Treatment Plans
Correct iron deficiency
Why are your plant's young leaves turning yellow while the veins stay green?
Iron is vital for your plants. It is an essential component of chlorophyll, the pigment that gives leaves their green color and captures solar energy. Without enough iron, chlorophyll production slows and then stops. This is called iron chlorosis.
Most often, the problem is not too little iron in the potting mix, but the plant's inability to absorb it. Excessively high pH (above 6.5) in the growing medium is the most common cause. In alkaline soil, iron becomes insoluble, like a rusty padlock whose key will no longer turn. Roots simply cannot take it up, even when it is abundant.
The effect is highly visible and specific. Iron deficiency always affects new leaves first. The leaf blade (the leaf's surface) becomes distinctly yellow while veins remain strongly green, creating a striking contrast. Left untreated, leaves may become almost white before dying and falling, considerably weakening the plant.
What to do now
- Choose an iron chelate for maximum absorption. EDDHA or DTPA forms are most effective because they remain stable and available even in high-pH soil.
- Prepare a watering solution. Dilute 1 to 2 grams (about 0.035–0.071 oz) of powdered iron chelate per liter (about 1.06 US qt) of water. Follow the package doses carefully.
- Water generously with this solution. Soak the entire root ball so all roots can benefit.
- For a quick boost, spray the same solution directly onto foliage. Leaves absorb iron faster, offering visible improvement within a few days. Avoid doing this in full sun.
- Address the root cause: if your potting mix's pH is too high (often because of very hard irrigation water), consider using rainwater or filtered water.
Prevention
- Use potting mix with a slightly acidic pH (5.5 to 6.5) suited to your plant.
- Prefer rainwater or demineralized water if your tap water is very hard.
- Feed once a month during spring and summer active growth, where applicable locally, with a complete fertilizer containing trace elements including iron.
- Ensure good pot drainage to prevent root suffocation, which limits nutrient absorption.
Common problems
- Soil pH too high · Soil blocks the plant's access to essential nutrients.
- Iron deficiency · Young leaves turn yellow while their veins stay green.
FAQ
What is the difference between iron and magnesium deficiency?
The main difference is where symptoms appear. **Iron** deficiency (iron chlorosis) affects **young leaves** and new shoots first. **Magnesium** deficiency appears on the **oldest leaves**, often as V-shaped yellowing or yellowing at the edges, while veins remain green.
What is chelated iron, and why is it more effective?
Chelated iron is iron 'protected' by an organic molecule (a chelating agent). This prevents chemical reactions in high-pH soil that would make it insoluble. The chelate keeps iron **available and absorbable** by roots, even in unfavorable soil conditions.
How soon will I see an improvement?
With foliar spraying, young leaves may become greener within **a few days to a week**. Soil application gives slower but longer-lasting results: expect visible improvement within **2 to 3 weeks**, while roots absorb iron and distribute it to new growth.
Can I put rusty nails in the pot to supply iron?
No. This widespread gardening myth is ineffective. Rust is iron oxide, a **chemically insoluble** form that plant roots cannot absorb at all. Even in soil full of nails, the plant will remain deficient. Always use chelated iron, specifically designed to be absorbable.
What can make my potting mix's pH too high?
The most common cause is repeated watering with **very hard tap water**. Limescale accumulates over time and raises the growing medium's pH. Some poor-quality potting mixes may also start with an overly alkaline pH.
Which houseplants are most susceptible to iron deficiency?
All acid-loving plants are particularly vulnerable. Indoors, watch **gardenias**, **calatheas**, **potted citrus**, **azaleas** and **ferns** carefully. They are the first to show chlorosis when soil pH is unsuitable.
What is the difference between EDDHA, DTPA and EDTA chelates?
They differ in stability at different pH levels. **EDTA** works in acidic to neutral soils (up to pH 6.5). **DTPA** is stable up to pH 7.5. **EDDHA** is the most effective and stable, remaining effective in very alkaline soils (up to pH 9 and above). For houseplants whose soil pH tends to rise because of watering, EDDHA is often the safest choice.