Why Are My Plants’ Leaves Turning Yellow?

An ever-so-common question asked in the gardener community is: “Why are my plants’ turning yellow?!” 

There is not a one-size-fits-all answer–as there are many environmental factors at play that impact your garden’s health. However, if you know how to read the clues your plant gives you, you’ll be able to identify why your once-beautiful leaves have lost their luster. 

What Is Chlorosis?

While some symptoms of plant disease are challenging to spot, chlorosis makes itself known to even the most novice of gardeners. Chlorosis refers to normally green plant tissue that is pale, bleached, or yellow.

Oftentimes, chlorosis only affects the tissue between plant veins (also known as interveinal chlorosis)–resulting in green veins and pale-colored leaf material elsewhere. Plants suffering from severe chlorosis exhibit stunted growth and dead shoots. 

This yellowing occurs when chlorophyll fails to develop–which is responsible for plants’ green color and is necessary for the plant to produce the food it needs to grow.[1] Chlorosis is not just an aesthetic issue. It’s indicative of a struggle for vital growth functions. 

Why Are My Plants Yellow?

While the list of symptoms of chlorosis is short, the same cannot be said of the causes. The potential causes of leaf chlorosis can be due to an array of chemical or physical issues.[2] Some of the most common causes are due to: 

• Nutritional problems

• Viruses

• Water-related issues

• Pests

Soil Nutrients and Yellow Plant Leaves 

As to be expected, different nutritional deficiencies manifest in different ways. While the best way to pinpoint the exact nutrition-related problem is to test your soil, there are a few trademark symptoms for specific nutrient deficiency. 

Below is a list of typical symptoms and remedies for a common nutrient issues:[3]

Potassium Deficiency:

• Symptom: Yellowing of leaf edges and tips.
• Solution: Add compost rich in fruit or vegetable rinds.
  
  

Magnesium Deficiency:

• Symptom: White or pale-yellow stripes along leaf veins.
• Solution: Add epsom salts or lime to soil.
  
  

Calcium Deficiency:

• Symptom: Misshapen, yellow leaves.
• Solution: If soil is alkaline, use gypsum. If soil is acidic, add lime to your soil. Read more about soil pH here.
  
  

Zinc Deficiency:

• Symptom: Discoloration between large leaf veins.
• Solution: Spray with kelp extract.
  
  

Iron Deficiency:

• Symptom: Leaves turn yellow with small green veins.
• Solution: Test pH and if it is high, lower to below 7.0. Iron becomes more soluble as pH lowers.[4]  Be sure to avoid copper or phosphorus-containing fertilizers–as excess phosphorus can tie up iron in the soil and make it unavailable to plants. 

If any of these nutrient deficiencies becomes severe, chlorotic tissue can turn brown. 

Nutrient toxicity can also present as chlorosis because excess nutrients in soil often displace or inhibit the uptake of other nutrients.[5]

Water-Related Issues and Yellow Plant Leaves

Maintaining the proper water content is a balancing act when it comes to staving off chlorosis. 

Leaf yellowing may occur both when: 

• Soil is too compact and/or becomes persistently waterlogged
• Soil experiences persistent drought conditions

If either of these instances persist, plants often lose their leaves entirely. The best way to fix water-related issues (besides adjusting your watering schedule): alter soil texture through the addition of sand to improve drainage. 

Temperature also plays a role in leaf pigment. Chlorosis can be brought on by cooler temperatures and often presents during the spring time in young plants.[6] A good tip to help you stabilize your soil temperature: apply a one to two inch layer of organic compost, followed by three to four inches of organic mulch. Along with creating favorable conditions for root growth, this combination will prevent soil temperature fluctuations during both winter and summer. 

Viruses and Yellow Plant Leaves

Viral infection in plants most commonly results in some varying degree of chlorosis.[7] While it is unlikely that a virus would cause uniform yellowing across the leaves–patterns such as mosaics, streaks, or ringspots are a telltale sign of a viral infection. 

Note: symptoms of viral infection in plants are highly variable–and depend on factors such as host plant variety, strain of virus(es), and weather conditions. 

Pests or Diseases and Yellow Plant Leaves

Non-viral disease can also cause leaves to turn pale or yellow. Spot diseases, mildews, and rusts can all result in chlorosis for various reasons.[8],[9] If any of these diseases are the cause, you can often confirm by spotting fungal growth on or near yellowed areas. 

Additionally, pests that attack plant roots or foliage often also cause leaf yellowing. Aphids, whiteflies, and red spider mites can all be possible culprits. 

Questions About Your Soil’s Health? 

If you have questions about soil health or testing, send us a message at hello@gosimplelab.com and our team of engineers, scientists and environmental experts will be happy to help.