Why Is My Lemongrass Leaves Turning Yellow?

Are your lemongrass leaves turning yellow?

The lemongrass leaves may turn yellow due to lack of water, specific nutrients, or fungal disease infection. In addition, the leaves may turn yellow during the winter extremes due to a lack of exposure to sunlight.

Keep reading to find a detailed explanation of why your lemongrass leaves may turn yellow and how you can help the plant regain its green color.

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Your lemongrass leaves may turn yellow due to:

Fungal Diseases

  • Researchers claim that more than 19,000 pathogenic fungi can negatively impact your plants (including the lemongrass).
  • Pathogenic fungi produce spores,  which are transferred to the lemongrass leaves by wind,  insects, water, humans, and even garden equipment.
  • Upon landing,  they may start infecting the plant or stay on the leaves until the conditions become favorable for them to develop.
  • The necessary conditions for the growth and spread of the fungal spores are adequate air temperature and moisture.
  • And the common sign of fungal infestation in lemongrass plants is the yellowing of leaves.
  • Examples of the common fungal diseases that may cause the yellowing of your lemongrass plant  include:

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1. Rusts

  • The fungal rust causes raised spots called pustules on the lemongrass leaf surface.
  • You can identify the rust pustules by their blend of bright yellow, reddish-brown, orange-red, and black-colored spots on the lemongrass leaf surface.

2. Powdery Mildew

  • This is a  superficial fungal infection that is caused by different fungal species in the order Erysiphales.
  • You can identify it by the presence of light gray or white or light gray powdery spots on the lemongrass leaves. If left untreated,  the affected leaves may become yellow, wither and die.

3. Downy Mildew

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  • Downy mildew is common in plants growing in cool and humid regions. It is caused by different species of fungus of phylum Oomycota.
  • You can identify a downy mildew infection by pale yellow and greenish-yellow patterns on the lemon grass leaf surface.
  • You can reduce fungal infections in your lemongrass plants by:
    • Spraying fungicides: To kill and counter the growth of the spores
    • Pruning infected leaves:  To avoid spreading the spores further
    • Avoiding overhead irrigation:  This will deny the fungal spores  the moisture they need to grow on the leaves
    • Spacing the lemongrass plants: To reduce their likelihood of infecting each other

Also, Read: Why Is My Lemongrass Plant Dying? [11 Reasons & How to Prevent]

Poor Watering Practices and Poor Drainage

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  • Water maintains the lemongrass plant cell turgidity, giving it structure. It also supplies the plant with essential nutrients and organic compounds for growth and development.
  • But did you know too much or too little of it can be detrimental to your lemongrass plant?
  • If your lemongrass leaves are yellowing and you have excluded fungal infestation as one of the culprits,  then, perhaps,  you are overwatering or underwatering it.
  • Overly wet soil may suffocate the roots, making them unable to absorb nutrients that the lemongrass plant needs for development.
  • As a result,  the nutrient-deprived lemongrass plant leaves end up yellowing to signify a problem in its system.
  • On the other hand, underwatering your lemongrass plant may limit the number of nutrients the plant can absorb from the soil, resulting in yellow leaves.
  • So, what’s the best way to hydrate your lemongrass plant? Start by working on the soil drainage.
  • You can enhance the soil drainage by adding lots of organic matter to the soil.
  • For instance, you can mix your clayed soil with compost manure, grass clippings, shredded leaves, and farm manure, or blend the soil with several organic materials.
  • With good drainage, the soil will drain water well while retaining enough moisture and air for optimal operation of the plant roots and biological activity.
  • Another way to ensure that you don’t overwater or underwater your lemongrass plant is to water the soil when it feels dry.
  • You can achieve this by giving the soil a finger test before watering.

Also, check: Why Is My Lemongrass Turning Purple? [Reasons & How to Fix]

Poor Soil pH

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  • Another possible culprit behind the yellowing of your lemongrass leaves might be the wrong soil pH.
  • A wrong soil pH interferes with the absorption of nutrients, and the resulting nutrient deficiency results in the yellowing of leaves.
  • The lemongrass plant, for instance, does excellent in nitrogen-rich soils with a pH of 5.5-7.5.
  • If you live in California, where the soil pH can go below or beyond this range,  you should test the soil pH to optimize it before you plant your lemongrass plants.
  • If the soil pH is too high, you should fertilize it with ammonium or urea-rich fertilizers to enhance the rate at which acid develops in the soil. 
  • Failure to lower the pH may interfere with the availability of phosphorus and other essential micro-nutrients.
  • On the other hand, too low pH may interfere with magnesium, calcium, and phosphorus availability.
  • It may also elevate the availability of manganese and aluminum compounds, which may be toxic to your lemongrass plant.
  • You can elevate the soil pH with lime to avoid yellowing your grass leaves.

Also, check: Are Coffee Grounds Good for Lemongrass?

Lack of Some Essential Nutrients

  • If your lemongrass leaves are yellowing and none of the above problems are the cause, your plant might lack some nutrients.
  • Suppose you suspect a nutrient deficiency in your yellowing lemongrass leaves.
  • In that case, it’s important to note that the leaves in different plants may exhibit different yellowing patterns depending on the lacking nutrients.
  • Below are some examples  to give you a clue of what we are talking about:

Lemongrass Stalks - 6 Plants

Nitrogen-Deficient Lemongrass Leaves

  • A nitrogen-deficient lemongrass plant looks pale to yellowish green.
  • The older leaves start yellowing from the inner parts and then spread outwardly. The plant experiences stunted growth during the period.

Magnesium-Deficient Lemongrass Leaves

  • When your lemongrass plant lacks magnesium,  the older leaves will start yellowing in the areas between the veins.
  • The veins retain their green color, and the yellowing spreads outward until it covers the leaf edges.

Sulfur-Deficient Lemongrass Leaves

The young leaves in your lemon grass plant start turning yellow throughout.

Potassium-Deficient Lemongrass Leaves

The older leaves in your lemongrass plant will turn yellow on the edges and later brown, while the inner part remains green.

Iron Deficient Lemongrass Leaves

  • Iron deficient lemongrass plant’s young leaves will turn yellow between the veins and then spread to older leaves.
  • You should familiarize yourself with signs that the lemongrass plants may exhibit when lacking certain nutrients to correct them when necessary.

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Also, check: Are Coffee Grounds Good for Hydrangeas?

Damaged or Compacted Root

  • Another possible cause of yellowing in your lemongrass leaves is damaged or compacted roots.
  • Compacted lemon grass roots are likely to happen if the plant has overgrown the container holding them, creating a mass of roots that occupy almost all space in the container.
  • When compacted, the lemongrass roots may not absorb water and nutrients well, resulting in the yellowing of the leaves.
  • Sometimes, the compacted roots may rot due to lack of oxygen and maybe, fungal infections.
  • With rotten roots, the plant may not absorb nutrients and has limited chances of survival.
  • However, you can transfer the plant to a larger container to allow for free growth of the roots.
  • Transferring the lemongrass plant will also allow for good drainage and better absorption of nutrients from the soil.

NOTES:

1. Transferring the lemongrass would only work if the plant has compacted roots that need extra space for growth.
2. A plant with completely rotten roots may not recover even after transferring. It’s essential to check the status of the roots before transferring your lemongrass plant to a larger pot or container.

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Poor Climatic Conditions

  • Typically, the lemongrass plant enters into dormancy when temperatures fall below 45°F. 
  • So, if you grow this plant in the Northern regions of the U.S., such as Indiana, where temperatures may dip down to 31°F, you should not be worried about seeing the plant leaves turn yellow from the cold weather and lack of exposure to sunlight.
  • However, since the temperature might be extremely low for the plant to survive,  you should cover it from frost and other elements lest you want it to die.
  • It is also advisable to keep the yellow and drooping leaves during winter,  as they help to protect the living cells from the external elements.
  • If you are used to trimming, please wait to do so during spring, when the temperatures become at least favorable for the lemongrass plant.
  • Remember to expose your lemongrass plants to the sun to help them regain their green color during spring.

Pest Attack

  • The lemongrass is known for being a pest and insect repellant plant.
  • However, the plant may experience the worst attacks from stubborn pests like the yellow sugarcane aphid which cause its leaves to turn yellow.
  • The mealybug is another example of a pest that may cause the yellowing of your lemongrass plant leaves. They are attracted to the lemongrass plant by its sweet citrus fragrance.
  • One way of identifying a mealybug attack in your plant is by looking for yellow spots and a waxy coating on the leaves.
  • You can control mealybugs using highly rated insecticides.
Why Is My Lemongrass Leaves Turning Yellow
Why Is My Lemongrass Leaves Turning Yellow

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Final Words:  Why Is My Lemongrass Leaves Turning Yellow?

  • Your lemongrass leaves may turn yellow due to lack of water, lack of nutrients, or due to other causes discussed in the article.
  • Luckily, there is something you can always do to help the plant regain its color provided that its roots aren’t completely rotten.
  • But, if you prefer preventing the yellowing rather than treating it, you should prioritize sufficient watering, good soil drainage, optimal soil pH, and fertility while ensuring sufficient space for the roots.
  • You should also provide sufficient spacing between the lemongrass plants to avoid the risk of the lemongrass plants infecting each other.