Parsley leaves can yellow because of root rot (most commonly) due to wet soil or as a result of lack of water.
They can also yellow as a result of chewing from aphids or spider mites.
Yellow leaves don’t have to mean bad news. If sickness is the culprit, it would be best to discard the contaminated yellow parsley.
If pests or some other causes are the problems, you can eat the leaves if you‘d like. They may not have the same flavors as greener leaves, but it isn’t necessarily bad.
Causes of Yellow Parsley and the Control Measures
| Causes of Yellowing Parsley | Control Measures |
|---|---|
| Viral/fungal/bacterial | Exclusion, eradication, protection |
| Water | Don’t underwater or overwater |
| Compacted root damage | Incorporate organic materials/mulch |
| Light | Ensure the plant receives enough sunlight |
| Soil PH | 6.0-7.0 |
| Nutrients | Use a lot of compost |
| Pests | Use predatory insects to control |
How to Identify Parsley That Has Turned Yellow Due To Diseases
Leaf spot disorders are caused by three classes of pathogen:
- Fungi,
- Bacteria,
- And virus.
The diseases mostly yellow the plant, but usually only small brown spots outlined in yellow instead of total yellowing of their colors.
Have you ever seen:
- Viral disease signs: Yellowed leaves, mosaic leaf patterns, plant stunting, crinkled leaves.
- Fungal disease signs: Damping-off of seedlings, yellowed leaves, leaf spot.
- Bacterial disease signs: Bacterial leaf spots on the upper and lower surfaces of the leaf; blight-like symptoms of total collapse; and small black fruiting bodies of the fungus.
Prevention methods:
- Exclusion: This prevention method involves all measures to prevent the introduction into a farm of a disease-causing agent (pathogen).
- Eradication: This prevention method is based on eradicating a disease that has already entered the farm before it becomes established or widely disseminated. Farming practices that help with eradication are crop rotation and soil fumigation.
- Protection: This prevention method uses a physical barrier between the plant and the pathogen. Protection can include fungicides, irrigation, and adjusting the soils PH.
How to Identify Other Causes of Parsley Turning Yellow
Lack of Enough Water or Too Much Water
Moisture stress is one of the top reasons parsley leaves turn yellow.
If your parsley plant is not getting enough water, the leaves are going to start drooping in an effort to avoid excessive transpiration.
Leaves might curl inwards, sag down, or go crunchy. All of these means your plant is not getting adequate water.
Conversely, if a plant is getting too much water, it can mean fading leaves.
When soil can’t drain well, it gets heavy and saturated.
The roots are going to drown, and so there is little to no oxygen.
Treatment: Don’t underwater or overwater your parsley.
Compacted Root Damage
Roots can be damaged in many ways, from really bad shovels to rot.
When roots are damaged they may not be able to supply the plant with the water, oxygen and nutrients they need, and may behave in a manner that gave you yellow leaves. This is where the roots can no longer function properly.
Compacted root rot damage.
Treatment: To keep your parsley leaves green; add organic materials, and organic mulch to your planting areas.
Too Little Light
Inspect the leaves closely.
A parsley plant that is not receiving enough light will turn yellow on the opposite side of the light source.
The edges of the plant closest to the light may be blocking the sun.
Treatment: Move the plant somewhere sunnier, or put up an artificial light.
Improper Soil PH
Soil pH affects plant nutrient availability.
The availability of nutrients changes across the soil pH scale. For example, parsley prefers growing in soil with a PH about 6 to 7.
If the soil pH goes below or above optimal nutrient range, some nutrients will become less available to wayward .
Even with added, fertilized nutrients in the soil, nutrients will not be absorbed. Soon to follow, leaves turn yellow.
Treatment; do something about the PH problem.
Nutrient Deficiency
The top leaves are going to start yellowing before the old leaves, and may develop a weird pattern on top of the yellowing.
They can develop black veins, or the yellow tissue could develop between the veins. Or, it will grow slowly.
Treatment: For nutrients, you will want to add a lot of compost.
Pests
Pests of parsley plants are aphids and spider mites. They produce small yellow spots on the parsley leaves.
Treatment: Use predatory insects to combat these pests.
Final Thoughts
There is an assortment of pathways to why parsley leaves are turning yellow.
Some have their basis in disease, lack of water or too much water, roots become compact, rot damage, light limitation, incorrect soil PH, nutrient deficiency, and pests.
It is paramount to figure out the specific cause of why the parsley leaves become yellow as this determins if the yellow leaves can be safely eaten.