While some gardeners are taking guidance from the Slow Flowers movement, Colorado State University has long studied which plants work best in the Rocky Mountains at its Flower Trial Garden, and researchers there recently revealed their top perennial picks for the area. The plants submitted for the trial were all introduced in the last few years; entries are grown in the CSU gardens for three summers and two winters before the winners are announced.
Here are the top performers for the 2019 CSU Perennial Trial, with the growers that submitted them and the judges' comments:
Millenium Ornamental Onion
Eason Horticulture Resources and Stonehouse Nursery
(Allium hybrid ‘ALLMIG1’)
This was a definite “show stopper” plant that was described as having an “insane” amount of blooms. Flowers were a nice shade of pink and were a favorite of many bees and butterflies. The flowers combined well with a nice compact plant with clean foliage and very uniform growth habit. Blooming lasted a long time and flowers did not lodge even with overhead irrigation. It has been reported to grow well even at 8,000’ in the mountains. Removal of spent blooms can result in some repeat blooming or can be left for winter interest. Judges were in unanimous agreement to designate it as a winner. (See photo above.)
(Dianthus x hybrida Kahorie® ‘Scarlet’)
Very showy in the spring, with a very vibrant color and attractive plants. Flower color was not a true scarlet but a beautiful shade of hot rose or cherry. Plants had superior winter hardiness that was consistent over three years and did not die out in the center, as did many other Dianthus. Plants were attractive even when not in bloom, with a nice tidy, compact growth habit.
Walters Gardens Inc.
(Hibiscus x hybrida ‘Cherry Choco Latte’PPAF)
Large, two-tone blooms were captivating with a striking combination of pink and white. It makes a great choice for providing color late in the season. Plants were relatively low maintenance as the old blooms were self-cleaning. Foliage had shades of dark red that was maintained throughout the season. Plants also had a nice growth habit that did not lodge, and the mid-size height made a good balance with the flower size.
(Lamium maculatum ‘Dark Purple’)
Dark purple flowers combined with dark green foliage and a very uniform growth habit to make a very impressive ground cover. This versatile plant did not burn in the sun and did well in the shade. It has also been reported to look great even at 8,000 feet elevation. Plants have superior vigor and provide a long period of bloom.
(Miscanthus sinensis ‘NCMS2B’PP29460)
This is a good selection for today’s smaller gardens and landscapes, as the plant maintains a nice uniform growth habit that is only 3-4’ in height. Plants did not bloom but the foliage is very attractive, with yellow stripes running across the blade. The variegated foliage did not revert and was impressive all three seasons. Flowers are not needed for interest as the yellow and green contrast in the leaves is very showy.
Bright, iridescent orange flowers blanket the plant, creating an impressive show of flower power. Large flowers bloom over a long period. Plants make a very attractive ground cover as the beautiful green foliage forms a nice dense mat that tightly hugs the ground. Vigor is excellent and makes a good spreader. Cold hardy and well suited for this area.
For now, CSU’s Flower Trial Garden is closed to the public because of COVID-19 concerns; it generally draws thousands of visitors each year. But while you can't see the garden today, CSU workers are definitely busy on the next round of tests, learning which plants grow best in this climate. Find updates here.