Iron chlorosis could very well be the most common plant problem I see here at the garden center. Simply put, Chlorosis is the technical term for leaves yellowing due to lack of chlorophyll, the compound that makes leaves green. And Iron Chlorosis is chlorosis caused by a lack of iron.
Photo credit to Utah State University
What causes a lack of iron? Like, many plant problems it starts in the soil. Southern Idaho soils can have plenty of iron in reality. The difficulty comes with the plant actually having access to it. The pH of the soil dictates what nutrients are and are not available to our plants. Here in Southern Idaho, our soil is alkaline (above 7). Many of us have soils in the 8 - 8.5 range. This makes iron very difficult to access, and turns our leaves yellow. The chart below shows how pH effects the availability of certain nutrients.
How can I fix it? Reversing iron chlorosis can be done in 2 methods. 1) Provide supplemental iron and 2) Lower your soil pH.
1) is pretty straight forward. This can be done by applying any chelated iron product. It can be applied to the soil or directly onto the plant. This will help give it the nutrients its missing. Foliar applications act quicker than soil applications but soil applications feed for a much longer period of time.
2) Lowering pH or acidifying can be done in any number of ways.
- Organic Matter: by adding mulch, compost and other organic matter, you introduce beneficial microbes to the soil that produce organic acids.
- Elemental sulfur: Sulfur, when interacting with water, creates sulfuric acid (in a non-harmful concentration) which lowers/acidifies your soil. ~1-2lb/100 sq.ft is an adequate application rate.
If you have any other questions feel free to reach out or comment! What issues would you like to see in the next Plant Problems? Let us know!