Potassium Deficiency in Palms - Manatee County Extension Office

ENH1017Potassium Deficiency in Palms 1Timothy K. Broschat 2SymptomsSymptoms of potassium (K) deficiency varyamong species, but always appear first on the oldestleaves. Older leaflets of some palms such asDictyosperma album (hurricane palm) are mottledwith yellowish spots that are translucent whenviewed from below (Figure 1). In other palms suchas Dypsis cabadae (cabada palm), Howea spp.(kentia palms) and Roystonea spp. (royal palms),symptoms appear on older leaves as marginal or tipnecrosis with little or no yellowish spotting present(Figures 2 and 3). The leaflets in Roystonea, Dypsis,and other pinnate-leaved species showing marginal ortip necrosis often appear withered and frizzled.In fan palms such as Livistona chinensis(Chinese fan palm), Corypha spp. (talipot palm),Washingtonia spp. (Washington palms), andBismarckia nobilis (Bismarck palm), necrosis is notmarginal, but is confined largely to tips of the leaflets(Figures 4 and 5). In Phoenix roebelenii (pygmy datepalm), the distal parts of the oldest leaves aretypically orange with leaflet tips becoming necrotic(Figure 6). The rachis and petiole of the leavesusually remains green, however, and the orange andgreen are not sharply delimited as with magnesiumFigure 1. Older K-deficient leaf of Dictyosperma albumshowing translucent yellow-orange spotting when held upto the light. Credits: T.K. Broschat(Mg) deficiency. This pattern of discoloration holdsfor most palm species that show discoloration as asymptom.In Phoenix canariensis (Canary Island datepalm), leaflets show fine (1-2 mm) necrotic andtranslucent yellow spotting and extensive tipnecrosis. These necrotic leaflet tips in most Phoenixspp. are brittle and often break off, leaving themargins of affected leaves irregular.1. This document is ENH1017, one of a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food andAgricultural Sciences, University of Florida. Original publication date September 2005. Reviewed: September 2008. Visit the EDIS Web Site athttp://edis.ifas.ufl.edu.2. Timothy K. Broschat is Professor, Environmental Horticulture Department, Fort Lauderdale Research and Education Center, Institute of Food andAgricultural Sciences, University of Florida, Fort Lauderdale, FL 33314The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information andother services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex,sexual orientation, marital status, national origin, political opinions or affiliations. U.S. Department of Agriculture, Cooperative Extension Service,University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. LarryArrington, Dean

Potassium Deficiency in Palms 2Figure 2. Potassium-deficient older leaf of Dypsis cabadaeshowing necrosis and curling of leaflet tips. Credits: T.K.BroschatFigure 5. Potassium-deficient older leaf of Livistonachinensis showing leaf discoloration. Credits: T.K. BroschatFigure 3. Potassium-deficient older leaf of Roystonearegia showing leaflet tip necrosis and curling. Credits: T.K.BroschatFigure 4. Potassium-deficient older leaf of Washingtoniarobusta showing extensive leaflet tip necrosis. Credits: T.K.BroschatIn Caryota spp. (fishtail palms) and Arenga spp.(sugar palms), chlorotic mottling is minimal ornon-existent, but early symptoms appear as irregularnecrotic spotting within the leaflets (Figures 7 and 8).Figure 6. Potassium deficiency of Phoenix roebelenii.Credits: T.K. BroschatIn most other palms, including Cocos nucifera(coconut palm), Elaeis guineensis (African oil palm),Dypsis lutescens (areca palm), Chamaerops humilis(European fan palm) Hyophorbe verschafeltii(spindle palm), and others, early symptoms appear astranslucent yellow or orange spotting on the leafletsand may be accompanied by necrotic spotting aswell. As the deficiency progresses, marginal and tipnecrosis will also be present. The most severelyaffected leaves or leaflets will be completely necroticand frizzled except for the base of the leaflets and therachis (Figures 9-11).For all palms, symptoms decrease in severityfrom tip to base of a single leaf and from old to newleaves within the canopy (Figures 12 and 13). Insevere cases, the entire canopy will consist of areduced number of leaves, all of which will bechlorotic, frizzled, and stunted (Figures 14 and 15).The trunk will begin to taper (pencil-pointing) anddeath of the palm often follows.

Potassium Deficiency in Palms 3Figure 7. Potassium-deficient older leaf of Arenga sp.Credits: T.K. BroschatFigure 10. Potassium-deficient older leaf of Chamaeropshumilis showing translucent orange and necrotic spotting.Credits: T.K. BroschatFigure 8. Potassium-deficient older leaf of Caryota mitis.Credits: T.K. BroschatFigure 11. Potassium deficiency symptoms on older leaf ofCocos nucifera showing translucent yellow-orangespotting. Credits: T.K. BroschatFigure 9. Potassium-deficient older leaf of Dypsislutescens showing leaf discoloration and extensivenecrosis of the leaflet margins and tips. Credits: T.K.BroschatCausePotassium deficiency is caused by insufficient Kin the soil, but can be induced or accentuated by highN:K or Ca:K ratios in the soil. Potassium is readilyFigure 12. Potassium-deficient older leaf of Cocosnucifera showing progression of symptoms from the baseto the tip of the leaf. Credits: T.K. Broschatleached from sand or limestone soils which have verylow cation exchange capacities.

Potassium Deficiency in Palms 4Figure 13. Potassium-deficient Hyophorbe verschafeltiishowing the increase in severity of symptoms from new toold leaves. Credits: T.K. BroschatFigure 15. Late stage K deficiency in Roystonea regiashowing small necrotic leaves and tapering trunk(pencil-pointing) Credits: T.K. Broschatgenera such as Veitchia, Ptychosperma, Adonidia, andArchontophoenix are notably resistant to Kdeficiency. Potassium deficiency is the leading causeof mortality in Roystonea growing in southern Floridalandscapes.Diagnostic TechniquesVisual symptoms alone may be sufficient fordiagnosis of this disorder although leaf nutrientanalysis may be helpful in distinguishing late stage Kdeficiency from manganese (Mn) deficiency. Thesetwo deficiencies can be extremely similar from adistance, but close examination should revealcharacteristic spotting and marginal necrosis in Kdeficiency or necrotic streaking for Mn deficiency.Potassium deficiency symptoms are also more severetoward the leaf tip and are less so at the leaf base.The reverse is true for Mn deficiency.Figure 14. Late-stage K deficiency in Cocos nuciferashowing small chlorotic and necrotic new leaves and trunktapering. This palm died shortly after the photo was taken.Credits: T.K. BroschatOccurrencePotassium deficiency is very common on palmsgrown in highly leached sandy soils. It is lesscommon in container substrates. Potassiumdeficiency is perhaps the most widespread of all palmnutrient deficiencies, occurring in most palm-growingregions of the world. It is quite severe in southernFlorida and much of the Caribbean region. Althoughmost species of palms are susceptible to some degree,When sampling for leaf analysis, select 4 to 6central leaflets from the youngest fully-expandedleaf. Soil analysis is not particularly useful fordiagnosing palm nutrient deficiencies, since palmnutrient symptomology often bears little resemblanceto soil nutrient profiles.ManagementRegular applications of K fertilizers will preventK deficiency and treat palms already deficient. Onsandy soils, or those having little cation exchangecapacity, controlled-release K sources are much moreeffective than the easily leached water-soluble Ksources. Sulfur-coated potassium sulfate has been

Potassium Deficiency in Palms 5shown to be the most effective and economicalsource for K in the landscape. When applying Kfertilizers to correct an existing K deficiency, it isimportant to also apply about 1/3 as much Mg (alsoin a slow release form such as prilled kieserite) toprevent a high K:Mg ratio from causing an Mgdeficiency problem. For severely K-deficientlandscape palms, broadcast this 3:1 blend ofsulfur-coated potassium sulfate and prilled kieseriteuniformly to the soil under the canopy at a rate of 1.5lbs per 100 sq ft of canopy area. This should berepeated in three months. Three and six months afterthat, a 1:1 mixture of the K:Mg blend and a balanced8-2-12+4Mg palm maintenance fertilizer should besimilarly applied at the rate of 1.5 lbs of fertilizer per100 sq ft of canopy area, bed area, or entire landscapearea. After one year, use only the 8-2-12+4Mg withmicronutrients maintenance fertilizer at the aboverate.culture. J. West African Inst. Oil Palm Res.3:254-264For mild to moderately K-deficient palms,application of the 8-2-12+4Mg palm maintenancefertilizer every 3 months should be sufficient to treatand prevent K deficiencies. Treatment of K deficientpalms may require one to two years or longer, sincethe entire canopy of the palm may need to be replacedwith new symptom-free leaves. Removal ofdiscolored older K-deficient leaves on a regular basishas been shown to accelerate the rate of decline fromthis disorder and can result in premature death of thepalm.See also ENH 1009 and ENH1010Selected ReferencesBroschat, T.K. 1984. Nutrient deficiency symptomsin five species of palms grown as foliage plants.Principes 28:6-14.Broschat, T.K. 1990. Potassium deficiency of palmsin south Florida. Principes 34:151-155.Broschat, T.K. 1994. Removing potassium deficientleaves accelerates rate of decline in pygmy datepalms. HortScience 29:823.Bull, R.A. 1961. Studies on the deficiency diseasesof the oil palm. 2. Macronutrient deficiencysymptoms in oil palm seedlings grown in sand