Iron chlorosis -- yellow leaves with green veins — print version.
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SUS Farms · Utah Gardening
Iron chlorosis -- yellow leaves with green veins
soil · intermediate · ~4 min read
The most-asked Utah garden question. Leaves turn yellow but the veins stay green -- that pattern almost always means iron deficiency, and almost always traces back to alkaline soil locking up iron the plant can't absorb. Iron supplements fix it temporarily; soil pH amendment fixes it for years.
How to spot it
Newest leaves turn pale yellow first. Veins remain dark green -- the signature pattern. In severe cases the entire leaf turns cream-white and curls. Most common on tomatoes, peppers, pin oak, river birch, maple, raspberries, and any acid-loving plant in our soil. Not the same as nitrogen deficiency, where ENTIRE leaves yellow including veins, starting with old leaves.
Emergency rescue: foliar iron
Iron chelate (Sequestrene 138, Ironite, Fertilome) sprayed on leaves at label rate. Greens up plants in 3-7 days. Best applied in early morning or evening -- leaves take it up faster when stomata are open. Repeat every 2-3 weeks through the growing season. This is a band-aid, not a cure.
Long-term fix: lower soil pH
Apply elemental sulfur in fall -- 1 lb per 100 sq ft for vegetable beds, 1 lb per inch of trunk diameter for trees. Work into the top 4 inches around the dripline. Soil bacteria slowly oxidize sulfur to sulfuric acid over 4-8 months. Re-test pH the following spring. Most Utah soils need repeat applications for 3-4 consecutive years to get below 7.0.
What does NOT work
Pouring vinegar on the soil -- burns roots, evaporates without changing pH meaningfully. Coffee grounds -- neutral by the time they decompose. Pine needles -- barely move pH. Aluminum sulfate -- works fast but toxic to soil biology long-term. Skip these and stick with elemental sulfur + foliar iron.
When to give up on a plant
If a tree has been chlorotic for 3+ years despite amendments, it's probably the wrong tree for the site. Pin oak, river birch, and red maple are the worst offenders in Utah -- better to remove and replace with hackberry, gambel oak, or chinkapin oak (alkaline-tolerant). Some plants just don't belong here, no matter how much iron you throw at them.