Iron Deficiency

Chlorosis, or the yellowing of plant leaves, can have several different causes, one of which is an iron deficiency.

An iron deficiency is easy to identify because it begins with the yellowing of leaves while the veins stay green. This usually starts on new leaves. If left untreated, the leaves will turn lighter, including the veins and brown spots/edges may appear. I've seen some so deficient that the leaves have turned white and almost look scorched. Once this extreme is reached, the plant will begin dropping leaves.

Iron plays a vital role in chlorophyll production, which is essential for the plant to make food through photosynthesis. 

Iron deficiencies are common in alkaline (pH above 7.0) soils. When the pH is high, the iron gets "locked up" in the soil and cannot be easily absorbed by plants. The plants that struggle most usually prefer a lower pH (acidic soil) where iron is more abundant and more easily taken in.

How do we "unlock" the iron that's already there? 

We need to lower the pH. 

Add organic material like compost, peat moss (not sustainable), pine needles (neutralize quickly during decomposition), Oak leaves (neutralize quickly during decomposition), and coffee grounds (great for soil, but are not effective long-term). Adding sulfur to your soil works, too. Follow instructions to avoid damaging plants, though. You can also use fertilizers specifically made for acid-loving plants.

Alternatively, 

you can quickly treat an iron deficiency by fertilizing with liquid iron in the form of iron sulfate or chelated iron. These work more rapidly by providing a form of easily absorbed iron. These products can be beneficial in high-pH soils and when dealing with severe deficiencies. However, consider these a quick fix rather than a long-term solution.

Fun Facts:

Pansies are known as an iron-inefficient species, which means they are prone to iron deficiency in soils with a higher pH. 

Marigolds are known as iron-efficient plants, meaning they can take up too much iron in soils with a lower pH, which can lead to iron toxicity.