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Mushrooms of the Rocky Mountain Region: Habitats and fruiting times

by Timber Press on February 29, 2016

in Food

This Rocky Moutain representative of the Boletes edulis complex has recently been recognized as B. rubriceps.

This Rocky Moutain representative of the Boletes edulis complex has recently been recognized as B. rubriceps. Image: Karen Ruth Evenson

From Mushrooms of the Rocky Mountain Region, an introduction to where and when to find the region’s most interesting and ecologically important mushrooms.

The Rocky Mountains rise out of the prairies and plains of western North America to elevations of more than 14,000 feet in Colorado, creating a diverse terrain that ranges from shortgrass prairies to dense forests to treeless alpine tundra. Such varied habitats allow for an overwhelming degree of biodiversity, or diversity of life, to exist in the region. The mushroom flora is no exception, exhibiting an amazing variety of species from many distinct habitats.

Ecosystems of the Southern Rocky Mountain Region

Like birds, mammals, plants, and soils, mushrooms are an integral part of every ecosystem in the Rocky Mountains. An ecosystem is a recognizable grouping of plants, animals, environmental conditions, and the interactions among them. A simplified classification of the major ecosystems of the region is portrayed in this map.


Ecosystems of the southern Rocky Mountain region including Colorado and parts of Wyoming, Utah, and New Mexico.


Although the grassy plains and prairies appear flat, they really slope gently eastward from the Rocky Mountain uplift. They cover great proportions of many states in the region, forming massive nearly treeless grasslands. Most grassland elevations are below 5500 feet but some mountain grasslands occur at altitudes up to 8000 feet, examples of which are Colorado’s North Park, Middle Park, and South Park areas. The eastern third of Colorado, the eastern half of Wyoming, huge areas in eastern New Mexico, and significant areas of Utah are rolling grasslands.

Here the combination of precipitation, temperature, and soil conditions is not suitable for tree growth, but a wealth of grasses and prairie flowers flourishes. Without the presence of trees, grasslands do not have the variety of mushroom species found in other ecosystems. Mushroom fruitings in these regions are as sporadic as the rainfall and as unpredictable as a sudden spring blizzard. However, huge puffballs are common such as Calvatia cyathiformis, which has been found as giant fairy rings reported to be centuries old. Other saprobes such as Marasmius oreades (fairy ring mushroom) are also often found in grazed and irrigated fields, which now occupy much of the former prairie. Other grassland mushrooms include species of Coprinus, Panaeolus, and Stropharia, which break down grasses, animal dung, and other organic materials.

Calvatia booniana (giant western puffball) in a grassy pasture. Image: Vera Stucky Evenson

Calvatia booniana (giant western puffball) in a grassy pasture. Image: Vera Stucky Evenson

Semidesert Shrublands

Dominated by rabbitbrush, sagebrush, greasewood, and saltbush, semidesert shrublands are most commonly found along drainages in the prairie and plateau regions of many areas in the Rocky Mountain region. Often called cool deserts, semidesert shrublands experience extremes of intense sunbaked heat in the summer, frigid cold in the winter, and arid conditions all year long. Like the shrubs and grasses that share the loose sandy soil, fungi are able to eke out just enough moisture from winter snows and an occasional summer  thunderstorm to fruit sporadically here. Many of the same mushroom species found in the grasslands also thrive in these shrublands. The large fruiting bodies of Calvatia booniana (giant western puffball) can occasionally be found lying like huge overgrown eggs among the grasses and sagebrush.

Pinyon-Juniper Woodlands

Rising somewhat higher than the semidesert shrublands, pinyon pine and juniper woodlands form huge sprawling evergreen forests in many parts of the Rocky Mountains. Often called pygmy forests because of the short stature of the trees, pinyon-juniper woodlands are typically not quite as hot or as dry as the regions below them.

These woodlands are found in small but significant parts of Utah, large areas in western and southern Colorado (as well as an isolated forest of pinyon pines in a more never plentiful,  mycorrhizal species of Boletus, Leccinum, and Suillus, a group commonly known as boletes, as well as Russula and Lactarius species can be found in these areas after heavy rainfall. Tulostoma species (stalked puffballs) fruit in the poor soil here along with tiny species of Crucibulum and Cyathus (bird’s nest fungi) that sometimes form clusters of Lilliputian nests (or splash cups) and eggs (spore cases) on deadwood or dung. The splash cups aid these recyclers in spore dispersal during rainstorms.

Rhizopogon species, hypogeous fungi (fruiting underground), are characteristic inhabitants of this land. Their fragrant nutlike fruiting bodies serve as an important food source for the small mammals that can detect their odors and dig them up.

Cyathus stercoreus, one of the bird's nest fungi, known as dung-loving bird's nest. Image: Vera Stucky Evenson

Cyathus stercoreus, one of the bird’s nest fungi, known as dung-loving bird’s nest. Image: Vera Stucky Evenson

Riparian Lands

Rocky Mountain rivers, streams, lakes, ponds, and marshes provide much needed moisture to a thirsty land. Vegetation in riparian lands (meaning “adjacent to water”) often contrasts dramatically with that in the much drier landscapes nearby. In lower elevations, cottonwoods and willows are lacy indicators of water nearby, whereas mountain riparian ecosystems feature subalpine bogs, rushing streamsides, and high mountain lakesides. Conditions in riparian lands encourage the growth of hundreds of species of higher fungi. Most of them are mycorrhizal fungi living symbiotically with cottonwoods, willows, and alder, and at the higher altitudes, conifers and aspens.

Rocky Mountain riparian lands in lower elevations are the best places to find the elusive common morel, Morchella esculentoides, which fruits here under cottonwoods in the spring along with many delicate cup fungi. In higher elevations, riparian ecosystems feature conifers and aspens along bogs, streams, and lakes. Look for clusters of Pleurotus populinus during moist weather growing in shelving masses on aspens. Other common riparian mushrooms include Lactarius deliciosus and L. montanus, Laccaria laccata, and Suillus brevipes. Wood-inhabiting polypores are commonly found here in the spring and summer. At the end of the season in late fall in dried up riverbeds of prairie land, masses of fruiting bodies of Tricholoma populinum (sand mushroom) emerge from the sandy soil under cottonwoods where foraging deer seek them by pawing under the already fallen leaf litter

Montane Shrublands

As the land rises to altitudes of 5500 to 10,000 feet into the foothills and mountains, the coarse soils support the growth of dense-to-sparse discontinuous belts of deciduous shrubs such as mountain mahogany, sumac, and Gambel oak. Hot in the summers and very cold in the winters, montane shrublands are too arid to support full-sized trees and their associated mycorrhizal fungi. The limited but interesting mushrooms native in these elevations include several kinds of hypogeous fungi that have evolved an underground lifestyle to withstand the rigorous climate. Gasteroid fungi such as the true puffballs, species of Lycoperdon and Calvatia, may be visible on the soil surface. The beautiful earthstars of the genus Geastrum are sometimes common here. Rotters of Gambel oak can also be found, such as Polyporus arcularius. Occasionally decomposers in the genera Coprinus, Agaricus, and Agrocybe fruit after moisture saturates the loose soil.

A cluster of aspen-loving Pleurotus populinus. Image: Vera Stucky Evenson

A cluster of aspen-loving Pleurotus populinus. Image: Vera Stucky Evenson

Montane Forests

This type of ecosystem occurs at elevations between 5500 and 9000 feet. The characteristic tree species are pines, both ponderosa and lodgepole, which are interspersed with groves of aspen and scattered with stands of Douglas-fir, especially on north-facing slopes. Meadows abundant with grasses and wild flowers, densely forested north-facing slopes, and more open south-facing slopes provide both dry and moist environments—a great variety of habitats for fungi. Mushrooms of all forms abound here throughout the collecting season, which begins when the snow melts in April and May and ends about mid-September when the snows again cover the leafy debris.

Because of the predominance of conifers, all of which depend upon mycorrhizal fungi, there can be great fruitings of boletes such as the delectable Boletus barrowsii and the common sticky-capped Suillus brevipes, tiny umbrella Mycena species, goblet-shaped clitocybes, and pinkish-gilled Laccaria. Here varicolored waxy-capped Hygrophorus species peek out from the needle duff, the much sought-after Tricholoma magnivelare (white matsutake) erupts from lodgepole pine needles in the fall, and a rainbow of colorful Cortinarius, Russula, and Lactarius species decorate the forest floor.

Wood-rotters such as the tiny garlicky Marasmius thujinus are busy recycling fallen leaf litter, and the distinct forms of polypores such as Ganoderma applanatum (artist’s fungus) decorate aspen logs. Near the shady forest edge, softball-sized puffballs such as Calbovista subsculpta sometimes can be found.

One of the most exotic-looking fungi in the Rocky Mountain region thrives here. The bright red-orange Amanita muscaria (fly agaric) always gets attention because of its gaudy colors, evoking fairy tales, witches’ brews, and primitive and modern psychoactive rituals. In spring and early summer, the popular Morchella brunnea (black morel) can occasionally be found among the conifers, amazingly camouflaged to resemble wet pine cones scattered about the shadows.

Snowbank mushroom habitat. Image: Kenneth M. Evenson

Snowbank mushroom habitat. Image: Kenneth M. Evenson

Subalpine Forests

As the mountains rise above 9000 feet, the dark rich subalpine forest of spruce, subalpine fir, bristlecone pine, and aspen reigns supreme. Like the montane forests below, the subalpine forests have diverse vegetation, depending upon the steepness of the slope and the exposure to the sun and weather. However, the temperatures are cooler, the moisture greater, and the snow cover lasts longer. Many kinds of mushrooms flourish here too but the season is short.

In the spring and early summer look for snowbank mushrooms such as the bright orange cups of Caloscypha fulgens fruiting at the edge of melting snowbanks. The sun’s intense energy reflects off the glistening snow and provides localized warmth. When combined with almost 100 percent humidity, these conditions encourage the growth of a few species of hardy fungi such as flattened cup-shaped Discina perlata and the jelly fungus Guepiniopsis alpina, which hangs like tiny orange gumdrops on dead conifer twigs. Giant “brain fungi,” Gyromitra montana, may be found nearby as well as the cold-loving, silvery-colored gilled fungus, Clitocybe glacialis.

True to its specific epithet, Hygrophorus subalpinus fruits in this forest, as do many species of Galerina, especially the dangerously poisonous wood-inhabiting G. marginata. Look for gloriously colored ramarias (the corals of the forest), tiny fairy-fingered Alloclavaria purpurea, red-staining Agaricus amicosus and yellow-staining A. silvicola, and members of the huge family Cortinariaceae, which form mycorrhizal associations with nearly every kind of tree here.

Caloscypha fulgens in subalpine habitat. Image: Vera Stucky Evenson

Caloscypha fulgens in subalpine habitat. Image: Vera Stucky Evenson

Alpine Tundra

As you climb out above the forest, you reach a boundary known as tree line. Here the rocky land mass thrusts upward so high that conditions become too cold, dry, and windy for trees to grow. However, such adversities do not stop fungal growth entirely and certainly do not inhibit the lichens from clinging to rocks. Right at the edge of the alpine tundra, which is defined as the land above the trees, dwarf willows and krummholz (stunted and twisted conifers) live with their fungal partners. The plants survive in these harsh conditions by forming mycorrhizal unions with fungi such as alpine Cortinarius, Hebeloma, and Inocybe species. Occasional fruitings of saprobic puffballs, Calvatia species, leave their “footprints” in the low tundra as dried vase-shaped remains of the once-rounded spheres.

Fruiting Times

Two important factors are needed for conditions to be right for mushrooms to begin fruiting: increasing temperatures and moisture. Often the very best time to find mushrooms is about a week after a warm dry spell has been abruptly ended by a heavy downpour or a few days of afternoon rains. The eager mushroomer’s best reward for enduring hot dry weather is the joy of the “blooming” of the mushroom flora in a favorite habitat when moisture comes again.

The mushroom season in the Rocky Mountain region generally lasts from mid-April to the end of September. At higher elevations it is the short span of time between spring weather warm enough to melt the snowpack and the return of frigid conditions and snow in early fall. Some years a delightful warm spell in March or early April produces flushes of early fruiting mushrooms such as Agrocybe praecox, Pleurotus pulmonarius, or Peziza repanda along the rivers that flow eastward and south through the region’s prairies. Cottonwood groves along these riparian areas are interesting places to spend some pleasant hours looking for spring fungi, flowers, and wild asparagus.

Hydnum repandum (hedgehog mushroom), fruiting in late August in upper montane to subalpine ecosystems. Image: Vera Stucky Evenson

Hydnum repandum (hedgehog mushroom), fruiting in late August in upper montane to subalpine ecosystems. Image: Vera Stucky Evenson

In the fall continued warm weather or a late first frost makes excellent mushrooming possible in some habitats into early October. Local mushroomers generally consider late July until early September to be the most productive season in the montane and subalpine habitats, with August being the peak.

In the Rocky Mountain region where large elevation changes occur within short distances, mushroom enthusiasts can extend the season simply by traveling to another elevation. If your favorite mushroom—say, a member of the Pleurotus pulmonarius group—produces abundantly in April and May at lower elevations, keep watching for it or a close relative, P. populinus, at higher elevations as spring changes to summer. You can essentially chase spring up the mountains!

The high country may still be covered with snow when mushrooms like Morchella esculentoides (common morel) are fruiting in May along the rivers below 5000 feet. Then, when the plains begin to dry up in early summer, the warming air and moist snowmelt conditions of the montane and subalpine ecosystems begin to stir the mycelium into producing a great succession of mushrooms, such as Cantharellus cibarius (golden chanterelle) and many species of Agaricus.

The fruiting of large quantities of the mushrooms favored by many collectors is usually dependent on the depth of the winter snowpack and, more importantly, the rain that comes as thunderstorms during the summer and early fall. If that rain soaks down into the soil and the late summer sun warms the earth, then conditions are ripe for a bountiful fruiting of mushrooms.


evenson_vVera Stucky Evenson is curator of the Sam Mitchel Herbarium of Fungi at Denver Botanic Gardens. She collects and studies thousands of specimens and photographs of native mushrooms in many ecosystems, including those that grow in city environments. She is a past president of the Colorado Mycological Society. In 2008, Vera received the North American Mycological Association’s award for contributions to amateur mycology in honor of her three decades of dedication and expertise in the field. She holds a bachelor’s degree in botany and bacteriology and a master’s degree in microbiology.


Denver Botanic Gardens 02Green inside and out, Denver Botanic Gardens began in 1951 and is considered one of the top botanical gardens in the United States and a pioneer in water conservation. Accredited by the American Alliance of Museums, the Gardens’ living collections encompass specimens from the tropics to the tundra, showcasing a plant palette chosen to thrive in Colorado’s semiarid climate. It includes the Sam Mitchel Herbarium of Fungi, the largest and best curated mycological collection of the southern Rocky Mountain region. The Gardens offer world-class art exhibitions, education programs and important plant conservation and research initiatives.


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For mushroom hunters, hikers, nature lovers, and more.

1 Michelle Wright December 9, 2016 at 10:03 pm

Just a question for a project my grandson is doing for science in school. He is in 6th grade. Do any mushrooms grow above the tree line in the Colorado Rockies? He is looking for decomposers in the food chain. We know lichen can be decomposers but he is looking for others that can withstand this harsh climate.

Thank you so much

2 Christopher October 4, 2018 at 1:05 pm

I need that map showing the ecosystems of the southern Rocky Mountain region in your article “Mushrooms of the Rocky Mountain Region: Habitats and fruiting times”. Would you kindly tell me your source? Thank you.

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