The leaves of thyme turn yellow as a result due to root rot excessive nitrogen, or not enough, or because of a spider mite infestation. Root decay is the most frequent reason behind thyme’s yellow leaves, which is the result of excessive moisture around the roots as a result of excessive watering or slow draining soils.
Thyme is prone to root rot since it is an Mediterranean herb that has a preference for dry soil and it is not tolerant of moist soil.
Thyme plants that have yellow leaves usually exhibit wilting or look of drooping, which is a indication of stress caused by humid conditions, excessive nitrogen, or even pot root ties.
Continue reading to find out the reason why your thyme is turning yellow, and the best way to fix the issue…
Thyme Turns Yellow (Over Watering and Slow Draining Soils)
The most frequent reason for the thyme plants to turn yellow is due to excessive soil moisture around the roots, which can be caused by:
- Too often watering thyme.
- Slowly draining soil.
Thyme is an Mediterranean plant that has adjusted to the harsh conditions of a sunny, dry climate that has a low frequency of rainfall. It thrives on sandy soils which are well draining and don’t hold water.
Due to thyme’s adaptation to dry climates, roots are not able to tolerate continuously humid soil.
The damp or moist soil around roots can cause the conditions that lead to the root to rot and is common for the thyme plant and other Mediterranean herbaceous plants like the lavender as well as rosemary.
The most common symptoms of a thyme plant that is suffering from root rot include:
- Brown or yellow leaves.
- A look that is wilting or droopy.
- Roots which have a dark-brown colour (rather than a lighter yellow hue).
A lot of moisture can cause fungal pathogens to flourish, which can cause the foliage to turn brown. For more information on how to revive thyme’s brown foliage it is recommended to read my article Why is my plant’s thyme becoming brown?
How do you solve it…
The most important thing to do in stopping and treating root rot that turns the leaves of your thyme in yellow, is:
- The thyme should be watered only once per week during dry weather, or every two weeks if there is a chance of rain. In the majority of cases, watering thyme every week, with an adequate soak is the ideal amount of watering for containers, pots. For garden soil, thyme is likely to not require watering in all climates since it is drought-resistant and can get sufficient moisture from the soil. The frequency of watering for thyme will depend on the climate you live in, so you should adjust the frequency of watering to ensure your soil surrounding your thyme plants appears dry to about the point of a finger before every watering session to ensure that the roots are healthy.
- Add sand or grit for better drainage. By adding grit or sand to the potter’s mix or the planting area mimics the conditions of sandy soils in the thyme’s natural Mediterranean environment. Sand ensures drainage and a proper nutrition balance, to ensure that the soil around the thyme is dry between waterings to avoid root rot.
- If your leaves are notably yellow and you’ve had to water your thyme way too often, it is essential to cut back any foliage that is yellow back in healthy development. Remove the thyme carefully from the ground and examine the roots. Cut off the dark, decayed or damaged roots and restore them to healthy growth. Clean the blades of your pruners using a cloth that has been soaked in disinfectant before each cut to avoid spreading the disease. Transfer the thyme into containers or pots with a new soil mix of 30 percent sand or grit, with 70% organic compost, provide the soil with a thorough soak to ease transplant shock and then place it in the sunlight.
Follow these steps to give thyme the best chance of healing within a couple of weeks.
If your thyme is suffering from decayed roots, I suggest to throw it away and burning the plant to stop the spread of fungal pathogens that could be found in your garden.
Prevention is more effective than cure by root rot, so purchasing an entirely new plant and putting the plant in pots that has the correct soil mix and properly watered is usually the best option.
If you have any other issues with your thyme plant , read my article on on how to revive the dying Thyme plant.
Too Much Nitrogen Turns Thyme Leaves Yellow
Your thyme plant may be yellow due to both an excess and a deficiency of nitrogen that is present in soil. An excess of Nitrogen is typically due to fertilizers and if you’ve applied fertilizer to your thyme, this is likely the cause of yellow leaves since thyme plants are have a tendency to be sensitive to nitrogen in soils due to their preference for medium to low fertility soils.
Thyme plants have been adapted to flourish in sandy soils that don’t hold much nutrients or water within southern South part of Europe.
So, when you plant thyme in your garden , it will not require extra fertilizer to be healthy, because a large quantity of nutrients is in contrast to the natural conditions that thyme plants have adjusted.
A high concentration of nitrogen in soil can cause an excessive growth of foliage, which could result in the plants to shrink or become wilted in appearance. This causes leaves to change color as a result of stress.
The amount of the essential oils (which influences the flavour and aroma) in the leaves is highest in plants that are exposed to full sunlight as well as in soil that isn’t overly nutrient-rich, so it is essential to use a an excellent potting mix that has the proper amount of nutrients that smells and tastes the best.
How to treat yellow thyme leaves with Nitrogen Burn
The solution to the problem of thyme leaves turning yellow because of the excessive use of fertilizers is to:
- Do not use any fertilizers that are added as they could cause more harm than good.
- Add soil amendments using Sand or even grit.
The addition of grit or sand helps reduce the amount of nutrients (particularly nitrogen) to mimic those sandy low – to medium soil conditions found in the thyme’s natural Mediterranean environment.
Sand that is too much than not enough, as sand improves soil drainage and improves the size of the pore which aids in the process of the process of respiration.
Repot the thyme (or remove it gently from the soil using the help of a gardening fork) and add around 30 percent horticultural sand, or grit to 70% of multi use compost.
The mix of compost and sand ensures that the thyme is getting the proper amount of nutrients needed to thrive and produce fragrant leaves. It may take a bit of time to recover from the burn to the nitrogen leaf, however, it will begin to show signs of recovery within the next few weeks.
Thyme’s Pot or Container too Small, (Nitrogen Deficiency)
Thyme plants may change color due to:
- The container or pot isn’t big enough (small containers have small capacity for soil, and consequently nutrients).
- The thyme’s plants are too close to each other (thyme must compete with light, space and nutrients, as well as water).
Thyme plants (as as with other Mediterranean herbaceous plants) are known to prefer a pot that is minimum 12 inches in diameter to ensure that the roots have enough room to grow and develop to allow them access to the nutrients.
With smaller containers and pots there is less space for soil, which means less nutrients and water, as well as less room for roots to grow which could impact the growth.
Thyme plants actually prefer low to moderate nutrient sandy soil , as it is the soil shape of their original Mediterranean habitat.
If the roots are bound to pots the soil’s nutrients may be depleted, resulting in the thyme turning brown because of a deficiency in nitrogen.
Thyme is a plant that naturally thrives in open spaces and is not one of the plants that likes to fight for nutrients, airflow and sunlight with other plants. This is why the thyme plants may change color if placed in close proximity to one another.
How do you solve it…
Transfer your thyme plant to larger pots of minimum 12 inches, with drainage holes at the bottom to allow any the excess water to drain away.
In a bigger container or pot, thyme can have enough room for roots to grow, which will allow the plant to develop large leaves that emit an intense aroma and distinct flavor.
A pot of this size can hold every soil element and nutrient that a Thyme plant needs to be strong and healthy.
Transfer thyme into a larger pot using multipurpose compost as well as some horticultural sand or grit. The thyme will begin to recover from its yellow appearance, and then turn into an attractive green within some weeks.
Don’t add any fertilizer that is artificial as the sand and compost mixture creates the thyme plant’s native soil conditions, with enough nutrients. Adding fertilizers can cause more harm than good because thyme is known to opt for soil that is poor.
If you are planting thyme in the garden or raised beds, ensure that the plants are not blocking the one as thyme requires the full sun for growth that is healthy and lush.
The thyme should be planted at least an 18-inch distance (measured from the planting site instead of the foliage that is outside) makes sure that each plant’s root system has enough room to grow and the additional distance allows for good airflow around the leaves , which reduces the chance of developing fungal diseases.
Grow thyme in full sunlight in a distance, in a pot that is minimum 12 inches in diameter and your thyme plants with yellow leaves will recover and look healthier in a couple of weeks.
The Spider Mites cause yellow Spikes on leaves
Another possible reason (but less frequent) could be the spider mites attacking the thyme plant. Spider mites resemble tiny spiders and are known to be a threat to the succulent growth on the underside of thyme leaves in spring.
Even if they’re in your yard, are often overlooked because they are surrounded by insects that eat them. number.
It is necessary to have an infestation in order to cause any harm However regardless of the size spider mites aren’t an issue that is serious and are easily dealt with.
The damage appears as tiny, yellow spots on the leaves that if not treated could cause leaf fall.
If you notice that spider mites have caused the leaves of your thyme plants to turn yellow The best option is to blast the mites using a hose, or get them removed by hand.
If you practice perseverance for a few weeks, that’s usually enough to resolve the issue. Cut off any damaged foliage using pruners to encourage new growth. The thyme will recover with no issues.
In most cases, natural gardens, insects and predators solve the problem and spider mites might not be a major recurring issue.
A different option would be to tackle the issue with chemicals.
I generally do not use of insecticidal soaps or pesticides on the leaves of herbs when I’m making use of them for cooking however, an insecticidal soap could be applied when spider mites pose a constant issue and the thyme plants you have are more ornamental than for cooking.
- Thyme plants usually change color due to root rot caused by moist soil. Thyme likes well-drained sandy soils, and cannot take to constant humidity. The signs of thyme suffering from root rot include yellow leaves, drooping or wispy appearance.
- Add a layer of horticultural sand to the soil in order to improve drainage and mimic the sandy conditions in the Mediterranean environment , to which thyme has adapting.
- The excess nitrogen in fertilizers or too little due to roots that are bound to the pot could cause thyme to change color to yellow. Thyme should be planted in a pot minimum 12 inches in diameter to avoid a deficit in nitrogen and avoid adding any fertilizer since this can cause the growth of leggy plants with less aroma and goes against thyme’s preference for soils with poor drainage.
- Spider mites can create yellow spots on the new growth. Clean spider mites with the hose or take them out by hand. Snip off any damaged growth to encourage new healthy growth. Avoid using pesticides if you are planning to use thyme for cooking reasons.