Yellowing leaves will be the biggest indication that your houseplants are suffering and is often misunderstood. When noticing yellowing, many plant parents will jump to water or give their plant a heavy dose of liquid feed.
However, this can make the problem worse.
Chlorosis is a condition where the lack of chlorophyll production causes the leaves to lose their natural green colour. The reason chlorosis occurs isn’t just because plants need more food! It is a complicated chemical reaction meaning your plant is suffering from imbalance in nutrition, pH or toxicity within the root zone. To resolve this issue we need to stop guessing, and understand how nutrients are transported around the plant.
Mobile and Immobile Nutrients
To understand what nutrient deficiency your plant has, we need to look at where the yellowing is appearing. Different elements are translocated depending on their mobility within the phloem.
If your plant is suffering from a lack of mobile nutrients (N, P, Mg, K) then these will be translocated from older lower leaves, to provide the new growth. This means mobile nutrient deficiencies will show yellowing from the bottom leaves.
Immobile nutrients (Ca, Fe, S, B) won’t be able to be moved from where they have been placed. If the root zone doesn’t have enough iron or if the soil is too alkaline then the plant won’t be able to provide the developing leaves. This means immobile nutrient deficiencies will show yellowing from the youngest leaves.
Confusing the lack of iron in new growth with a lack of nitrogen in old growth will cause overfeeding. Adding extra nitrogen to a plant that is already struggling with iron uptake will cause salt levels in the soil to increase. This will increase the electrical conductivity and burn the roots.
Reasons for Nutrient Lock Out
Sometimes the plant food in the potting medium won’t be absorbed by the roots. This can happen because:
Roots won’t get oxygen due to wet soil. If there is too much water in the soil then the root cells won’t be able to respire. This will prevent active transport of mineral ions through the cell membranes. Your plant will show nitrogen chlorosis even though there is plenty of nitrogen in the soil.
pH of the medium. Most tropical houseplants prefer slightly acidic mediums between 5.8 - 6.5. Over time tap water minerals will cause the pH to increase. This causes lock out as iron and other essential micro nutrients will combine chemically with the soil.
Low light. If your plant is in a dark spot it won’t be using as much nutrients as a plant in bright indirect light. Adding food to a plant that is not getting enough light will cause mineral salts to build up. This will cause damage to the roots and brown tips on the leaves.
How To Fix Chlorotic Plants
To fix your chlorotic plant, you’ll want to keep track of what’s going on. Modern plant care now involves keeping track of trends to see what is causing your plant to suffer.
Keeping track of when you watered, how much light and when you fed will show you how changes in the climate are affecting your plant. Keeping track of the environment will allow you to change the strength of your feed during seasons of dormancy. If you’re looking for a way to remove the guess work from your plants, there are specialist platforms that offer data driven plant care and diagnostic tools to help you keep your plant’s nutrients at the optimum.
3 Ways to Safely Fix Chlorosis
Rather than guess what your plant needs, follow this checklist:
Where is it happening? Are your plant showing chlorosis on old leaves or new leaves? This will tell you if it’s a mobile or immobile element.
Rinse your substrate. If you think there is a build up of mineral salts then rinse your potting mix thoroughly with distilled or reverse osmosis water.
Only feed when growing. Only add diluted feed when your plant is actively growing and has enough light to utilise the nutrients.
By paying close attention to how your plant is reacting you’ll be able to fix any yellowing leaves. This will create a strong indoor jungle!
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