You might grow thyme because of its health benefits and how it brings lots of flavor to your meals. However, while it’s relatively easy to grow, you might find that your thyme plant is turning brown and dying. So, what causes thyme to die?
Thyme plants can die because they aren’t getting enough sunlight. Thyme needs to be in an area of the home or garden where it gets lots of natural light daily. Other reasons thyme can struggle to grow include if it’s overwatered or if its soil doesn’t have the correct pH.
In this article, I’ll explore these and other common reasons why your thyme keeps dying. I’ll also provide solutions regarding what you should do to bring your plants back to life.
1. You’re Overwatering Your Thyme
Thyme is a herb that you should care for by doing minimal work. It doesn’t want a lot of water, so don’t fall into the trap of watering it every few days, as this will make its soil too damp.
Thyme likes it when the soil is allowed to dry a bit before watering. Mature and established plants are more drought-tolerant. Therefore, it’s best to wait until the upper half of the potting soil is dry before watering again. For in-ground plants, check the soil’s upper 2-3 inches (5-7.6 cm) for dryness before adding more water.
It’s also good practice to stop watering your outdoor thyme plants a week before a predicted rainfall, as they will get enough water. You should only water thyme if your region goes through several weeks without any rainfall.
Being careful not to overwater your thyme plant will prevent root rot, a condition that can be fatal for it.
Some root rot symptoms include:
- Wilting leaves
- Leaves that become yellow or brown
- Stunted growth
- Sudden decline without any clear reason
- Rotten smell in the soil
It’s essential to treat root rot immediately, such as by reducing how much water you give your plant or pruning the damaged root sections and transplanting the thyme in fresh, well-draining soil.
2. Your Soil Doesn’t Have the Right pH
Plants require the right pH, whether it be acidic, alkaline, or neutral soil. Thyme plants require a soil pH that’s between 6.0 and 8.0, which has a pretty large interval and relatively easy to maintain. However, note that some nutrients become unavailable at extreme pH levels, so it’s best to go for the neutral 7.0.
Thyme normally doesn’t require many nutrients. Still, if you don’t have the right soil pH for your thyme plants, this will cause the following symptoms:
- Lack of growth
- Dieback
- Discolored leaves
You can test your soil’s pH with a home testing kit to measure soil pH, moisture, and how much sunlight your plants are receiving. This takes out the guesswork to keep your thyme plants alive.
3. You’re Not Pruning Your Plants
If you don’t prune your thyme plants, this can cause growth problems. The stems will turn woody in the plant’s center, and they’ll become brown and stop growing leaves properly.
However, pruning will remedy this issue quickly. Remove approximately one-third of the woodiest, oldest stems of the plant, and make sure you cut them back by half.
You should repeat this process every year to keep your thyme in good condition.
4. Your Potted Thyme Isn’t Getting Enough Drainage
Thyme needs well-draining soil whether in the ground or in pots. Therefore, your potting mix must be rich in sand or perlite to facilitate proper drainage.
If you’re growing thyme indoors, you also need to ensure you plant it in the correct pot that has good drainage. Make sure that your pot has drainage holes at the bottom. Also, pots that are made out of porous materials, such as terracotta, are ideal for growing thyme. The breathable material wicks away excess water, keeping the soil from becoming too wet.
5. You’re Giving Too Much Fertilizer
Thyme plants are low-maintenance because they don’t need rich, highly-nourished soil in order to grow. You also don’t have to feed them fertilizer unless the plants are showing weak or stunted growth. Over-fertilization will often result in fertilizer burn that can kill your plant when left unattended.
If your thyme is growing slowly in late spring or early summer, you can feed your plants a balanced liquid fertilizer to encourage them to grow. When using a 10-10-10 balanced fertilizer, make sure you apply it at half-strength so that you don’t encourage the plant to grow too many leaves. These will reduce the strength of thyme’s fragrant oils.
After fertilizing your thyme plants, make sure you water them thoroughly, as this evenly distributes the fertilizer’s nutrients through the soil and leaches out the excess.
6. Your Plants Are Getting Too Much or Too Little Sunlight
Although thyme plants need a lot of sun every day to thrive, too much sunlight can kill them. This is because the harsh sunlight puts too much stress on the plants and causes their leaves to become scorched.
On the other hand, too little sunlight for long periods will leave your thyme plant hungry as it cannot photosynthesize properly. This process produces energy for the plant so it can grow. Without it, the plant won’t receive the energy it needs, so it will die.
To prevent this, keep your thyme plants in areas of the garden or home where they will receive between 6 and 8 hours of direct morning light daily. Indoors, you can place them next to an eastern or southern window. Outdoors, you can grow them in the east garden.
7. There Is an Aphid Infestation
Thyme plants can be attacked by aphids, which are small insects that suck sap from plants. These common garden pests become problematic because they multiply rapidly. If you see them on the plant, wash them off with a strong stream of water, such as from a watering hose.
If this doesn’t work, you can try applying neem oil as long as it’s not yet harvest season. Otherwise, the neem oil solution will affect the flavor of thyme.
To apply neem oil, follow these tips:
- Mix one teaspoon of liquid soap in a liter (0.26 gal) of warm water. Add one tablespoon of neem oil. Alternatively, you can purchase a pre-made neem oil spray at retail shops or online.
- Put the ingredients in a spray bottle.
- Spray the neem oil solution on a small area of your thyme plants. Leave it for 24 hours, so you can see if there is any damage caused to the plants.
- As long as your plants don’t display any damage, spray your plant leaves with the solution.
- Reapply the solution to your thyme plants the night before watering your plant. Doing this once a week for 4-6 weeks will eliminate aphids and prevent them from affecting your plant again.
Alternatively, you can use commercially-available insecticidal soap, which is safer for herbs.
If you consistently apply effective treatment methods, plants can recover from having aphids. I’ve written an extensive guide about the topic. Don’t miss it: Can Plants Recover from Having Aphids?
8. The Humidity Level Is Too High or Too Low
It’s easy to assume that since your thyme plants don’t need a lot of water, they don’t need humidity, but this can set back your thyme plant’s growth and possibly even cause it to die.
Thyme requires 40% humidity. Fortunately, this amount is easy to maintain because the ideal indoor humidity level is around 30-50% anyway. That said, keep your thyme away from areas of the home that are prone to experiencing high humidity, like the kitchen or bathroom.
If the humidity is too low, you can use a humidifier or group your thyme around other plants that share the same humidity requirement. This will improve the humidity within the group as each plant transpires. Alternatively, you can use a humidifier.
On the other hand, if the humidity is too high, you can improve the air circulation by switching on a fan or using a dehumidifier.
9. Your Pot Is Too Small
Although herbs don’t require a lot of room to grow, you should be careful not to give them a pot or container that’s too small. This can kill the plant, which will struggle to get enough nutrients.
Ensure that the pot is approximately 4 inches (10 cm) in height and 4 to 6 inches (10-15 cm) in width. The maximum should be about 6 inches (15 cm) in height, as thyme has shallow roots that don’t require a lot of space in the soil.
If you’d like a more in-depth guide about repotting indoor plants and the benefits of having properly sized pots, you can read my other article here: The Ultimate Guide to Repotting Your Houseplants
10. Your Thyme Doesn’t Have Enough Potting Mix
Although small, the pot for your thyme plant needs to be large enough to contain around 1/4 gallon (1 liter) of potting mix so that it will have enough space to grow its roots.
Avoid using pure soil in your thyme pot, as this is too heavy. It easily becomes compacted, which will prevent air circulation for your plants. Your potting mix should contain porous materials like perlite or pumice.
11. You Moved Your Thyme Outdoors Too Soon
If you were growing thyme in containers indoors and now you want to move them out into the garden, be careful not to do this too quickly as it can shock your plants.
You must transfer your thyme plant only after acclimatizing it to give the plant a chance to get used to the new environment.
Here’s how:
- After planting the thyme into a new pot, leave it outside for a few hours during the day and bring it back inside.
- Slowly increase the time that you leave the pot outside over a period of 1-2 weeks.
12. Your Thyme Has Been Attacked by Icy Weather
If you’ve experienced a very harsh winter in your region, your thyme plant might turn brown and look dead. The good news is that your plant might not actually be dead but just dehydrated. Thyme can survive temperatures as low as -30 °F (-34 °C) but will halt growth until the temperatures become warmer.
To find out if your plant survived the winter, scrape the bark of some stems to see if they’re green. If so, the plant is still alive. You should avoid pruning it until new growth appears on the plant.
To prevent thyme from dying during winter, you should take some steps to protect it against the icy weather.
These include the following:
Avoid Overwatering It
Since thyme is ideal for dry climates, you should avoid watering its soil too much. Standing water will make it vulnerable to icy weather and frost damage.
Apply 2 Inches (5 cm) Of Mulch
Mulch, such as pine bark, will encourage the soil to drain properly so that the herb can withstand cold conditions. Mulch will prevent ground freeze and thawing, so the roots of the thyme plant won’t be exposed to harsh conditions.
Shelter Your Plants
Place pots containing thyme in sheltered areas of the home. This will protect them against strong winds and rain. On the other hand, in-ground plants will benefit from a burlap coat during snowy days. The material is breathable, so it won’t damage your thyme.
Watering potted plants before a freeze is a tricky business. If you live in a cold region, you should know how to water your plants during winter. Check out my blog post for more information on this subject: The Complete Guide to Watering Your Plants in the Winter
13. Your Thyme Isn’t Getting Enough Air Circulation
If you’ve noticed that your thyme plants are experiencing fungal diseases, this could be what’s killing them. Fungal diseases usually strike when thyme plants are planted in the ground without enough space between them to encourage enough air circulation.
This is especially problematic if you live in a hot or humid region. A common type of fungal disease is Alternaria blight.
This appears as follows:
- Holes in leaves
- Dropping or wilting leaves
- Small round brown, black, or yellow spots
To prevent this fungus from affecting your thyme plants, you should space the plants about 12 inches (30 cm) away from each other to encourage better air circulation.
14. Your Thyme Is Planted Next to Leafy Plants
It’s worth considering what companion plants you have for your thyme. While rosemary is a great herb that performs well when planted next to thyme because both of these herbs have similar watering requirements, if you’ve planted your thyme next to a leafy plant that sheds its leaves, this could be problematic for your thyme plant growth.
If you’ve already planted thyme with a leaf-shedding plant, don’t worry. You don’t have to transplant your thyme, but ensure you throw away any leaves that have decayed or dropped from the companion plant. If you don’t do this, the leaves could trap moisture around your thyme plant, causing issues such as mold, fungal diseases, and root rot.
15. There Is a Spider Mite Infestation
Spider mites are common garden pests that like to suck sap from a variety of plants, including thyme. If you’ve fed your soil too much nitrogen, this can produce proteins that make sap taste sweeter to pests, such as spider mites.
Signs your thyme plant has spider mites include the presence of what appears to be tiny black spots on your plant. Since spider mites are tiny, you might not see them clearly on the plant, so look out for fine webbing around your plant.
You can eliminate spider mites with insecticidal soap, which is regarded as a plant-safe pesticide with selective insecticidal property. The product can kill aphids, spider mites, and mealybugs. Luckily, most beneficial insects like ladybugs and lacewings remain unaffected by insecticidal soap.
