Wildflowers on the trail to Cross Mountain, between Telluride and Rico. The 7.2-mile hike is strenuous, but rewards those who complete it with solitude and rare blooms.

Courtesy of Chris Kassar

Wildflowers put on a special show in Colorado each year. Soon, a cast of about 3,000 species will start appearing in mountain valleys, on urban hillsides and across the Eastern Plains. Outdoor writer and biologist Chris Kassar documented the best hikes in the state to see wildflowers in a book for Falcon Guides.

Here are Kassar's 10 top trails to view summer blooms:

Green Mountain-Onahu Loop

What To Expect: This 8-mile, moderately difficult loop takes off from the west side of Rocky Mountain National Park.

What You'll See: The trail climbs though tranquil forests teeming with flowers and includes a visit to Big Meadows. Classic Colorado wildflowers are abundant here – columbine, sunflower, paintbrush and wild rose – along with many lesser known blooms.

When To Go: Peak bloom is late June to July

Cathedral Lakes

What To Expect: This 6-mile climb west of Aspen is considered strenuous because of steep climbs and altitude.

What You'll See: A breathtaking amphitheater surrounded by craggy granite ridges and toothed summits. The long list of flowers to be found here includes yarrow, golden aster, two kinds of pussytoes and Whipple’s penstemon.

When To Go: Peak time for blooms is mid-July to mid-August.

Aspen To Crested Butte Via West Maroon Pass

What To Expect: This hike is 11.6 miles long, takes six to 10 hours to complete and requires a shuttle.

What You'll See: The head-high wildflowers, jagged summits, alpine lakes and pine-covered valleys make lung-busting effort well worth it. Flowers commonly found include showy daisy, thimbleberry, shrubby cinquefoil, elephant heads and death camas.

When To Go: Peak blooms are on show mid-July to early August.

Rustler Gulch North Of Crested Butte

What To Expect: This trail is 9.4 miles out and back, but it is considered a moderate hike because of smooth terrain and only a moderate elevation gain.

Wildflowers bloom near Crested Butte.

CPR News/Anna Hanel

What You'll See: Along the trail is a mind-blowing plethora of fragrant head-high blooms. Expect to see more than 100 species, including mountain bluebells, rosy paintbrush, heartleaf arnica and king’s crown.

When To Go: Peak blooms are mid-July to mid-August.

Copley Lake

What To Expect: This trail is 3.9 miles long and takes off west of Crested Butte on Kebler Pass. You may share the trail with equestrians and mountain bikers.

What You'll See: Copley Lake offers amazing arrays of rainbow blossoms in a climb that ends with phenomenal views at the lake. There will be plenty of color in scarlet gilia, mountain harebell, orange sneezeweed and wild strawberry, among others.

When To Go: Peak blooms are in July.

American Basin near Lake City

What To Expect: This hike itself is short and easy – 2.1 miles out and back. But getting to it is the tough part. The trailhead is about a 25-mile drive from Lake City, mostly on dirt roads.

What You'll See: Hikers will enjoy a rushing creek, an intense waterfall and breathtaking views of craggy vertical peaks. Wildflowers will include yellow monkeyflower, snow lover, yarrow, mountain bluebells and tall larkspur.

When To Go: Peak blooms are mid-July to early August.

Cross Mountain Via Lizard Head Pass

What To Expect: This strenuous 7.2-mile trail starts just south of Lizard Head Pass between Telluride and Rico.

What You'll See: After winding through cool, dense evergreen forest, hikers reach the base of Lizard Head Peak. Enjoy the solitude there, as well as jaw-dropping wildflowers such as corn lily, edible valerian, monument plant and rattlesnake plantain orchids.

When To Go: Look for peak blooms mid-July to mid-August.

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Ice Lakes

What To Expect: This 8.6-mile out-and-back hike in the San Juan National Forest northwest of Silverton is strenuous due to distance, altitude, elevation gain and steep sections. The trail to Ice Lakes takes off from the South Mineral Campground.

What You'll See: Hikers climb through tranquil meadows and end above treeline at turquoise pools set against rugged cliffs. Expect to find dozens of varieties of blooms. including wild rose, parrot’s beak, showy daisy, sky pilot and old man of the mountains.

When To Go: Peak bloom time is late July to mid-August.

Ouzel Falls

What To Expect: This 5.4-mile trail in Rocky Mountain National Park’s wild basin can be steep, rocky and rugged in places.

What You'll See: The wildflower display -- white bog orchids, mouse-eared chickweed and kinnikinnick -- comes with beautiful river-valley scenery, including three waterfalls.

When To Go: Expect to see the most blooms early to mid-July.

Pawnee Buttes

What To Expect: This peaceful 4-mile meander on the eastern plains reaches two giant sandcastle-like rock formations east of Fort Collins.

What You'll See: The hike snakes through badlands and arroyos and past rugged cliffs. Colorful blooms, including prickly pear cactus, mountain cat’s eye and lavender-leaf sundrops, stand out in sharp contrast to the severe landscape.

When To Go: Peak blooms are mid-May to early June.