CNGA Looseleaf Dec 2018 Jan 2019

20 colorad o nga.org LooseLeaf December 2018/January 2019 We have been trialing many different Dianthus species over several three-year perennial trials. The plants are tested for two winters and three growing seasons, which gives a good indication if a variety is truly a perennial suited for Colorado. Many Dianthus are tricky to grow, requiring closely monitored water, well aerated soil, and prevention from crown rot. In our trials, we do not have winter irrigation, and soil is a clay with some amendments. This can be a problem for some Dianthus that need well-drained crowns. The Dianthus varieties that have shown less winter hardiness have typically been the broadleaf, carnation type. These varieties generally grow about 8 inches tall and 12 inches wide, and seem to be more floriferous in cooler weather. They are showy and available in a wide range of colors, but do not seem to withstand cold well. Often they do survive the winter, but die all the way back to the ground and reappear in the spring with very low vigor. We have found their survival rate to be quite variable depending on the severity of winters, and can be as low as 50 percent and as high as 90 percent. Due to our experiences with the lower dependability of many of these carnation-type Dianthus, they may be more suited to be planted as an annual in Colorado. Some varieties we have tested that required more protection and care include the ‘Sun Flor’, ‘Odessa’, and ‘Flow’ series. Meanwhile, many of the carpet-like and spreading Dianthus varieties seem to survive our colder winters better. Flower color on these varieties is often more limited to pinks, reds, and whites, but many can be outstanding. They generally grow to about 4 inches in height and spread and fill in an area quickly. The foliage is often more needle-like and color ranges from silvery-blue to emerald green. Many are evergreen in nature, which gives them year-round interest. Blooms can begin as early as April and can extend into June or July. They perform well in cold climates, but can be sensitive to heat and show some heat stress in mid-summer. However, when temperatures fall again in autumn, often they put on new growth that lasts to the next season. Some of spreading varieties that have performed very well in our three-year trials include Dianthus ‘Kahori’, which won a top performer award in our trials in 2017. Other performers that look promising in our trials after one winter are ‘Mountain Frost’ from Darwin Perennials and the new ‘Kahori’ series from Dummen Orange. Dianthus Trials at Colorado State University CSU RESEARCH UPDATE By James E. Klett, Ph.D. Professor & Extension Horticulturist & David McKinney Horticulture & Environmental Horticulture Undergraduate Student Dianthus ‘Mountain Frost Pink Twinkle’ Dianthus ‘Mountain Frost Pink PomPom’ Dianthus ‘Mountain Frost White Twinkle’ Dianthus ‘Sunflor Desire’ Dianthus ‘Kahori Scarlet’ Dianthus ‘Kahori’ Dianthus 'Kahori'