Rich Hollenbach & Sarah Mitchell
Photo courtesy of Green Leaf Plants®

During the summer peak, Green Leaf Plants® harvests 500,000 unrooted Dianthus cuttings per week from clean stock. Rich Hollenbach, production planning inventory control manager, and Sarah Mitchell, greenhouse operations and new product development manager, discuss how to care for this genus.

Greenhouse Management: Why should growers add Dianthus to their product mix?

Rich Hollenbach: Dianthus is in high demand, and growers can meet specific production windows and make a profit. With 99 varieties in our offering, this is a signature crop for Green Leaf Plants®. We’ve worked with breeders like Whetman® Pinks Ltd. from the U.K. and PlantHaven since the 1990s. Breeders worldwide bring us double flowers, bicolor flowers, wild colors, spicy scents. The neat foliage choices are steely blue to warm green. Consumers are simply responding to beautiful varieties that are hardy in many U.S. and southern Canadian markets.

GM: What are some of the Dianthus varieties and shades that are trending with customers?

Sarah Mitchell: While breeders have delivered a palette of new colors, flower forms and habits for nearly every consumer preference, we also look for staying power in the garden. The Whetman® Pinks Ltd. new American Pie™ Collection, is gaining traction while the Star series remains the benchmark for performance. Pink PomPom from the Mountain Frost™ Collection blooms nonstop. SuperTrouper™ and Oscar® series are predictable in the greenhouse. Vivid™ Bright Light is small but mighty, reblooming spring through fall.

GM: What advice would you give growers on selecting the best Dianthus varieties for their operation?

SM: While gardeners love new flowers, growers want hardy varieties with uniform crop schedules. As a general rule, narrow leaf varieties tend to be hardier than broader leaf cultivars. Crop timing is more consistent within one breeding line than a collection of cultivars. It is very difficult to choose varieties from a catalog. We have new trial beds of Dianthus to test cold hardiness, heat tolerance and flower timing for the Mid-Atlantic region. A Dianthus Production Guide is available with tips. Of all the Dianthus offered, Firewitch — a rugged variety in the public domain — remains the most popular. 

GM: What are some of the biggest challenges growers face in Dianthus production?

RH: Dianthus is susceptible to many viruses. Deviating from strict sanitation protocols can cause real trouble in a short period of time. Always purchase cuttings or liners from producers who start with elite, virus-free plants. These growers have rigorous sanitation practices and check routinely for disease.

GM: How do foliage and rooting habits differ between different Dianthus varieties?

SM: Typically, broader leaf varieties grow faster and flower quicker than narrow leaf varieties. Vernalization is required for some cultivars. New breeding is reducing the dormancy requirement. However, even a few weeks under 45° F promotes more flowers per pot and improves plant quality. — Interviewed by Patrick Williams

For more information, reach Green Leaf Plants® experts by email at rich.hollenbach@GLPlants.com and sarah.mitchell@GLPlants.com, or request the Dianthus Production Guide at GreenLeaf@GLPlants.com