The hills are alive with colorful bursts of wildflowers, marking the return of the annual Sunol Spring Wildflower Festival and an abundance of flora and fauna at Mt. Diablo State Park, where tours will be held later this month.

The mountain is putting on a stellar show this spring.

"The poppies on the north gate side are incredible. There are patches that seem like you're walking through the poppy field in the Wizard of Oz. It's gorgeous." said Ranger Dan Golde.

The Sunol festival, to be held at Sunol-Ohlone Regional Wilderness from 11 a.m. to 4 p.m. Saturday offers wildflower hikes and other family-friendly events.

Horseback riders move past some California poppies along a trail at Sunol-Ohlone Regional Wilderness area in Sunol, Calif. on Sunday, April 6, 2014. The
Horseback riders move past some California poppies along a trail at Sunol-Ohlone Regional Wilderness area in Sunol, Calif. on Sunday, April 6, 2014. The park is hosting the Spring Wildflower Festival on Saturday, April 12, 2014 from 11am to 4pm. (Jim Stevens/Bay Area News Group)

"One of my goals is to introduce people to this very, very special place," naturalist Cat Taylor said. "This park is absolutely beautiful. It's amazing that we have so many millions of people in the Bay Area and to have this wilderness right on the edge of this urban fringe."

Naturalists have been studying the region's wildflowers for more than 50 years, keeping track of peak bloom times, she noted.

"People always ask when the wildflowers are blooming," Taylor said. "It always seemed to peak around the second week of April, so that seemed to be the best time to put on the festival."

The regional park has a unique geology that makes the area ripe for brilliant displays of wildflowers.

"We are along the Calaveras Fault line," Taylor explained. "Along fault lines, we are going to get a lot of serpentine (rock and soil) outcrops. It makes it so that non-native wildflowers and grasses don't grow well there. You only get these pure stands of native wildflowers." "You'll be standing on a hillside that's completely pink and purple and looking across at a hillside that's completely yellow," she added. "You'll know those are the serpentine outcrops."

Hikes will be offered throughout the day, including a butterfly walk and a wildflower sketch hike. Hikers on the ethnobotany route will learn about the many uses for plants. The longest trek, 3 miles round-trip, takes hikers to the park's famed Little Yosemite area.

"We offer a number of hikes, everything from preschoolers to long hikes," Taylor said. "Everybody gets something."

State Sen. Ellen Corbett will host her seventh annual Walking Town Hall at noon on event day. The senator will give an update on important state and East Bay environmental issues and have a brief discussion. After that, Corbett and hikers will take a guided tour through the park.

The band Extended Roots will play bluegrass throughout the day. A variety of exhibitors and vendors will provide information and sell local goods, such as olive oil and honey.

"We have something for everybody," Taylor noted. "Families come out, and there are so many things for the kids to do with crafts and hikes. People who want to experience the wildflowers with a guide will learn more about the area."

Hikers can enjoy the wildflowers on Mount Diablo at any time, but docent-led hikes will be offered April 26-27 from 10 a.m. to 4 p.m. as part of Celebrate on the Mountain.

"Spring is a wonderful time to come out," said Ranger Dan Golde. Last fall's extensive Morgan Territory fire that blazed through 3,111 acres on the mountain's south side will lead to an unprecedented burst of color on the mountain this spring.

"Due to the recent fire, it's going to produce some flowers that haven't been seen on the mountain for decades," Golde said. "The fire allows some of the plants that have been dormant to drop their seeds and enables them to sprout and grow."

The long-awaited rains have also prompted wildflowers to finally bloom, he noted.

"Due to the rains, we've had some flowers coming out -- the lupine, the golden poppy," Golde said.

"There are some other flowers, like the painted brush over by the Rock City area. This is a good time for people to start coming up and viewing the flowers."

For more information about Celebration on the Mountain visit http://bit.ly/1jKmD5y.

The Sunol Spring Wildflower Festival is free, but parking is $5. Parking is limited and carpooling is recommended. No food will be sold at the event. For details, call 510-544-3249 or email svisit@ebparks.org. Sunol-Ohlone Regional Wilderness is at the end of Geary Road off Calaveras Road, five miles south of Interstate 680 and the town of Sunol. At the bottom of the Calaveras Road off-ramp from southbound I-680, turn left on Calaveras Road.

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