By Bev Johnson

Master Gardener

Iron is only one of 16 essential elements that plants need to grow. Here are the others.

Macronutrients. Nitrogen (N), Phosphorus (P), Potassium (K), Carbon (C), Hydrogen (H), and Oxygen (O). then there are the secondary nutrients. Calcium (C), Sulfur (S), and Magnesium (MG).  and micronutrients. Iron (FE), Manganese (Mn), Molybdenum (Mo), Chlorine (Cl), Boron (B), Copper (Cu) and Zinc (Zn). As you can guess, macronutrients are needed in the biggest quantity and micronutrients in the smallest.

A healthy soil will contain all these elements from molecules obtained from the air (Oxygen and carbon dioxide gasses, and as ions, electrically charged particles dissolved in water in the soil. If even one of these essential elements is lacking, your plant will not do well and probably die.

Iron deficiency symptoms can appear quicky because iron is involved with chlorophyl and photosynthesis. Let’s get scientific now. A plant must have iron for the synthesis of chlorophyll and chloroplasts, the structure chlorophyll is housed in. It is not in the chlorophyll itself. As we all know, chlorophyll is what makes leaves green. Simply put, lack of iron turns leaves yellow and yellow leaves can’t properly feed the plant. This yellowing is called cirrhosis. It can be caused by other things but suspect iron deficiency first. A telling symptom is yellow leaves with green veins. Nitrogen deficiency will make the whole leaf yellow. Iron deficiency shows up in new growth first. Iron is relatively immobile in plant tissue and can’t be easily absorbed from older tissue and sent to the new growth unlike nitrogen and manganese. Manganese deficiency shows up in older foliage first. 

If the lack of iron continues, the yellowing will be just here and there at first, affecting some stems and not others. Eventually, new growth can become white, smaller than normal and then die.

Iron can become unavailable to plants if the soil is too alkaline, high in copper, manganese, or zinc, or waterlogged. No plant does well in waterlogged soil. Soil in Otter Tail County is slightly alkaline. Most essential elements are more soluble in water and available to plants as the alkalinity decreases and becomes more acidic. A soil test will tell you if this is your problem. Now, how do you solve this problem?

To start with, don’t plant acid-loving plants like blueberries, azaleas, rhododendrons, river birch and pin oaks. Petunias and bacopa also like a more acid soil although they will tolerate ours.  Adding elemental sulfur to the soil will acidify it. Sulfur will allow the iron to be available to the plants. This is not a quick solution as it will take several months to do its thing and is more of a long-term solution. For a more short-term solution, you will need chelated forms of iron to slow continued injury. This is often chelated iron with EDTA (ethylenediamine tetra-acidic acid) added. This can be a foliar spray or a liquid to add to the soil. You should see the results in a few weeks. We probably see more of this problem than usual if our soils become wetter than usual.   

You know it’s hot when you see squirrel laying all sprawled out on your deck rail or on a tree branch. Even if you don’t like the little critters, be nice and leave a pan of water for them and the birds. Birds like a shallow bowl so they can bathe. They also leave a messy bathroom with water with feathers floating in it. They like to poop in their bath too. Do clean it up as they don’t have opposable thumbs. They also need drinking water, but that bowl should be deeper to deter bathing.