Front Range gardeners know our homeland holds particular landscaping challenges: We never plant before Mother’s Day, and we frantically put twinkly lights on our fruit trees during those inevitable spring snowstorms. We need perennials that can withstand summer’s intense sunshine and our unpredictable winters.
Thankfully, Colorado State University’s team of horticulturists has our weeding-weary backs with its 10-year-old, open-to-the-public perennial trial garden—a literal testing ground to see which new varieties thrive in our finicky climate. (CSU has also been evaluating annual flowers for 30 years.) “There are so many perennial plants coming from breeders,” says Jim Klett, a professor and extension landscape horticulturist at CSU who oversees the research. “We want to understand what’s going to grow best here in Colorado.”
To that end, CSU receives samples of cultivars that’ve been introduced in the past few years from commercial breeders. (The plant companies pay a fee for trial inclusion that covers the cost of growing and helps fund a graduate student who manages the research.) Seeds are planted in the spring near the arts complex, and they receive basic watering and fertilization. CSU tracks plant growth with biweekly measurements and photos.
Ultimately, the trial observers look for plants that provide visual interest throughout the year, rather than one short-lived burst of color, Klett says. The plants need to make it through two winters (they’re judged in November, so they see three full summers) with only minimal care and must also prove disease- and insect-resistant. CSU then releases its new class of top performers each April—just in time for the start of Colorado’s planting season.
To try out the winners at home, ask for them at your local, independent nursery; CSU works with the Garden Centers of Colorado, which has shared the recommendations with its members. “These might be tougher to find at the big-box stores, but most of the independent garden centers tell me they’ll be ready with these plants,” Klett says. Here’s the complete list of top-performing new perennials.
- Windwalker Big Bluestem from Plant Select (Andropogon geradii ‘P003S’)
This ornamental grass delivers soft-blue foliage that transitions to a deep maroon in the fall and winter months. The plant will grow to about six feet tall and can thrive with little supplemental watering.
- Alexander’s Great Brunnera from Terra Nova Nurseries (Brunnera macrophylla ‘Alexanders Great’ PP25, 789)
Another large plant, this Brunnera works well in shady areas but also produces a healthy display of blue flowers. The substantial ground cover can grow to knee height.
- Heuchera Carnival Rose Granita from Darwin Perennials (Heuchera x hybrid ‘Carnival Rose Granita’ PPAF)
This plant’s foliage offers a range of pink, purple, and green hues combined with a silver overlay that almost glows in the sunlight. The CSU team suggests using this good-for-shade variety in mass plantings for a stunning effect.
- Forever Purple Coral Bells from Terra Nova Nurseries (Heuchera ‘Forever Purple’ PPAF)
The leaves of this shade plant produce a deep, vibrant purple that informs its name. The glossy leaves and vivid flowers keep their colors for most of the season without fading.
- Summerific Cherry Cheesecake Rose Mallow from Walter Gardens/Proven Winners (Hibiscus x ‘Summerific Cherry Cheesecake’)
Klett notes that this plant is particularly stunning when placed in a very sunny area. The flowers are saucer-size and almost feel tropical but require some patience, as those impressive blooms won’t appear until late July.
- Crazy Blue Russian Sage from Darwin Perennials (Perovskia atriplicifolia ‘CrazyBlue’ USPP25639)
This Russian sage thrives in dry locations and produces many blue flowers. The plants will appear dense and offer an exceptionally long bloom period.
- Glamour Girl Garden Phlox from Walter Garden/Proven Winners (Phlox paniculata ‘Glamour Girl’)
CSU describes this plant as “one of the best garden phlox introduced in a very long time.” Upright and uniform, Glamour Girl offers gorgeous salmon-color flowers. Klett adds that these phlox appear to be fairly mildew-resistant compared to other phlox in the trial.
- Bonus “Too Good To Wait” Pick: Kahori Border Pink from Bartels (Dianthus ‘Kahori’)
Although this boom spent only one winter in the trial, Klett says its performance is so outstanding the team opted to highlight it with this year’s group. The compact plant offers long-blooming pink flowers with a tolerance for heat. The uniformity of these blooms would work well in ground beds, in a border, or even in containers.