Alert by Brian E. Whipker1 ([email protected]) Volume 3, Number 45 August 2014 Ornamental Cabbage and Kale: Avoiding Lower Leaf Loss Curtailing fertilization results in lower leaf yel- lowing, leaf loss, and poor quality plants. Center head coloration is enhanced with temperatures below 55F (13C) and not by discontinuing fertil- 2014 Sponsor ization. Ornamental cabbage and kale (Brassica oleracea var. acephala L.) are major fall crops for many grow- ers. The colorful foliage and added height make the plants a nice compliment to fall pansies. Fertilizer recommenda- tions vary, and there are suggestions that fertiliza- tion should be discontin- ued to enhance center head development. This practice has been proven to be incorrect based on research from the Master’s degree work by Dr. Jamie Gibson (currently Technical © Brian Whipker © Brian 1 Department of Horticultural Figure 1. Continual fertilization is required for ornamental cabbage and kale Science, NC State University to avoid lower leaf loss. e-GRO Alert - 2014 e-GRO Alert Specialist with Syngenta one should target the low- Flowers) at North Carolina er end of the fertilization www.e-gro.org State University and obser- range, while the higher vation of growers’ crops. end of the range will result CONTRIBUTORS A fertilization strategy in larger plants. Fertiliza- Dr. Nora Catlin that avoids lower leaf loss tion rates for sub-irrigated Floriculture Specialist Cornell Cooperative Extension - and produces high quality plants are 25% lower. Slow Suffolk County [email protected] plants is discussed. release fertilizer can also be used. Plants can be Dr. Kristin Getter Floriculture Outreach Specialist Fertilization grown over a pH range be- Michigan State University For the seedling stage, tween 5.5 and 6.2. If the [email protected] fertilize at the rate of 50 pH exceeds 6.5, iron can Dan Gilrein to 100 ppm of N with a be tied up, thus becoming Entomology Specialist Cornell Cooperative Extension - constant liquid feed. Af- unavailable to the plant, Suffolk County ter transplanting into the [email protected] being manifested as an Dr. Brian Krug Floriculture Ext. Specialist with a balanced fertil- interveinal chlorosis of the Univ. New Hampshire izer at a concentration upper leaves. [email protected] of 150 to 250 ppm N and Dr. Joyce Latimer K. Electrical conductivity Ornamental cabbage and Floriculture Extension & Research Virginia Tech (EC) should be maintained kale can readily exhibit [email protected] between 1.0 and 2.5 mS/ - Dr. Roberto Lopez cm during periods of ac- cient levels of fertility will Floriculture Extension Specialist & Research tive growth. If the goal is result in yellowing (nitro- Purdue University to minimize plant growth, [email protected] Dr. Paul Thomas Floriculture Extension & Research University of Georgia [email protected] Fertilization Strategy by Growth Stage Dr. Brian Whipker Development Stage Nitrogen Fertilization Rate Floriculture Extension & Research NC State University Seedling 50-100 ppm N [email protected] Active Growth 150-250 ppm N Head Coloration 100-200 ppm N Copyright © 2014 are listed, no discrimination is intended and no endorsement, guarantee or warranty is implied by the authors, universities or associations. Fertilization of Ornamental Cabbage and Kale Video http://www.greenhousegrower.com/video/varieties/v- coloring-up-and-avoiding-lower-leaf-loss-in-kale-and- cabbage/ 2 e-GRO Alert - 2014 Cooperating Universities NC STATE UNIVERSITY Floriculture © Brian Whipker © Brian In cooperation with our local and state greenhouse organizations © Brian Whipker © Brian Figure 3. Severe symptoms of lower leaf yellowing and drop due to low EC. 3 e-GRO Alert - 2014 © Brian Whipker © Brian Figure 4. Advancing symptoms of lower leaf discoloration (pale red, yellow, and brown) and loss due to curtailing fertil- ization. To subscribe to e-GRO Alert, go to: www.e-gro.org and click on the subscribe button 4 e-GRO Alert - 2014 In contrast, discontinuation of the basal leaves. Orna- of all fertilization has a symptoms and lower leaf mental cabbage and kale detrimental effect on plant loss. So by continuing to also have an above aver- - fertilize ornamental cab- age requirement for sulfur, toms can quickly occur in bage and kale with 100 to so monthly applications of a soilless substrate, which 200 ppm during head color- Epsom salts at 1 pound per has a low cation exchange ation will avoid lower leaf 100 gallons of water, ap- capacity (the ability to discoloration and loss. plied as a irrigation with hold nutrients). In one of a 10% leaching fraction the NCSU studies, we ob- Summary should be made. served that after only 2 Head color development in weeks of discontinuing fer- ornamental cabbage and Excessive fertilization can tilization of market ready kale is primarily induced result in a marginal tip plants, that the EC values by temperatures below 55F burn. Tip burn is more dropped by 90%, and leaf (13C). The common belief prevalent if the plants tissue values for N, P, and that discontinuing fertiliza- were allowed to wilt. K decreased by 37%, 40%, tion is will enhance color- A high EC and excessive and 30%, respectively, in ation is incorrect. Instead, drought stress can also re- comparison to fertilized plants are still increasing sult in lower leaf loss and plants. We have observed in mass, so discontinu- root death. with grower samples that ing fertilization actually induces lower leaf yellow- Center Color Enhance- were present when root ment substrate EC readings were of nitrogen. Lower leaf The production practice of <0.30 mS/cm (SME ex- loss and naked stems can discontinuing fertilization tract). quickly follow which will once the plants have sized lower the overall crop up to enhance color devel- Discontinuing fertiliza- quality. Therefore growers opment is still being used. tion 2 weeks before sales should continue to fertilize Research conducted at results in plants becoming ornamental cabbage and North Carolina State Uni- kale during color develop- versity indicate that exces- plants are still actively de- ment at 100 to 200 ppm N sive fertilization greater veloping during this period to maintain plant quality. than 250 ppm N will mute and increasing in size (dry the overall intensity of weight). If fertilization is color development, but not provided, the plants plants still develop color. reallocate mobile elements Coloration is primarily en- such as N, P, and K from hanced by cooler growing the lower leaves to the temperatures below 55F upper leaves. This leads to (13C). the appearance of lower 5.