QUESTION: Why are my basil leaves turning yellow? I started with starter plants and not from seed this year, and the rest of the stuff in my garden seems to be doing ok. I can’t figure out what might be wrong. – Emily Y
JENNIFER POINDEXTER AT GARDENING CHANNEL REPLIES: There are multiple reasons why your basil leaves may be turning yellow. The first reason is the plant could be receiving too much water.
When a plant receives too much water, it leads to root rot. When the roots rot, no nutrients can be absorbed into the plant.
Therefore, it’s wise to practice the deep watering method. Water your basil plant deeply until water is running from the bottom of the container.
This should saturate the entire plant and allow excess to drain away. Test the soil by inserting your finger into the dirt next to the plant.
When the soil is dry to your first knuckle, it’s time to water the plant deeply again. If the soil is still damp, hold off on watering it and test the soil again in a few days.
Along with watering deeply, ensure you grow your basil in a container that allows for proper drainage.
Next, your leaves could be yellowing because your basil plant is receiving too little sunlight. Basil loves sun and should grow in a location where it gets six or more hours of direct sunlight each day.
Try moving your plant to a new growing location and see if this helps the color of the leaves.
Another reason the leaves of your basil plant could be yellowing is a lack of nutrients. Basil can grow in poor quality soil, but if the leaves are turning yellow for this reason, it needs a boost.
Apply an all-purpose fertilizer to the basil on a consistent basis. Follow the package instructions for guidance on application and frequency.
Cool temperatures can have a negative impact on basil plants. These plants enjoy temperatures over 70-degrees Fahrenheit during the day and above 50- degrees Fahrenheit at night.
If the temperatures dip below these ranges in the day or night, it could cause the leaves of your basil plant to become discolored.
The final reason your basil leaves could be yellowing is due to pests or diseases. Basil does have a common issue with fungal diseases. If you spot a fungal issue, be sure to treat it with a fungicide.
You can deter many fungal problems by planting in full sunlight, well-draining soil, and watering earlier in the day to ensure the foliage has time to dry before the cool night air moves in.
Pests also cause basil leaves to turn yellow. Aphids are a common issue for this plant. They feed on the plants which leads to discoloration of the foliage.
Should you spot an aphid infestation, be sure to spray the plant with soapy water or treat with an insecticide.
These are the most common reasons why basil plants develop yellow leaves. Remain alert to these issues to protect your plants.
Should you discover any of the issues listed here, be sure to correct them immediately. This will increase the likelihood of the basil plant making a full recovery and producing a delicious harvest.
Basil Quick Reference Growing Chart
| Stage | Details |
|---|---|
| Preparation | Soil pH: 6.0-7.5, Fertilize: 5-10-5 (3 oz/10 ft.), Varieties: Sweet, Spicy Globe, Lettuce Leaf, Lemon, Opal, Cinnamon, Thai |
| Planting | Sow after last frost, 1/4″ depth, Soil: Moist, Weed-free, Germination: 5-7 days, Thin to 6-12″ spacing, Mulch applied |
| Maintenance | Water: every 7-10 days (more for containers), Regular pruning, Prevent flowering for better yield |
| Harvesting | Snip young leaves as needed, Cut stems above leaf pair for regrowth, Fresh is best |
| Preservation | Air-dry or freeze leaves, Store in airtight container, Use frozen within a year |
| Pest Management | Monitor for pests, diseases, and disorders. Basil downy mildew is common. Seek professional help for diagnosis and treatment. |
More About Basil
https://hgic.clemson.edu/factsheet/basil/
https://extension.umn.edu/vegetables/growing-basil
https://plantvillage.psu.edu/topics/basil/infos
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