When Danielle Reyes cues her students to reach up to the sky, they really can.

Before starting class, yoga instructor Danielle Reyes is sure to share this pearl of wisdom with her students: “Look down and make sure your hands won’t touch anything sharp or unpleasant.”

That’s because instead of standing on a wood floor, the group is on top of grass, dirt and twigs — and possibly some surprises. The scenery is always changing on Yoga Hikes, which Reyes launched this spring to give Washingtonians a different way to experience nature.

“I’m an ambassador for green spaces,” says Reyes, who relies on her knowledge of D.C.’s network of parks and trails to develop routes for her classes. Half of each 90-minute session is devoted to a yoga practice, but students are never stuck in one place for more than 15 minutes. In between stops, they hoof it at a quick clip, elevating their heart rates and thinking about their alignment.

“You’re going to start thinking, ‘I should walk to the Metro like this all of the time,’ ” Reyes promised a half dozen disciples on an urban hike last week. They had gathered in Dupont Circle, where they’d started the yoga practice with a warm-up focused on breathing and centering. Welcome the noise, Reyes said, noting that real life requires learning to quiet the mind amid the sounds of the city.

And soon they were off on their first trek and facing an uphill climb. Reyes was ready with pointers.

“Imagine someone’s hands are on your glutes, pushing you forward,” she said. “Preferably someone you like.”

Ascending Kalorama’s Spanish Steps, Sarah Campbell, 31, looked around in awe.

“I’ve never seen this before,” said the Columbia Heights resident, who’s also enjoyed a nature hike with Reyes in Rock Creek Park. “This feels how yoga should be. You might have mud on your shoes and you don’t care. You’re not so precious about it.”

You might also have dogs running under your downward facing dogs. That’s what happened when the group paused in nearby Mitchell Park. Animals have a tendency to want to join in on the flow, Reyes said, although they’re not expected to hold chair pose or stay in a lunge for several minutes during a warrior series.

Reyes likes to keep the power vinyasa challenging because students can recover while they hike. She expects students to pick a pace and stick with it, but it’s always walking — never running.

No one is too out of breath to talk, which makes the classes conducive to socializing. Reyes says she’s hiked with lots of couples on double dates and groups of friends looking for a way to catch up.

Danielle Reyes, far right, totes along miniature yoga mats so students don’t have to get their hands too muddy.

Marcia Maziarz, 52, went on last week’s hike with her 15-year-old daughter, and the duo plan to arrange more mother-daughter outings over the fall. “It’s hard to find things teens can do,” the Woodley Park resident said.

Anyone in shape enough to walk a few miles can participate in Yoga Hikes, Reyes says. There’s no need to have yoga experience, she adds, just a desire to see the city in a new way.

Take a Hike

It’s $25 to drop in for a Yoga Hike; there are discounts for buying multi-hike packages. Here are a few upcoming outings. You can find the full schedule at yogahikesdc.com.

–Urban hike on Thursday at 6 p.m. Visit three city parks, starting in Dupont.

–Nature hike from Woodley Park on Saturday at 10 a.m. and noon. The route includes Rock Creek, Dumbarton Oaks and Montrose parks.

–Nature hike on Sunday at 10 a.m. Start and end at Peirce Mill in Rock Creek Park.