As visitors stream out of the Sonoma County Fair’s floral wonderland filled with the oxygen jolt from so many respirating plants, they run into a Hall of Flowers in miniature — fanciful gardens created by amateurs.

Like the pros beyond the big door, the Junior Exhibitors, aged 9 to 19, toil for hours over many months to conjure up what appears like a mature garden complete with working water features, trees and props, all coming together almost overnight.

TV’s “Yard Crashers,” with all their expert behind-the-scenes support, have nothing on these kids, who do most of the work on their own, from procuring plants to caring for them to designing their spaces, installing everything and then making sure their garden looks fresh over the two-plus weeks of the fair.

There are 16 different 8-by-10-foot youth plots filled with floral eye candy and claimed by individuals, teams of pals or FFA and 4-H clubs. And while only one will win Best of Show, the Danish judging system that makes it possible for everyone to get either a blue or red ribbon creates a spirit of collaboration within the courtyard that is as valuable a life lesson as the gardening skills they gain in the process.

“I’ve made a lot of friends just being there and planting the garden. Everyone helps each other,” said Bella Hayes, who at 16 has been a junior garden exhibitor half her life.

Creating show gardens is a Hayes family affair. Sister Lily, 12, is teaming with a friend on her first solo garden this year and brother Demetri, 13, is helping with the group garden of the Steuben 4-H Club of Santa Rosa, where Bella is the junior advisor. Mom Melinda is chauffeur and plant go-fer, but by the rules she must keep her hands out of their garden.

“I get my hand slapped all the time,” she confessed, “because I want to help.”

Their mentor for advice and hands-on support is Dayna Justus, longtime Steuben 4-H garden project leader who also, with her own mom Arley Nelson, creates an amateur adult garden. They’ve won every award possible over the last 15 years.

The process begins in early spring when kids begin assembling at Justus’ Santa Rosa home, where she maintains a nursery of plants in pots. She grows everything from begonias and hydrangeas to redwoods, all of which get re-used in show gardens year after year. She also stores props, stones and other materials that make up the hardscape and water features.

“It’s fun to learn more about plants and to have people that can help you. We’re learning how to care for the plants, how to give them a better chance of staying alive,” said Jaylee Edwards, 11, who at a recent work party before the fair was busy pulling dead plants from 6-inch pots in order to save the still-good potting soil in a large bucket.

Thrift like this is essential when it comes to participating in the fair. It could easily cost hundreds of dollars to buy the plants, soil, materials and props to create a winning garden. Hundreds of plants are needed to create that densely packed look; no soil can be exposed or they’ll lose points. Exhibitors also must have plenty of spare plants on hand to replace any wilted blooms, not just before judging but throughout the long run of the fair.

Local nurseries and garden centers help with donations. Bella Hayes said Home Depot has been her great friend. She and the Steuben 4-H Club have also received a lot of generous donations from Blooms, a wholesale nursery in Glen Ellen.

Blue Ribbon winners get $475, and $450 for red. There are also $25 bonuses for best background and maintenance. There’s a new award this year, $250 for Best Use of Yellow put up by Sonoma Ag Art, a company established by the late Saralee Kunde, a lifetime friend of the fair. Yellow was her favorite color.

Prizes rarely cover the cost, however, prompting Justus to keep her own home nursery.

During work parties kids learn to deadhead, snip yellow leaves so plants appear perfect, and learn horticultural basics like how much water and light each plant needs to thrive.

Bella Hayes, who picked the theme “Don’t Worry, Be Hippie” as part of the Hall’s groovy 1960s “Flower Power” theme, said she’s learned over years of practice not to over-plan and to be flexible. One year the family took over the driveway, laying out an entire garden with masking tape and loading each plant in the trailer in that order. But once they started putting in the soil and hardscape at the fairgrounds, those careful plans were tossed.

“Once you start putting it in,” mom Melinda said, “these gardens take on a life of their own.”

You can reach Staff Writer Meg McConahey at meg.mcconahey@pressdemocrat.com or 521-5204.