Iron and Proteas: What You Need to Know

Iron Sulfate

Proteas are acid-loving plants, and keeping them healthy depends on getting the soil pH right. Iron is essential for green, healthy leaves, but in alkaline soils, iron becomes locked up and the plant’s roots can’t take it in. This often shows up as yellowing leaves, a problem called iron chlorosis.

Check Your Soil First

Before adding any iron, it’s important to know your starting pH. A soil test will tell you where things stand and help you choose the right fertilizer and dosage.

• DIY kits – Quick, easy, and color-coded.

• Digital meters – Instant and more precise - but you get what you pay for.

• Professional labs – The most accurate option; includes nutrient analysis for a tailored plan. Your local county extension office may have some referrals.

  
  

Goal: Adjust the soil to a pH between 5.5 and 6.0, the sweet spot for iron uptake.

Adjusting Soil pH

A simple way to lower pH is with granulated sulfur. Soil microbes gradually convert it into sulfuric acid over a few weeks, slowly shifting the soil into the acidic range. This creates a favorable environment where nutrients, especially iron, can be absorbed efficiently.

Tip: Knowing your starting pH is crucial to applying the correct amount of sulfur. Too much at once can cause problems.

Iron Sulfate: Quick Fix

Iron sulfate (FeSO₄) is a traditional fertilizer that works fast. It can quickly green up leaves in acidic soils and is an inexpensive option.

However, there are some downsides:

• It doesn’t work so well in alkaline soils.

• Over application can burn roots, which is risky for sensitive plants like proteas.

• It can stain hard surfaces.

DTPA Iron Chelate

Iron Chelates: Long-Term Solution

Chelated iron stays available to plants longer. A chelate wraps the iron in an organic molecule, preventing it from locking up in the soil. Chelates are best applied only as a soil drench. I've had issues with leaf burn in the past so I'm always a little cautious applying it as a foliar spray.

• Fe-EDTA – Works in soils below pH 6.5. Affordable and suitable for acidic soils.

• Fe-DTPA – Stable up to pH 7.5. Good for slightly alkaline soils.

• Fe-EDDHA – The most stable and most expensive. Works in soils up to pH 9.0, perfect for stubborn chlorosis.

Key Takeaways

1. Test your soil before adding any iron - I know I'm repeating myself but this is important.

2. Adjust soil pH to 5.5–6.0 using granulated sulfur. Takes some time work.

3. Use iron chelates only as a soil drench (not a foliage spray), and choose the type that matches your soil pH.

Iron and Proteas - when done right, your plants will reward you with deep green leaves, strong growth, and beautiful flowers. The first step—getting the pH right—is the most important part of the process - after a soil test - ok, I'll stop now.