In spring, buds form a whorl at the crown, and a succession of satiny yellow flowers unfurl for months.

“Golden barrels are more popular than ever,” says Molly Thongthiraj, co-owner of California Cactus Center in Pasadena.

Five years ago, the store provided the Getty Center with 552 of the spiny tuffets for the South Promontory garden. The plants — 15 to 19 inches in diameter when installed — are now 20 to 24 inches, Thongthiraj says.

The inch-per-year growth rate slows as golden barrels approach maturity at about 36 inches in diameter.

Golden barrels tolerate more irrigation than other cactuses and consequently do not rot as easily. According to Thongthiraj, the plants do equally well in desert gardens and in landscapes that require slightly more water.

“They’re the perfect finishing touch for a succulent garden,” she says.

The Sullivans’ previous residence mixed spherical and columnar cactuses with aloes, agaves, kalanchoes and other succulents — plants that store water in fleshy leaves and stems in order to survive drought.

The couple’s new home has a front garden that’s smaller, so they disciplined themselves.

“With succulents, it’s tempting to want one of everything,” Margaret says.

They went with a limited palette of barrel cactuses and other sculptural, architectural plants that suited the contemporary lines of their remodeled home. Against a backdrop of greenish tan walls, columnar cactuses mix with Yucca rostrata trees with strappy leaves.

Chris planted one yucca so its trunk was parallel to the ground. The tree has since curved upward, lending a sculptural element that contrasts effectively with the angular hardscape and the setting’s strong vertical lines.

Enhancing the composition are boulders from the couple’s previous garden. Other transplants include low-water Mexican blue fan palms (Brahea armata) and Napoleon’s hat (Kalanchoe beharensis), diminutive succulent trees with boat-shaped, feltlike leaves.

Through it all, clusters of golden barrel cactuses pop up like spiny beach balls.

The Sullivans made a point not to place plants equidistant from each other.

“We gave some thought to how they might look in nature,” Margaret says. “Randomly spaced, odd-numbered groupings seemed to work best.”

Because the soil was compacted — “like concrete,” Chris says — they hired a crew to haul a significant amount to the dump.

“We brought in 10 yards of decomposed granite for the substrate,” he says. “On top of that went a blend of DG and cactus mix. Our main goal was good drainage. These plants need loose soil that drains well.”

The top dressing is 3/8-inch golden gravel. The installation probably cost more than a typical frontyard landscape, Chris says, declining to provide specifics, “but it’s 100 times less work than a lawn.”

The new garden gets no pesticides or fertilizer, and rabbits---which eat ornamental plants in neighbors' gardens---leave the Sullivans' alone. Chris keeps a safe distance, too, and uses long-handled tweezers to extract weeds growing close to the cactuses.

Thongthiraj says her father---who founded the specialty nursery 35 years ago---likely would have appreciated the Sullivan garden.

"He had a passion for golden barrels and taught us kids how to collect and germinate the seeds. We used to hate having to do it. His goal was to have a million of them.”

The nursery may not have a million of them, but propagating golden barrels has proved worthwhile.

“Surprisingly, they’re hugely popular in China,” Thongthiraj says. “We ship them there all the time — whole containersful.”