So many exciting new perennial plant varieties appear every year, offering more colors, better hardiness and disease-resistance, and other enticing features. It's easy to get drawn in by the marketing hype, but how can you know if these varieties will actually deliver on all those promises? To see how these plants actually do in practice, the Colorado State University’s Flower Trial Garden puts them to the test over a two-year period, and each year, it picks out a few outstanding varieties. It recently named six perennials as its 2019 top-performers, and you can bet that if these plants can stand up to Colorado's high altitude, large temperature swings, and even punishing hailstorms with minimal care, they truly are tough beauties worth adding to your garden.
John Stireman/Courtesy of Plant Select
1. Granita Orange Ice Plant
When in bloom, this power perennial might remind you of California's famous super bloom because it creates a bright orange carpet of long-lasting flowers. One of the best at blanketing the landscape with blooms, Granita Orange ice plant only grows about two inches tall, but can spread several feet. Hardy in Zones 5-8, it prefers full sun and can tolerate dry soil as it blooms profusely from spring until fall. Despite its fragile appearance, judges noted that it held up well year over year, even in frigid Colorado winters.
Courtesy of Walters Gardens, Inc
2. Summerific 'Cherry Choco Latte' Hibiscus
This hibiscus hybrid may look tropical but it is hardy in Zones 4-9. 'Cherry Choco Latte' is named for its large, deep pink and white blooms that appear from mid summer into fall, and the chocolate-brown tinge its new leaves feature. This shrubby perennial can grow up to four feet tall and will do best in full sun to part shade. In the CSU trial, it earned praise for not needing to have old flowers deadheaded (they naturally fall off when they've shriveled) and because its "mid-size height made a good balance with the flower size."
Courtesy of Dummen Orange
3. Dianthus Kahori 'Scarlet'
In spring, this perennial produces a profusion of bright magenta flowers with white centers, but Dianthus Kahori ‘Scarlet’ also impressed trial judges with its though grass-like foliage. They noted that this variety showed remarkable hardiness for a dianthus, never dying out in the center over the winter as is common with this species. Hardy in Zones 3-9, Dianthus Kahori 'Scarlet' prefers things on the dry side with plenty of sun, so it works well in a rock garden or container. It’ll only grow about six to eight inches tall, so it also makes an attractive ground cover or edging plant for a walkway
Courtesy of Danziger
4. LAMI Dark Purple Spotted Deadnettle
When you need a beautiful groundcover for a shady spot, LAMI Dark Purple (Lamium maculatum) will provide attractive green foliage and rich purple flowers in gardens in Zones 4-9. It only grows about six to eight inches tall, but it can spread up to nearly two feet in both partial and full shade. It usually blooms from late spring through early fall, and it makes a stunning choice for containers and hanging baskets, too. In particular, trial judges praised it for not burning in the sun while still holding up well in the shade, and blooming from spring to fall.
5. Millenium Ornamental Onion
Trial judges couldn't get over what they called an "insane amount of flowers" on this ornamental onion variety, and the fact that the blooms didn't flop over when watered from above (which can sometimes happen with other varieties of this plant with a sprinkler or rainstorm). Hardy in Zones 4-8, this tough perennial's pinkish purple blooms can last all summer, attracting plenty of bees and butterflies. Millenium ornamental onion does best in full sun or part shade, where its stems usually grow between 15 and 20 inches tall.
Courtesy of Emerald Coast Growers
6. Bandwidth Maiden Grass
While maiden grass (Miscanthus sp.) has a reputation for being invasive, 'Bandwidth' is a sterile variety that won't reseed itself everywhere. In fact, in the trial, it didn't even bloom once, but it still impressed judges with its beautiful yellow and green striped foliage. Plus 'Bandwidth' stays more compact than the species, topping out around three feet, so it's a smart choice for small gardens. Hardy in Zones 5-9, it will thrive in full sun to part shade.