Seussian spires on display
5-foot-tall dazzlers burst with tiny pink flowers that age to lavender
Over the past 18 months, horticulturists at Denver Botanic Gardens went to great lengths to sow tiny seeds and nurture them into spectacular flowering plants now standing about 5-feet tall — and growing. The botanical name Echium wildpretii doesn’t do the plants as much justice as the common name: Tower of Jewels.
“It’s one of my favorite plants,” horticulturist Nicholas Giaquinto said of echium (pronounced EK-eeum). “We wanted another amazing plant of interest during early spring when most things are still starting to emerge — something that would wow people.”
Exotically beautiful and impressively tall, echium are the supermodels of the gardens’ April display. Now gracing the orangerie, the containerized echium will live outdoors once nighttime temperatures warm to above 28 degrees.
Echium spout a fountain of silvery foliage. Large spikes fringed with leaves in a twisting pattern bear tiny, delicate flowers that change color as they bloom. With a form that could have flowed from the imagination of Dr. Seuss, echium originate on tiny Tenerife, a sunny Canary Island off the coast of Morocco. In the wild, plants grow up to 8-feet tall in the sub-alpine zone at elevations of 4,200 to 6,500 feet above sea level.
Echium self-seed like weeds around San Francisco; yet given our colder winters, cultivating the biennials in the Mile High City is no walk in the park. Denver’s echium adventure began several years ago when Denver Botanic Gardens horticulturist Bridget Blomquist saw the magnificent plants online and wanted to grow them.
Propagation horticulturist Katy Wieczorek realized the difficulty of cultivating these plants in Denver, yet accepted the challenge. A cadre of horticulturists devotedly cared for the echium as seeds germinated and plants flourished.
Echium prefer well drained soil, so the potting mix includes orchid bark, large perlite and charcoal. “It dries out faster, so we can water more often,” Giaquinto said.
To grow a plant large enough to produce a flower spike, horticulturists fertilized the echium with each watering. They constantly adjusted the soil’s pH. They monitored roots weekly to determine when to repot. They transplanted the echium six times, eventually to 7-gallon containers.
To flower, echium require a cooling period of at least six weeks. In November, the echium were relocated from the York Street location in Denver to the suburban Chatfield Farms. There, Andrew Habig oversaw the echium in the cooler environment until the plants were moved back to Denver in March. The plants took up residence in greenhouse hallways because they’re too big for the greenhouses.
“Our biggest concern is room,” said Giaquinto. “They take up so much space.”
After about a month, the echium began to flower. The ‘Towel of Jewels’ blooms first open up pink, but they fade to purple, so it’s showy in all stages of its life, Giaquinto said. “The flower spikes last three to four week.”
Echium pininana – commonly known as ‘Tree echium’ or ‘Snow Tower,’ produces white flowers.
“Bees love them,” Giaquinto said. “Echium have so many flowers, so there’s a big pollen yield.”
DBG horticulturists plan to transplant a few echium to garden beds and monitor their performance in the landscape.
“It’s a large effort for us, and we’re glad we’re able to grow them,” Giaquinto said. “They’re worth the work because they’re such a beautiful plant. And we wanted to prove we could grow echium in Denver.”