Iron Deficiency in Trees and Shrubs: Chlorosis Explained

Just like people, trees and shrubs need a variety of micronutrients to grow strong and healthy. One of the most important is iron. This metal plays a critical role in the synthesis of chlorophyll, the green pigment that enables plants to “eat” by converting sunlight into energy. Without sufficient iron, trees and shrubs can develop iron chlorosis or yellowing of the leaves, which means they can’t get all the nutrients they need to thrive. Needless to say, ensuring your soil has enough iron is an essential part of growing (and maintaining) a thriving outdoor living space. 

Since plants absorb iron from the soil, it’d be reasonable to assume that chlorosis occurs when your soil lacks sufficient iron. However, that’s not always the case. Iron is one of the most abundant elements in the Earth’s crust, and it’s almost certainly abundant in your soil. The problem, at least where your plants are concerned, is that it can be difficult for plants to access. Iron binds tightly to other minerals in the soil, limiting its ability to be absorbed by your plants’ roots. It’s an especially common problem for those with high-pH soils, as the alkalinity significantly diminishes the iron’s solubility. If your plants aren’t equipped to adapt to these conditions, iron deficiency — otherwise known as iron chlorosis — will result.

Overwatering can produce symptoms that appear similar to an iron deficiency.  Plants can become yellow or chlorotic from the lack of oxygen around the roots, and from the loss of nitrogen by leaching (or draining away from the soil).  An overwatered plant will also struggle to take up iron from the soil, compounding the problem.  Soil compaction, topsoil erosion and poor soil drainage — as well as anything that limits oxygen to the roots – will reduce iron uptake. Finally, cool soil temperatures can cause or worsen iron chlorosis (in these cases, the deficiency will usually improve once temperatures rise).

If you’re concerned about chlorosis, there are a few iron deficiency symptoms in plants to look out for. Signs of iron deficiency in plants include: 

• Chlorotic leaves at the tip of the blade (yellowing of the leaves due to a lack of chlorophyll)
• Darkening of the leaf veins (interveinal chlorosis)
• Slow or stunted growth
• Scorching or browning of leaf edges

Because these symptoms aren’t exclusive to iron chlorosis (leaf discoloration, for example, can be caused by disease), you’ll want to rule out other possible causes before treating your plants for iron deficiency. Your local TruGreen expert can help with this by assessing your trees and shrubs to determine the root cause of your concerns.

Since iron chlorosis is a direct response to what’s going on in your soil, the best way to prevent it is to take care of your soil. Trees and shrubs planted in alkaline soils are more susceptible to iron chlorosis, so testing your soil’s pH can help determine if that is the cause. Adhering to a proper watering schedule may help to prevent iron chlorosis, as well. If you’re not sure how often to water your trees and shrubs, ask your TruGreen specialist. They’ll work with you to determine the ideal watering schedule for your property (and can also arm you with tips and tricks for keeping your plants in optimal health).