Helleborus for Colorado

Posted by Jim Klett – CSU Professor and Extension Landscape Horticulturist

In our 2 winter, 3 growing season perennial trials at Colorado State University we have been trialing numerous species of Helleborus for five years.  I have been extremely impressed with their performance and hardiness and adaptability in our trials.  The common name is lenten rose and they generally grow 15-18 inches in size and 15-20 inches or more in width.  Plants are evergreen but sometimes the foliage can get battered by late winter.  If this happens, prune off the dead leaves at this time to make room for new growth and flowering.  Some gardeners mow the old foliage off of large plantings of the lenten rose for complete renewal.

The flowers start blooming in mid to late February with rose or cream speckled flowers and bloom for a long time.  The sepals are attractive for a long time after blooming.  Helleborus can reseed heavily by the hundreds under certain conditions.  Usually the seedlings are located at the base of parent plant and can flower in about the third spring.  This can create a nice effect in a natural setting.

Helleborus generally prefer a more moist organic well-draining alkaline soil.  We have them planted in partial to full shade and they have performed excellent.  They will tolerate some drier conditions in the summer.  Plants are long lived and once established, division is seldom.

We have planted many varieties of the Gold Collection® series from Skagit Gardens.  Two that appear outstanding include:  Maestro Hellebore (Helleborus x  ballardiae ‘COSEH890’).  Plant has shiny dark green foliage appearing almost black at times toward the end of the season.  Flower petals emerge a deep pink with white and mature to a creamy white with shades of dusty rose on the backside.  Flowers covered the plant from side to side and was very prolific.  Plants were compact and with good vigor.

Maestro Hellebore in mid-March

Maestro Hellebore in mid-March

Flower fades to a dusty rose color in mid-April 

Merlin Hellebore (Helleborus x ballardiae ‘COSEH810^{USPP #22350}) flowers on this Hellebore emerged with pink color that is brighter than most and then matured to shades of dusty rose.  Blooms were held above foliage creating an impressive display.  Plants were more compact with long lasting dark green foliage and very low maintenance.

Merlin Hellebore with a deep pink color in mid-March

Merlin Hellebore flower color matures to a dusty rose in mid-April

Merlin Hellebore with dense, compact growth habit in mid-April

Hellebores are a great perennial for late winter early spring flower color that are evergreen and low maintenance.  If you do not have some in your garden try some and enjoy the early spring flower color and nice green foliage throughout the rest of the year.

Perennial ‘Top Performers’: Information from the CSU Two-Year Perennial Trial

By: Jim Klett, Professor and Extension Landscape Horticulturist, Department of Horticulture and L.A., Colorado State University

Now since it is officially spring, industry professionals and gardeners are thinking of growing and planting perennials. I hope you will consider these ‘Top Performers’ from the CSU Trials. These perennials were planted in 2010 and researched for 3 growing seasons and 2 winter periods.  For more information on the perennial trials, visit our website. 



Buzz™ Butterfly Bush

Buddleia davidii ‘buzz™’ ^PPAF series, (Buzz™ Butterfly Bush Series) – This entire series was noted for excellent flower production and dense growth. Range of colors in series was Blue Violet, Ivory, Pink Purple, Violet and Magenta. These more compact Butterfly Bushes work well as a mixed border plant.

Gold Collection® Lenten Rose

Helleborus x ballardiae ‘Gold Collection®’ series, (Gold Collection® Lenten Rose series) – The plants were noted for early blooms (March) with flowers facing upright and dark glossy green foliage year round. These plants make a great groundcover for a shady area. Flower color varies from a pink blush with yellow interior to pink blush on chartreuse petals.



Fireball Bee Balm

Monarda ‘Fireball’ ^{PP #14,235}, (Fireball Bee Balm) – Plants are prolific bloomers in July with wine colored blooms on sturdy stems with no lodging, even with overhead irrigation. They have superior mildew resistance and great for the back of perennial border.

Phlox paniculata ‘Classic Cassis’ ^PPAF, (Classic Cassis Perennial Phlox) – Plant has a long bloom time with big bold flowers. Flowers are a bright pink color with hints of mauve which start in June and continue well into August. Plants have good clean green foliage throughout the season.



Pina Colada Perennial Phlox

Phlox paniculata ‘Pina Colada’ ^PP#19968, (Pina Colada Perennial Phlox) – Pure white flowers are impressive against the dark green foliage from June into September. Growth habit is compact and spent flowers drop off the flower panicles that give plant a clean look throughout the season.

These five perennials are a must for producers, retailers and gardeners for the 2013 growing season.