Finch, Calvin

Janne, Everett E.

Welsh, Douglas F.

English

Texas A&amp;M Repository

L -1097exas Agricultural Extension Service®®[p) Environmentally Safe PracticesFERTILIZING WOODY ORNAMENTALSDouglas F. Welsh, Everett E. Janne and Calvin Finch*Attractive trees and shrubs are important com-ponents in all well-landscaped properties. Planned main-tenance and care are essential for keeping them healthyand vigorous. An adequate fertilization program is an im-portant requirement of any good woody-plant main-tenance program. It is important, however, that plantsnot be overfertilized and that fertilizer not be expected toovercome problems caused by the use of unadaptedvarieties, improper planting techniques, poor soildrainage, soil compaction or incorrect watering prac-tices.In many yards, a good lawn maintenance programmay eliminate the need for supplemental fertilization fortrees and other woody plants in the lawn. Additional fer-tilizer would simply be a waste of money and might resultin nutrient imbalances or pollution of local water supplies.Occasionally, additionaf fertilizer is needed in areaswhere a tree's root growth is restricted by streets, curbsor other structural features. Shrubs and vines frequentlyserve as screens or borders for lawn areas within thelandscape. Consequently, these plants are frequently for-gotten or neglected in the normal lawn fertilization pro-gram.Plant signs indicating the need for fertilization includelack of terminal growth, pale green or yellow leaves, mot-tled leaves, dead branches, stunted leaves and early lossof leaves.General tree vigor is determined by compari~g thelength of twig growth during the past 3 to 4 years (Figure1). Young trees should have at least 9 to 12 inches of ter-mina growth per year. Large mature trees usually* Extension Horticulturist, Extension Horticulturist (retired) andExtension assistant, The Texas A&M University System.average 6 to 9 inches of growth. Shrub vigor is deter-mined the same way. Growth varies from season toseason and from variety to variety. It also depends onthe species and size being examined.Figure 1. The distance between bud scale scarsprovides an excellent indication of a tree's growthrate. The ring of scars near the branch tip showswhere growth started last spring~ The bud scarsnear the .base of the branch denote where theprevious season's growth started. By locating budscars for the past 3 to 4 years the rate of growth canbe determined readily.Obtain a Soil or Foliar AoafySisFertilizer recommendations should be based on asoil and/or foliar analysis. Instructions for taking a soil orleaf sample can be obtained from the county Extensionoffice. Such analyses allow the application of fertilizersin amounts and ratios that minimize nutrient waste andthe threat of pollution.exas ricultural Extension Service • The Texas A&M University System • Zerle L. Carpenter, Director • College Station, TexasWithout such analyses, general lawn fertilizer recom-mendations of 4 to 6 pounds of actual nitrogen per 1,000square feet per year will meet the needs of most treesand shrubs. In turf areas, do not apply this amount atone time but rather make several applications to preventfertilizer burn of the turf.similar ratio are readily available, including 10-8-6 and 12-6-6. If the desired ratio is unavailable, a 3-1-1 ratio fer-tilizer can be approximated by mixing 12 ounces of am-monium nitrate (33-0-0) to each pound of a 12-12-12 fer-tilizer. The same type fertilizer can be used on shrubsand vines (Table 1).Proper timing of fertilizer applications has a markedeffect on the growth of woody plants. In general, thebest time to apply fertilizer is in the spring before growthbegins.Table 1. The amount of nitrogen fertilizers needed tosupply 1 to 2 pounds of actual nitrogen per 1,000square feet.Computing Amount of Fertilizer NeededTo figure the amount of nitrogen-containing fneeded for woody plants, stake off a square or rectan-gular area that includes the entire branch spread of thetrees and shrubs in an area. If roots are restricted bypavement, curb or a building, subtract the restricted areafrom the total area computed (Figure 2).Application MethodResearch shows that when fertilizing trees andshrubs, surface applications of nitrogen-containing fer-tilizers are as efficient as the old method of punchingholes. Fertilizer may be dist~ibuted by hand or with a fer-tilizer spreader. Distribute the fertilizer evenly and avoidskips and overlapping which result in light and darkstreaks in grass growing beneath the trees. To obtaineven distribution, divide the fertilizer into two equal lots46102016201620122016101/22Ib N23510810810610851/4.Approximate pounds of fertilizerneeded to supply1lb NMaterialUrea (45-0-0)Ammonium nitrate (33-0-0)Ammonium sulfate (21-0-0)10-10-1012-12-1210-20-1012-6-610-5-516-20-015-5-1012-4-819-5-9Soil type also affects the timing of fertilizer applica-tions. For sandy or loam soils, apply fertilizer as soiltemperatures begin to rise and before growth occurs.For heavy clay soils apply the fertilizer in late fall afterleaves have fallen or the plant is completely dormant.Do not apply fertilizers from August 1 until late fall(about the time of the average date of the first killingfrost). Late summer fertilizing can stimulate an excessiveamount of new growth, making plants more susceptibleto winter injury. In South Texas where freeze damage isslight, late summer fertilizer applications are beneficialand provide needed nutrients for late fall and wintergrowth.Most fertilizers are purchased according to theiranalysis which is the percentage of the three major plantnutients - nitrogen, phosphorus and potassium. Theanalysis is shown on the bag or container and consistsof three numbers (i.e., 12-4-8). The first number indi-cates the percentage of nitrogen (N), the second givesthe percentage of phosphorus as phosphoric acid(P20S); and the third is the percentage of potassium aspotash (K20). A 50-pound bag of a 12-4-8 fertilizer con-tains 6 pounds of N, 2 pounds of P20S and 4 pounds ofK20.The maximum growth response to the fertilizer is ob-tained if the fertilizer is available in the root zone at orslightly before the start of spring growth. In sandy soilsfertilizer moves more rapidly into the root zone, whereasin heavy soils, it takes much longer for the fertilizer topenetrate.Tree growth' is limited by nitrogen deficiency moreofter. than by lack of phosphorus or potassium. For thisreason, it is recommended that a fertilizer with a 2-1-1 or3-1-1 ratio be used for trees. Fertilizers with a 2-1-1 orPavedarea0-- StakeL4=--~--- Tree roots" .",......._------"30Feet~>---------40 FeetFigure 2. Stake off a square or rectangle that includes all the branch area not over paved surface. In this examplefertilizer is needed for a 1,200 square-foot area.and apply one-half lengthwise over the area and theremainder crosswise over the area. Water the areathoroughly after fertilizing, soaking the soil to a depth ofat least 6 inches.Table 2. Amounts of phosphorus and potassiumfertilizer materials needed to supply 3.6 pounds P20Sper 1,000 square feet and 6 pounds of potash (K2)per 1,000 square feet.If soil or foliar analyses indicate a need for eitherphosphorus or potassium, place fertilizer in holes ratherthan on the surface because these materials penetratetoo slowly to reach tree roots in adequate amounts whensurface applications are made. Phosphorus or potas-sium applications are needed only every 3 to 5 years. Inmost areas of Texas, except possibly in the acid soils ofEast Texas, the amount of phosphorus and potassium inthe soil is sufficient to adequately supply the needs ofwoody plants. Check with your county Extension officebefore applying additional phosphorus or potassium.See Table 2 for the amount of phosphorus and potas-sium-containing materials to use per 1,000 square feet ofarea if required.MaterialPhosphorus (P)Superphosphate(0-20-0)Triplesuperphosphate(0-46-0)Potassium (K)Muriate of potash(0-0-60)Quantity Amount per holeneeded per based on 250 holes1,000 sq ft per 1,000 sq ft181b 2 tbsp81b 1 tbsp10lb 1 tbspNitrogen, phosphorus,potassium10-20-1012-12-12181b30lb1/4 cup1/2 cupFertilizing Evergreens in Alkaline SoilsEvergreen plants generally require less fertilizer thandeciduous plants. Most broad-leaved evergreens (mag-nolia, loquat, photinia, etc.) prefer an acid soil. To main-tain these conditions, use acid-type fertilizers and avoidmaterials such as wood ashes, lime, fresh manure orbonemeal.Sometimes organic fertilizers are preferred for usearound broad-leaved evergreens. Nutrients in thesematerials are released to the plant slowly and do notproduce excessive growth. There is less danger ofdamage from overfertilization. Apply fertilizers such ascottonseed or soybean meal at 5 to 6 pounds per 100square feet of planted area. Another organic-type fer-tilizer can be prepared using one part by weight of sul-fate of potash or muriate of potash; two parts by weightof 20 percent superphosphate; and five parts by weightof cottonseed meal. Thoroughly mix the materials andapply at a rate of 2 to 5 pounds per 100 square feet ofarea under the trees or shrubs. Apply the fertilizer mix tothe surface or work into the top few inches of soil, avoid-ing injury to the roots. One application every other yearusually is adequate.In general, the procedure previously outlined for fer-tilizing other woody plants is adequate for narrow leavedevergreen trees but reduce the amount by one-third. Forbest results, apply in early spring before growth starts.MicronutrientsThe micronutrient most commonly deficient in Texassoils is iron. This deficiency usually is noted in alkalinesoil regions. The iron becomes insoluble and the plantcannot extract sufficient amounts from the soil for goodgrowth. Iron deficiency symptoms include pale green toyellow leaves with darker green venation. It is very com-mon on plant species not adapted to alkaline soils includ-ing some of the red oaks, maples and hollies.Iron deficiency can be corrected partially with foliarapplications of chelated iron provided label recommenda-tions are followed. If the soil is only slightly alkaline, usesoil applications of iron sulfate or sulfur.In general, woody plants adapted to the local areaare usually very effective for growing in landscapedareas with well-maintained lawns. In the event thatnutrient deficiencies occur, the practices describedabove will aid in maintaining strong, healthy trees.Protect the EnvironmentFertilizer applied in excess of plant needs or with im-proper timing often goes to waste. In the case ofnitrogen, the excess material may quickly leach into thesubsoil and result in pollution of underground water sup-plies.To reduce pollution of surface water supplies (Le.,rivers and lakes), minimize the amount of fertilizer whichends up in the storm sewer by keeping fertilizer off thepavement and driveways. A small amount of runoff fromeach yard can add up to a major pollution problem for acity.Insure efficient fertilizer use by following fertilizerrecommendations based on soil and/or foliar analysis.This will prevent applying excess nutrients, causingnutrient imbalances and poor plant health.ESP, Environmentally Safe Practices, is a Texas Agricultural Extension Service program designed topromote the use of safe practices around the home and landscape. Whether one is working inhousehold activities, home landscaping and gardening or in production agriculture, environmentallysound practices should be used. It is the responsibility of our generation to make wise use ofenvironmental resources and to extend the use to future generations.This publication was made available through Extension Service-United States Department ofAgriculture funding in cooperation with the Texas Agricultural Extension Servic~.HORT 4-5he information herein is for educational purposes only. Reference to commercial prOducts or trace names IS made with the understanding that noiscrimination is intended and no endorsement by the Cooperative Extension Service is implied.educational programs conducted by the Texas Agricultural Extension Service serve people of all ages regardless of socioeconomic level, race, color,se~, religion, handicap or national origin.Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, as amended, and June30, 1914, in cooperation with the United States Department of Agriculture. Zerle L. Carpenter, Director, Texas Agricultural Extension Service, TheTexas A&M University System.10 M--9-89, Revision

Fertilizing Woody Ornamentals.

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Fertilizing Woody Ornamentals.

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Fertilizing Woody Ornamentals.

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