Tribune News Service | Enlarge – The giraffe sculpture in the garden of Duane Miller and Mary Ann O’Brien on August 4, 2016, in Stillwater, Minn.

STILLERWATER, Minn. – Mary Ann O’Brien will do everything it takes in the fall to ensure she has glorious dahlias, the Dom Perignon of her gardens, in the spring.

On a chilly November day after the first frost, O’Brien was on her knees digging tubers from more than 25 different dahlia cultivars to store for the winter. After they dry out in the garage for a few days, she slices and divides each tuber, multiplying the number she’ll have to plant in spring.

“I make sure to get a piece of stem with each one,” she said. Then O’Brien rolls the dozens of tubers in plastic wrap, stands them vertically in cardboard boxes with ends open, and sprinkles the tubers with vermiculite. Lastly, she records the color or variety name on index cards and stores them in a big cooler at 40 to 50 degrees.

It’s tedious, hard work, she admitted. “But by August, the blooms are so showy you can’t take your eyes off of them. Dahlias never disappoint.”

The showstopping dinner-plate-sized ‘Zorro’ and ‘Weston Spanish Dancer’ are only a small part of O’Brien’s sprawling gardenscapes, which she designed, planted and tends with her husband, Duane Miller, on their Stillwater property, where they’ve lived for more than 20 years.

The couple built their walkout rambler in 1993 on a 1-acre lot abutting the Indian Hills Golf Course. Even before the builder broke ground, the longtime passionate growers were plotting where they would dig their gardens for the best sun exposure. Fortunately, excavation for the walkout created two big berms, resulting in visually interesting rolling terrain for the garden beds.

The couple amended the hard clay soil with truckloads of black dirt and launched what would become a two-decade labor of love.

O’Brien and Miller consider their gardens “evolutionary” because the landscape was shaped over time with flower beds, bushes and trees, as well as countless boulders from a quarry in Wisconsin.

“The fun part was selecting the plants and the trial-and-error of successfully growing them,” said O’Brien.

Today the thoughtfully planned O’Brien/Miller creation boasts season-long blooms _ from daffodils and tulips in…