June 8, 2022
From a distance, it’s easy to dismiss the grassland. A green wash on the hills: so what? Sitting in the middle of it at this time of year, it’s much harder to ignore. You might need to get down on your belly to really appreciate it, though.
Today, that’s exactly what I’m doing. I’m perching on a rocky hilltop a thousand feet above the Helena valley, looking out over Silver Creek and the sagebrush beyond. Marisa Diaz-Waian has invited me here, to the Merlin Nature Preserve near Marysville, to get hands-on with grassland ecology.
Marisa is passionate about wildlife habitat. Here, with support from the NRCS Conservation Stewardship Program, she hopes to boost native plant diversity, increasing the habitat for insects and many other critters.
Slowing down to plant speed
But before we can begin thinking about habitat improvement, we need to try to understand what’s already here. So today I’m surveying this rocky hilltop, roughly the area of a modestly large American house and its lawn. This project is especially interesting because, for the most part, this grassland already appears to be in very good condition. If we were starting with a flat lawn or a field of knapweed, the addition of any native plants would boost the habitat value tremendously. But in this case, we are entering into a conversation with a plant community that is already diverse. What can we learn from what is already here? Are there missing species that might add to the habitat value of this community? Can we help this grassland thrive even more?
Today is the beginning: meeting-the-plants day. As an active, easily-distracted mammal, I find it hard to comprehend this hilltop from a plant’s perspective. Fortunately, I have some locals to ask. These plants are out here on this hill every day of the year, whether they like it or not. They carry the wisdom of millions of years of evolutionary history in their stems. If only they spoke English, I’d be out of a job. As it is, learning from them is going to take patience and some imagination. For a few hours, we’ll have to try to slow down to the speed of a plant.
Up close, the grassland is an intricate pattern of shape and color. Here, a thin crowd of bluebunch wheatgrass (Agropyron spicatum) surrounds me. They become dense and continuous on the moister north slope below me, where their accumulation of dead stems thatches the earth among Douglas-firs. But in this rocky fabric on top, they are much more scattered. Their slender clumps tower above the compact cushion plants hugging the limestone.
It looks like a tended rock garden up here – and it’s in full bloom. Yellows, whites, and purples are the colors of the season. These flowers aren’t here for our eyes. They’re flashy billboards for bees, flies, and other pollinators: “nectar here!” But it’s cloudy today, and a chilly breeze discourages the insects. For the most part, the flowers are waiting for a warmer day to get pollinated.
A diversity of yellow
The wild parsley (Musineon divaricatum) is just finishing its bloom period. It grows scattered, a plant here and there, the deep taproots anchoring the slightly rough green leaves. As the flowers fade, the leaves are losing vitality, too. It appears that this plant’s strategy is to capitalize on the moist spring, set seed early, and retreat underground for the hot summer ahead.
Three yellow asters are flowering today. What’s that on the woolly groundsel flowers (Senecio canus)? Tiny insects are crawling all over them. They’re dark and long-bodied with narrow wings: thrips. What are they doing here?
Researching them later, I find that thrips (Thysanoptera) can be common on flowers, where they feed on nectar and pollen. In spite of their diminutive size, they have been documented pollinating a wide range of plants. Maybe the groundsel doesn’t need a warmer day to set seed.
A hairy covering
The leaves of the groundsel are covered in white felt. Why? Is this a blanket against the wind, holding precious moisture and warmth? Not exactly, it turns out. Studying this question in Sonoran Desert plants, James Ehleringer found that whitish leaf hairs are great at reflecting sunlight. These hairs actually cool the leaves substantially. This reduces moisture loss, allowing plants to continue growing longer during droughts.
The four-nerved daisy (Tetraneuris acaulis) looks a bit similar, but its leaves have pointier tips and silkier hairs. And while the groundsel’s flowerheads grow in branched arrays, four-nerved daisy heads are solitary. There are thrips crawling over these flowers, too.
Old and young
The four-nerved daisies range in size, from large cushions with numerous blooms to tiny clusters of leaves without any flowers. Are the smallest plants last year’s seedlings? It seems possible, though we won’t know for sure until we germinate some seeds and watch them grow.
A third yellow aster is just coming into bloom. This is stemless goldenweed (Stenotus acaulis), a cushion-former with deep green, spear-like leaves. The leaves look succulent at a distance, but close-up they are minutely roughened. The goldenweed grows very scattered here. Most of these plants are large cushions with dozens of flowering stems. I find only a few smaller clumps. Unlike the four-nerved daisy, none of these are small enough to be recent seedlings. Is the goldenweed more sporadic in its germination? Does it need an unusual combination of weather conditions to sprout, conditions that only occur here in certain years?
Purple and sticky
Among all of these flowers, the large purple tubes of the fuzzy-tongue penstemon (Penstemon eriantherus) catch my eye. They catch the eye of a large, fuzzy bee as well. It enters one flower, takes off noisily, and crawls into another just a foot from where I’m standing. I bend down, hoping for photos, but the bee is already flying again. It circles me twice and then it’s gone.
These flowers are intricate. Thin purple lines draw my eye inward, past the hairy yellow staminode, toward the waiting anthers and stigma. Would this flower be even more striking with a bee’s ultraviolet vision?
The inside of the flower is smooth, but the outside is covered with sticky glands. Why the glands? Is this a defense against herbivores? Again, I turn to published studies in the search for an answer. Patricia Thomas studied this question in the 1980s with a related midwestern species, Penstemon digitalis. Over several years, she experimentally covered the glands of some flowers with talcum powder, leaving others undisturbed. Would herbivorous insects swarm the flowers whose sticky defenses had been removed?
Surprisingly, she found, they did not. The insects were actually a bit more abundant on the flowers with sticky glands. They either managed to feed on the flowers while avoiding the glands entirely, or they groomed themselves after making brief contact. So why do these penstemons cover their flowers in plant glue? No one knows. At least for Penstemon digitalis, if these glands are a response to herbivores, the insects seem to be one step ahead.
The community among the rocks
Leaving aside the mystery of the glandular flowers, I look around. The fuzzy-tongue penstemon is common in the rockiest areas of the hilltop. I see a range of sizes: mature plants laden with flowers, medium-sized leaf clusters, and small rosettes that presumably represent seedlings. Growing with the penstemons are a variety of ground-hugging natives. Mats of white-margin phlox (Phlox albomarginata) are putting their energy into green fruit capsules, while the last few flowers remain. Hood’s phlox (Phlox hoodii) bloomed earlier. Now they’re just unassuming, spiky green cushions. The Sandberg bluegrass (Poa secunda), bunchgrasses in miniature, are extending their easy-to-miss flowers above their inch-long leaves. Unlike the yellow asters and the purple penstemons, the bluegrass clumps don’t need to attract pollinators. The wind carries their pollen.
This is a diverse community, made up almost entirely of native plants. Over 30 species are growing in the space a small house would take up. The only notable immigrant right here is pale alyssum (Alyssum alyssoides), a tiny annual whose native range stretches from Europe into Asia and Africa. At least ten native plants are flowering today. Pallid Indian paintbrush (Castilleja pallescens) is in full bloom. Cutleaf fleabane (Erigeron compositus) is sporting white rays and the first fluffy parachutes of its wind-dispersed seeds. Here and there are the little white umbels of textile onion (Allium textile).
From diverse to simple
Twenty yards west, the community changes suddenly. The aspect shifts from barely south-facing to slightly north-facing. Moss cover increases substantially. The rocky ground is the same: bits and pieces of ancient limestones and muds, deposited in the Belt Sea before plants existed. But in place of the diverse community to the east, this area is dominated by a single plant. It’s a slender grass, its burgundy flower heads nodding in the wind.
This is cheatgrass (Bromus tectorum) – named, I have heard, by ranchers who blamed it for “cheating” them out of good forage grasses. Native to parts of Europe, Asia, and Africa, it first appeared in Montana in 1898. People generally despise it – and I confess that sometimes I do too. But as a biologist, I am trained to observe, not to hate. What can this patch of cheatgrass tell us? Why is it here? And why is it not 20 yards over there?
Get rich quick
Cheatgrass is an annual. While perennials tolerate the intense summer drought by investing in deep roots, going dormant, or reflecting sunlight with dense white hairs, cheatgrass uses a “get rich quick” strategy. It sprouts very early in the spring – or even the fall before, if we get enough rain. When the snow melts, it grows fast, before the soil dries out. Soon it will flower and pour all of its energy into seed production. By July it will be dead and tinder-dry. Its awned seeds will stick in socks and hitch rides on animals, passively seeking out new places to grow. When the moisture returns, the seeds will start the cycle again.
Why here and not there? In this case, I really don’t know. I often see cheatgrass along roadsides and in overgrazed pastures: soil disturbance is an annual’s friend. But here, the abundance of mosses suggests that this soil has not been heavily disturbed. Marisa points out that she has seen elk bedding down in this area. Maybe their hooves have churned the ground enough to give cheatgrass a foothold.
In any case, this area presents an opportunity for habitat improvement. The cheatgrass is not growing alone here; there are already scattered natives alongside it. This area is dotted with broom snakeweed (Gutierrezia sarothrae) and hairy goldenaster (Heterotheca villosa), both yellow flowers that will bloom later in the season. Hood’s phlox, white-margin phlox, and fringed sage (Artemisia frigida) are also present. And ten yards farther west, on the same exposure, the vegetation shifts back to a native community dominated by cutleaf fleabane, Sandberg bluegrass, and mosses.
The diversity present on this single hilltop amazes me. And the patterns – cheatgrass here, cushion plants there – challenge my understanding. Already, after slowing down to plant speed for just a few hours, it’s clear that there’s more going on here than I will ever understand.
What about habitat improvement? Clearly the cheatgrass stand provides an opportunity to try adding some more native plants. Just to the north of it, a scattered patch of spotted knapweed (Centaurea stoebe) provides another opportunity. The native plants already growing here give us a list of species that we know are well-suited for these conditions. Are there others that might be good additions?
With this project, we have some latitude to experiment. I can already think of a few plants we might try adding: bitterroot (Lewisia rediviva), prairie clovers (Dalea spp.), and Missouri goldenrod (Solidago missouriensis) come to mind. Throughout the summer, I’ll be keeping my eyes open when I’m in similar habitats, brainstorming plants we might try.
How will we try adding plants to this community? The plants already here are far too important to lose, so large-scale soil disturbance is out of the question. Instead, we’re looking at germinating seeds in pots and transplanting seedlings without disturbing the existing natives.
I’ll be revisiting this project on the blog as it progresses. In the meanwhile, I’d love to hear from you! Have you found ways to augment native plants around your house? What are your observations of cheatgrass? I’ve posted yesterday’s full species list here, along with the start of a list of possible additions. Do you have a species to suggest? Please leave a comment here, or contact me!
Will any of this work? I have absolutely no idea. These plants have been here every day for years – I’ve just spent a single day looking around. In either case, undoubtedly the plants will teach us something.
Brummer, T.J., Taylor, K.T., Rotella, J., Maxwell, B.D., Rew, L.J., & Lavin, M. (2016). Drivers of Bromus tectorum abundance in the western North American sagebrush steppe. Ecosystems 19:986-1000. https://scholarworks.montana.edu/xmlui/bitstream/handle/1/12644/Lavin_Ecosystems_2016.pdf?sequence=1&isAllowed=y
Lavin, M., Brummer, T.J., Quire, R., Maxwell, B.D., & Rew, L.J. (2013). Physical disturbance shapes vascular plant diversity more profoundly than fire in the sagebrush steppe of southeastern Idaho, U.S.A. Ecology and Evolution 3(6):1626-1641. https://onlinelibrary.wiley.com/doi/10.1002/ece3.574