PPDL Picture of the Week for
February 18, 2013

Improving Rooting of Challenging Yellow Petunia Cultivars

Roberto G. Lopez, Associate Professor & Floriculture Extension Specialist, Purdue University

Have your yellow petunia cuttings rooted well, and then suddenly lost vigor, turned yellow, developed brown shoot tips, and/or died (Fig. 1). You’re not alone, if fact this has been an issue for growers over the past several years.

Research conducted at Ball Horticulture Co. and Purdue University has revealed that nutrition of petunia is very important during rooting, especially of those challenging cultivars. Cuttings must have ample nutrition available in the substrate 4 to 6 days after stick, when roots begin to form in order to avoid the problems we have illustrated. Therefore, cuttings of yellow petunia cultivars should be rooted using an aggressive fertilizer program that supply not only higher levels of nitrogen, but micronutrients as well.

Click image to enlarge

Figure 1. Growers have found that cuttings of some yellow petunia cultivars often root well, but toward the end of the liner rooting stage they can lose vigor, turn yellow, develop necrotic (brown) shoot tips, and/or die (top) compared to other cultivars (bottom).

Figure 2. As substrate incorporated with controlled release fertilizer (CRF) increased from 0 to 15 g⋅L−1 or 60 ppm water soluble fertilizer (WSF), the visual quality of rooted yellow petunia increased from severe necrosis or death to green, little or no yellowing or necrosis. Photo taken three weeks after sticking.

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service