CO-Horts Blog

Monday, January 17, 2022




By CSU Horticulture Agent, Linda Langelo

                                        Photo credit: Fossil Creek Tree Farm, Cheyenne Spirit

New research is being done all the time with cultivated varieties. One such garden that does trials on coneflowers and many other perennials is Mt Cuba Center. This garden is a botanical garden that studies native plants and plant conservation.

Coneflowers are native to central and eastern United States. Coneflower or Echinacea is a clump-forming herbaceous perennial. Echinacea purpurea produces roots that are more fibrous while other species produce roots that are taproots. This allows them to grow in areas that experience drought and in areas that have heavy competition from other plant's roots. All coneflowers require well-drained soils. The fibrous root system of Echinacea purpurea makes it an ideal plant for many garden sites that have a perennial mix.

Some of the nine species Mt Cuba Center studied grow here in Colorado. The observation of these plants was over a two-year period. Both the performance and visitation of various pollinators was recorded. No fungicides were used during the two-year period. Supplemental water was provided in the first season only to allow the plant's roots to become established.

Of all the Echinacea purpurea species trialed at Mt Cuba Center, the cultivated varieties that performed the best were Echinacea purpurea 'Pica Bella' and Echinacea purpurea 'Fragrant Angel'. Why were they chosen? Their overall habits were sturdy, semi-compact that resisted flopping. There was no need of staking.

Echinacea purpurea 'Pica Bella' is a cultivated variety that most resembles the straight species, Echinacea purpurea in its floral display. This variety also ranked ver high in the number and types of pollinators that were found on the prominent orange cones during the late June to mid-July bloom time. Among the types of pollinators were butterflies, bees, and wasps. The plant will reach a height of only two feet compared to the four feet of straight species. 

                                     Photo credit: Missouri Botanic Garden - Pica Bella

Echinacea purpurea 'Fragrant Angel' is the highest rated of all the cultivated varieties of a white flowering Echinacea. The blossoms are around four and a half inches wide that flower from July into August. This plant is also ranked very high for attracting pollinators such as bees, wasps, and butterflies.

                                            Photo credit: White Flower Farm - Fragrant Angel

Overall, Echinacea are short-lived plants unless they are started from seed. They also have an incurable systemic disease called Aster yellows. It is a pathogen called a phytoplasma, a microorganism that is spread from plant to plant by leafhopper insects. The only way to reduce the spread of the disease is to get rid of the infected plants. 

The other issue with Echinacea is eriophyid mites which can cause unusal growth in the floral cones. In this case the removal of the floral cone can help to control the mites. The symptoms for eriophyid mites are localized infection with the lack of green leafy growth originating from the flowers.

In Sedgwick County Extension, we started a trial garden of Echinacea in 2021. We will see which ones overwintered and how prolific and disease free they are in 2022. The cultivated varieties we chose were based on local availability in the nurseries. These were the following Echinacea

  • 'Cheyenne Spirit (Echinacea hybrida)
  • 'Prairie Giant'
  • 'Kim's Knee High'
  • 'Solar Flare'
Photo credit: Missouri Botanic Garden - Prairie Giant

We wished we could have purchased Echinacea 'TNECHKR' and Echinacea paradoxa. According to Mt Cuba Center they were very prolific with flowers and had the greatest garden adaptablility. Echinacea paradoxa, a yellow flowering coneflower also produced vigorous, disease-free plants. Who doesn't want that for their gardens.

                                 Photo credit:


Photo credit: reddit - Solar Flare

Monday, January 10, 2022

“Top Performer” Perennials” from the 2021 Colorado State University Flower Trials

Posted by: Dr. Jim Klett, Department of Horticulture and Landscape Architecture, Colorado State University

 In 2021, Colorado State University continued its three year herbaceous perennial trial and chose eight perennials as the “Top Performers” from 126 that were planted in 2019. To become a CSU ‘Top Performer’ it has to have great survival percentages after two winters and three growing seasons and scored excellent throughout the three growing seasons. A sub-committee if the CSU Annual Trial Garden Advisory Committee evaluated twelve of the top performing perennials in November of 2021 by examining photos of these plants taken every two weeks during the three year growing seasons. A majority favorable vote from the committee is needed for a perennial to become a CSU ‘Top Performer’.

 Therefore perennials that get this description have proven to be adaptable for the Front Range of Colorado. The following eight plants have been awarded this category for 2021 after three years of extensive trialing.

 A complete report on the perennials in the trial can be viewed at under the Perennial Trials menu tab.

Achillea ‘Firefly Sunshine’

(Achillea x hybrida) from Walters Gardens, Inc. /Proven Winners®

Vibrant yellow flowers provided a lot of color and with a long-lasting bloom. Dark green foliage also made the flower color stand out. It had superior qualities with a more compact growth habit that did not lodge despite overhead watering and had excellent winter survival. It was also noted that it did not spread around the garden which is a definite plus.


Brunnera ALCHEMY™ Silver

(Brunnera macrophylla) from Terra Nova Nurseries

This great plant can brighten up a shady area with a constant display of beautiful silver foliage. Plants are vigorous and are covered by a delicate cloud of light blue flowers from about May into June. Leaves are relatively thick and stands up well with strong stems to create a very attractive and uniform growth habit. 

Eupatorium Euphoria™ Ruby

(Eupatorium purpureum 'FLOREUPRE1’PP31,668) from Darwin Perennials®

Shorter and more compact than the species, this is a nice medium size plant for the modern landscape. This was a unanimous choice for the “Top Performer” award with dependable light ruby/lilac-colored flowers that combines well with dark leaves and stems. It was noted to be an excellent pollinator plant.


Perovskia CrazyBlue

(Perovskia atriplicifolia 'CrazyBlue' PP #25,639) from Darwin Perennials®

Plants were noted to have superior flowering and growth habit. The flowers have a long lasting bloom period and the violet-blue flowers last longer than other Perovskia. Uniform plants had interlacing branching and sturdy stems that kept it from lodging and maintained an attractive appearance all season. It is a mid-sized plant about 3-4 feet in height.


Rosa Sunbeam Veranda®

(Rosa x ‘ Korfloci52’ PP23,314) from Star® Roses and Plants

Glossy, dark green foliage made the bright yellow flower color even more stunning. Blooming started in June and lasted well into September. The compact size makes this a great choice for smaller gardens spaces. Plants had excellent winter hardiness.


Rosa Cherry Frost™

(Rosa x ‘Overedclimb’PP31,286) from Star® Roses and Plants

 Abundant bright red flowers and good disease resistance make this a good climbing rose for Colorado. Clusters of small flowers kept repeating throughout the growing season in flushes for long lasting color. It had excellent winter survival.

Sedum Prima Angelina

(Sedum rupestre) from Darwin Perennials®

Great neon yellow foliage makes this an excellent foliage plant in the summer and it also is quite showy in the winter with a nice shade of red. The spreading growth habit is very uniform and a great choice with rock gardens or combined with other Sedums for additional color contrast. Prima Angelina is superior to the straight Angelina with better branching and growth habit while also being less brittle.

Veronica Moody Blues® Mauve Improved

(Veronica spicata) from Darwin Perennials®

Impressive vibrant, mauve colored blooms covered the plants at peak and repeated later in the season. Well branched plants were compact and very uniform with 100% winter survival. It has the added bonus of being a good bloomer the first year in the garden.


Tuesday, January 4, 2022

Evergreen Trees for Dry Sites

by Amy Lentz, CSU Extension Horticulture Agent- Weld County

Even with recent snowfalls, many of us are still in some sort of drought in Colorado. It’s been unseasonably dry over the past fall and winter so far and our trees could suffer if they don't get moisture during these dry winter months. We've talked before about the importance of winter watering, but I also wanted to take a moment to cover just a few evergreen trees that can better withstand drier conditions, whether you create those conditions through xeriscaping or you just want to choose the right evergreen tree for your dry location.

Pinyon pine (Pinus edulis)

Pinyon pine tree. Photo by Colorado Springs Utilities Xeriscaping.

This is a great option for those living along the Front Range and lower elevations and if you are dealing with a steep slope where water runs off frequently. However, they don’t like to be wet, so placing a Pinyon pine in the middle of your lawn where it gets watered three times a week is not ideal and the tree will likely suffer. It’s a smaller evergreen tree with two needles per bundle and attractive smaller cones. These cones are where we get pine nuts!

Pinyon pine cones. Photo by Colorado State Forest Service - Colorado State University.


Bristlecone pine (Pinus aristata)


Bristlecone pine tree. Photo by Oregon State University.

Bristlecone pine is a unique tree with a smaller mature height of around 20 feet tall with short, dark green needles that have tiny white resin dots on them (and often mistaken for bugs). Once you see past the dots, you will notice that this tree has a nice form and holds its needles for several years. This tree also grows very slowly, so you can even use it on your front porch in large containers until you are ready to plant it in the ground.

Bristlecone pine needles. Photo by Oregon State University.


Rocky Mountain juniper (Juniperus scopulorum)


Rocky Mountain Juniper Trees. Photos by Oregon State University.

This is one tough tree! Rocky Mountain junipers are often utilized in the worst conditions, like a windbreak on the Northern plains where the wind never stops. They are pyramidal in shape and small in mature height, reaching around 15 feet, depending on what type you choose. The overall color of these trees can range from green to blue, again depending on the cultivar. Look to your local nurseries to find specific cultivars such as 'Wichita Blue', 'Woodward' or 'Cologreen'.

The list of good evergreen trees for dry sites doesn’t stop with this blog, there are plenty from which you can choose. For a more complete list of all evergreen trees for Colorado landscapes (including those or more moist sites), check out our CSU Fact Sheet #7.403 - Evergreen Trees.