Near the base of a roughly 25-foot tall pyramid of heirloom squash, Carl Franklin Jones Tuesday afternoon meticulously carved with a small knife the pale flesh of a watermelon, cutting away the green skin to reveal flowers ringed by ivy leaves.

The 60-year-old Tennessee man took part in Santa Rosa’s National Heirloom Expo for the second year, delighting attendees with the artistic venture he’s spent the last 13 years perfecting. Among his creations showcased at the Sonoma County Fairgrounds’ Hall of Flowers were oranges with silly faces and a pumpkin etched with an intricate, maze-like design.

“People ask ‘why are you here and why do you do this?’” he said as onlookers marveled at his work. “I do this because it makes people happy.”

Celebration and learning were at the heart of the 8th annual festival, which organizers expect will draw this year as many as 25,000 attendees over its three-day run that ends Thursday. It features more than 4,000 varieties of heirloom produce, more than 200 vendors and about 100 speakers addressing topics ranging from pollination to cannabis.

Displays ranged from whimsical arrangements of gourds that resembled Stonehenge to a table of more than 30 varieties of peppers grown from heirloom seeds that Santa Rosa resident Ubaldo Solorio collected from around the globe. The selection from his home garden included a handful of Carolina Reapers, a wrinkly, red pepper he said is the hottest in the world.

Growing the vegetables from heirloom seeds — ones that have been handed down for generations and are the result of open pollination rather than grafting, cutting or genetic manipulations — is important for Solorio.

“Most of these seeds you can’t find at a Home Depot,” said Solorio, who’s involved in an international online seed exchange. “These are so unique — to me, these belong to the people.”

He said he doesn’t sell the seeds, but instead gives them away.

“I share the seeds,” he said. “I can’t sell something that’s not mine.”

Organizers hope the nonprofit event, which helps fund the educational efforts of the School Garden Network of Sonoma County, is a learning experience for attendees of all ages. New this year are small, in-depth roundtable discussions, labyrinths made from produce and an heirloom tomato tasting, organizers said.

“It’s about knowledge,” said Lisa O’Leary, who works for Baker Creek Heirloom Seed Co., which organizes the event. “You can grow things from seeds and save those seeds and grow them again next year. You’re not dependent on the grocery stores.”

Amy Lint, 41, who brought her three home-schooled children from San Diego to the expo for the first time Tuesday, said the event was an opportunity for a hands-on lesson in agriculture.

“I felt like they were a good age to plant the seeds, really literally of the importance of growing our food and thinking about it,” Lint said. “Also there’s the celebration piece of it. It’s fall and its the beginning of the harvesting aspect.”

Sophie Conner traveled from St. Louis, Missouri, to see the expo. It was her first time.

“I’ve never seen anything like this in my life,” said the 83-year-old home gardener, who was looking for Moringa seeds.

For more information, visit theheirloomexpo.com.