

Another unusual aspect of the biology of these plants is that they only flower once, and then die. On average in the East River Valley, near Crested Bute, it takes about 30-40 years for these plants to store up the energy they need to put up a flower stalk that can be as tall as 9 feet, and averages about 600 flowers; I know this because I followed plants I started from seed back in 1982. It took 21 years before the first one flowered. At a site near Cumberland Pass, at 12,300 feet in the alpine tundra, I think plants may be as old as 80-100 years before flowering, although the stalks there are only 1-2 feet high. We’re following a few thousand individually tagged plants there in an annual census started in 1973.

Given that they only have one opportunity to reproduce, it’s not surprising that the plants put a lot of energy into the effort, making themselves visually conspicuous and highly attractive to pollinators. All the resources the plants have stored in their root for decades are devoted to producing the large stalk, hundreds of flowers and thousands of seeds. About 100 species of insects have been recorded visiting the flowers, and even hummingbirds will collect nectar from them. Probably the best pollinators are bumble bees, although moths also do some nocturnal pollination.

Why do they have this unusual pattern of infrequent flowering? One advantage is that if you flower when your neighbors do, you can all benefit from the cross-pollination that results as pollinators move pollen from one plant to another. Those genetic benefits of cross-pollinating can be significant, compared to pollination among flowers on a single plant, which is the only option if you flower in an off year.

The mass flowering may also help to minimize the loss of flowers and seeds to herbivores. Deer will sometimes eat all the flowers and fruits they can reach on a stalk, and there are also some insect seed predators. A potential disadvantage of mass flowering is when you all flower in a bad year for pollinators, like this year. There are few bumble bees this summer, probably because queens were frozen while overwintering underground last winter, because of the late and low snowpack.

So how can you time your flowering so that you’re synchronized with your neighbors? We know that mass flowering events can occur over large areas, even multiple states where the plants occur. My guess was an environmental cue, and it took me about 30 years to figure it out. If we have a wet June – July, then four years later a lot of Frasera plants bloom. The plants have to reach a certain size threshold before they become susceptible to that environmental cue, so some of the variation in height that you can see comes from variation in the number of leaves they have before they flower, which can vary from about 16 to 90.

This insight into their flowering comes from a project I started in 1979, counting all the flowering stalks I can see while driving up the Gothic Road from Mt. Crested Butte to Emerald Lake. Those counts have ranged from two (a few different years) to 31,177, a record set in 2019. I don’t yet know what this year’s total will be, but in a plot in the

Brush Creek drainage there are more flowering stalks this year than any year since 1979.

Drought may affect the flowering and abundance of these unusual plants in at least two ways.

First, in dry years a lot of seedlings die, as they can’t put a root down as fast as the soil is drying out during the summer.

Second, flowering events will become less common as summer precipitation declines. I’ve been seeing a decline in the number of non-flowering plants in some of the plots where I’ve been following them for decades, although I’m not sure yet why. It would be sad to see them becoming less common in the future, here in the wildflower capital of Colorado.

The only way to figure out the interesting story behind some of our local plants (and animals) is to return year after year to see what they’re doing.

We’re fortunate to have the Rocky Mountain Biological Laboratory in Gunnison County, which is internationally renowned for the cutting-edge and long-term science that’s done there. The group of scientists I work with at RMBL are also fortunate to have some financial support from the National Science Foundation (thank you taxpayers!), helping us to bring new students and teachers to Gothic each summer for training in field biology. Stop by the visitor center if you’d like to learn more about our work, and come hear some of our public seminars about RMBL research.

David Inouye has worked at RMBL since 1971, and spends winters in the North Fork Valley near Paonia.