Why are our HOA's trees turning yellow with green veins, and how do we treat iron chlorosis?

By OurHOA · General information · Revised October 31, 2026

How an HOA board diagnoses and treats iron chlorosis in yellowing common-area trees and shrubs: soil pH tests, watering fixes, iron chelates and tolerant trees.

Part of the HOA board handbook: vendors, projects and upkeep.

What the yellow leaves mean and what to do

Leaves that turn yellow while the veins stay green, starting at the branch tips, are the classic sign of iron chlorosis. The soil usually has plenty of iron. Alkaline soil locks it into a form the roots cannot take up, and wet or compacted soil makes it worse. Colorado State University (CSU) Extension and Utah State University Extension, both writing for high-pH soils like the Front Range's, give the same order of work. First, confirm the diagnosis and test the soil pH. Second, fix the watering, compaction and planting problems that starve roots of oxygen. Third, treat the trees worth saving with the right iron product at the right time of year. Fourth, stop planting species that cannot cope with your soil. Iron treatments buy time, anywhere from a few weeks to a few years depending on the method. None of them changes the soil. Rules and maintenance duties vary by state and by your governing documents. This guide is general education, not legal advice.

Confirm it before you buy iron

CSU GardenNotes #223 (reviewed July 2023) describes the pattern. Yellow tissue appears between green veins, first on new growth at the branch tips. In bad cases leaves turn pale yellow or nearly white, with brown spots between the veins and scorched edges, and they may stay small, curl and drop. Chlorosis often shows on one branch or one side of a tree. On junipers, pines and other evergreens it tends to look like general yellowing of the needles. A Texas A&M AgriLife Extension horticulture agent in Bexar County points out the contrast with a nitrogen shortage, which starts on the older leaves at the bottom of the plant. Utah State says to rule out insects, disease, herbicide damage and overwatering before treating. It also warns that high pH can cause manganese deficiency, which looks almost the same. Before the board spends money on treatment: - Have the landscape committee photograph the affected trees and mark them on the common-area tree map. - Send soil from the root zone of two or three of the worst trees to a soil testing lab, such as the one your county Extension office uses. Ask for pH and free lime (calcium carbonate). - If the pH is above 7.5, chlorosis is the likely cause. If it is near neutral, look harder at roots, disease and herbicide use nearby. - If the pattern doesn't match, take a bagged sample branch to the county Extension office.

Why it shows up in Colorado and Texas common areas

CSU says many Colorado soils are calcareous, with a pH above 7.5, and that above pH 7.0 iron gets fixed into insoluble forms. The Bexar County article says the same about Texas. Chlorosis turns up where soils are highly alkaline, and high soil temperatures and strong light make it worse. It names red tip photinia, Indian hawthorn, pines and St. Augustinegrass as common sufferers there. Utah State adds that carbonates from irrigation water can build up over time, so a bed can get worse year after year with no change in planting. What tips a borderline tree into decline is often something the association controls. CSU lists wet springs and spring overwatering as key factors, and says sprinkler settings left unchanged can put down up to 40 percent more water than plants need in spring and fall. Compacted clay, crusted soil and plastic sheeting under rock mulch all cut off oxygen. Trees planted too deep grow girdling roots, and CSU says chlorosis can be an early sign of them. CSU's PlantTalk adds that too much phosphorus fertilizer can set it off, because roots take up the phosphorus at the expense of iron.

Fix the water and the roots first

These steps cost little, and every treatment that follows works better because of them. - Reset the irrigation zones that water trees and shrubs. Spring and fall run times should be well below summer run times, and zones under yellowing trees should dry out between cycles. Our guide on cutting an HOA water bill with an irrigation audit shows how to check what each zone actually puts down. - Tell the landscaper to stop using high-phosphorus fertilizer in beds and around affected trees unless a soil test calls for it. - Pull up plastic sheeting under rock or bark. Utah State says not to use plastic as mulch, and CSU says organic mulch helps. - Aerate compacted soil around affected plants, as Utah State recommends, and pull turf back from trunks where you can. - Have an arborist check the worst young trees for planting depth and girdling roots at the root flare. Give these changes a full growing season before you judge them.

Iron treatments, from fastest to longest lasting

Foliar sprays. Spraying leaves with iron sulfate or a chelate gives the quickest response, often within days, according to both CSU and Utah State. The greening is spotty and temporary, and it may need repeating within the season. Utah State gives a 0.5 percent ferrous sulfate solution, 2 ounces in 3 gallons of water, sprayed in the evening or on a cool, cloudy day to avoid leaf burn. Both say sprays are impractical on large trees, so keep them for shrubs and small ornamentals. CSU warns that iron sulfate overspray can stain concrete and brick permanently. Soil-applied chelates. Chelated iron in the root zone can work fast if the chelate matches the soil. CSU says that above pH 7.5 you need EDDHA (such as Sequestrene 138) or EDDHMA products, because EDTA and DTPA products lose effectiveness above about pH 7.2 to 7.5. CSU says applications after May 1 are less likely to work, and Utah State says to apply in spring before growth begins. CSU says results last from less than one season to two years, and Utah State says about one. CSU's method is holes 1.5 to 2 inches across and 6 inches deep, 12 inches apart, in rings 2 feet apart, keeping 2.5 to 4 feet away from the trunk of established trees. CSU also says to call 811 before anyone digs. Iron sulfate with sulfur. A mix of equal parts iron sulfate and elemental sulfur can last 2 to 4 years, per Utah State. CSU says it only makes sense on soil with no free lime, and that lowering soil pH with sulfur seldom merits consideration in Colorado. Your soil test settles this. Trunk injections and implants. An arborist drills small holes in the trunk and puts iron straight into the tree. CSU says effects last one to five years, and Utah State says two or more. The price is a wound. Both warn the holes can let in decay. Utah State says to use the smallest holes possible, inject in early spring around bud break, and not re-inject more often than every few years. CSU's PlantTalk says injections are best left to certified arborists. Save them for large, valuable trees, such as the shade trees at the entrance or the pool.

Stop replanting the trees that fail

CSU's PlantTalk puts it plainly. Where soil pH is above 7.5, the best control for iron chlorosis is to avoid trees that are sensitive to alkaline soils. CSU's lists of susceptible plants include red, silver and Amur maple, pin and red oak, aspen, apple and crabapple, pear, linden, magnolia, birch, beech, spruce, pine, juniper, rhododendron and azalea. Utah State says silver maple and quaking aspen have serious problems on high-pH sites and should be avoided there. In Texas, the Bexar County article adds photinia and Indian hawthorn. That should change your planting rules. Add a line to the landscape plan or design guidelines saying common-area replacements come from a high-pH-tolerant list the landscape committee approves. Build it with your county Extension office or a local arborist. When a tree has been treated for several years and still declines, budget for replacement instead of another round of injections. Our guide on planning an HOA tree maintenance program shows how to fold that decision into the yearly tree walk.

Bid wording, a sample year and common mistakes

Bid request: "Provide a price to treat iron chlorosis on the trees and shrubs listed on Exhibit A. State the product and active ingredient (for soil-applied chelates, the chelate type, such as EDDHA), the application method, the timing, and how long you expect the result to last. For trunk injections, state the hole size and the number of injection sites per tree. Attach the soil pH result you relied on for each site." Motion: "Move that the association test soil pH at [number] common-area sites at a cost not to exceed $[amount], reset spring and fall irrigation schedules for the tree and shrub zones, and ask the landscape committee to return with treatment bids and a high-pH-tolerant replacement list by [date]." A sample year. July and August, when symptoms are easy to see: map the affected trees. September: soil tests and an irrigation check, with fall run times cut back. October to February: get bids and decide which trees to treat, replace or leave alone. March and April, before or around budbreak: soil chelates and trunk injections. Summer: foliar sprays on shrubs if needed, and a note of which trees greened up. Common mistakes: buying iron before testing the soil, using an EDTA or DTPA product on soil above pH 7.5, putting soil iron down in summer, leaving the sprinkler clock on summer settings in spring and fall, feeding beds high-phosphorus fertilizer, injecting the same trees every year, letting iron spray stain the entrance monument, and replacing a dead pin oak with another pin oak.

Sources

These guides are general education for HOA boards and residents, not legal, tax, or financial advice. Rules vary by state and by your community's governing documents - check with a professional for your situation.

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