Why are the newest leaves on my plant coming in yellow while the older leaves look normal?
Interveinal chlorosis appearing first on new growth points to iron deficiency — most often caused by high soil pH locking iron out of root uptake rather than iron being absent from the soil.
Iron deficiency presents as pale yellow or almost white tissue between the veins on the youngest, most recently emerged leaves. Unlike magnesium deficiency, which starts at the bottom of the plant, iron deficiency shows at the growing tips and newest leaves first. The veins remain green against the yellowed tissue, giving a net-like appearance. In severe cases the entire young leaf turns nearly white. Older leaves lower on the plant may look healthy at the same time the new growth looks washed out.
Iron is immobile in the plant — it can't be relocated from old tissue to new growth the way mobile nutrients like magnesium can. So a shortage shows up immediately in whatever tissue is actively forming. The most common cause is not a lack of iron in the soil but soil pH above 7.0, where iron becomes chemically unavailable even when it's physically present. Waterlogged or compacted soils limit oxygen, which also impairs iron uptake. Blueberries, azaleas, and raspberries — all acid-loving plants — are especially prone in neutral or alkaline soils.
The first step is a soil pH test, not an iron amendment. If pH is above 6.5 for most vegetables (or above 5.5 for acid-loving plants), lowering the pH is the real fix. Sulfur or acidifying fertilizers lower pH gradually over weeks to months. For a faster short-term response, chelated iron — available as a granule or liquid drench — stays available to plants across a wider pH range than standard iron sulfate. Foliar chelated-iron sprays can green up leaves noticeably within a week. Do not apply standard iron sulfate to high-pH soil without also addressing the pH; the iron will lock up again quickly.
If pH is already in range and deficiency persists, check drainage. Roots sitting in saturated soil can't take up iron effectively regardless of soil chemistry. Improving drainage or reducing irrigation frequency often resolves the issue without any amendments. New growth coming in at normal color after treatment is a reliable sign the problem is corrected; leaves that were yellow when iron was deficient rarely green up fully, so look to the new leaves as your progress indicator.
- BlueberryAn acid-soil shrub that demands a pH most gardens don't have — and cross-pollination from a second variety you'll need to plant next to it.
- RaspberryA perennial cane that fruits on last year's wood or this year's, depending on which kind you plant.
- TomatoThe warm-season anchor of the summer garden.
- PepperA tropical perennial grown as an annual — patient, slow, and particular about warmth.
- AphidSoft, clustered insects on new growth causing curled leaves and sticky honeydew.
- Bird DamageBerries pecked or missing, seeds scratched from beds, and seedlings dislodged — birds feeding on ripe fruit, seeds, or soil grubs.
- Black RotV-shaped yellow lesions at brassica leaf margins with blackened veins inside — a bacterial disease that moves through the vascular system.
- Blossom End RotDark, sunken, leathery patch on the blossom end of tomato or pepper fruit — a calcium deficiency disorder.
- Brown Marmorated Stink BugSunken, corky dimples on fruit and pods caused by a mottled brown shield bug feeding through the skin.
- Why are the leaves on my tomatoes or peppers yellowing between the veins while the veins stay green?Interveinal chlorosis on older, lower leaves is a classic sign of magnesium deficiency — the plant is pulling magnesium from mature tissue to feed new growth.
- Why do my seedlings or young plants have purple or reddish undersides on their leaves?Purple or red coloration on leaf undersides and stems is a common sign of phosphorus deficiency, and cold soil in early spring is often the trigger even when phosphorus is present.
- My soil pH is too high (alkaline) — what can I do about it?Sulfur is the standard amendment for lowering soil pH, but it works slowly — expect 6–12 months for meaningful change, and retest before planting rather than adding more based on symptoms alone.
- When and how should I adjust my soil pH, and how long does it take to work?pH amendments work slowly — sulfur and lime both take weeks to months to shift pH — so the most effective time to apply them is in fall or at least 6–8 weeks before planting, not at planting time.