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Why is my Rosemary Plant Turning Brown and What to do

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Do you have a rosemary plant turning brown and you’re not sure what to do? Well, if you’ve grown plants at all, then chances are, at least one has died on you. Chances are though, one brown limb on rosemary isn’t the end, and whatever plants you may happen to be growing, the possibility of brown leaves is almost a given.

​Whether you’re growing a rosemary plant indoors or out, then you may run into the real possibility that the leaves of your hardy herb are turning brown. There are a  number of reasons that rosemary leaves can start turning brown. So let’s take a look at what may be causing the brown leaves, and learn how we can prevent this or fix it if the plant is already suffering. Let’s get started. 

Should rosemary turn brown?

When it comes to rosemary plants, it’s important to understand what is considered normal and what should raise concern. One common question that comes up is whether rosemary should turn brown. The short answer is, yes, it’s normal for rosemary to experience some browning. 

However, it’s crucial to differentiate between normal browning and excessive browning that indicates an underlying problem. Rosemary is in many climates a perennial herb, which means it should not completely die each year, but if you live in an area with extreme cold and snow, you want to consider some protection for your rosemary in the winter months or bringing indoors if it’s potted. (See my full post on Tips for Growing Rosemary.)

So while rosemary plants should naturally have some browning, if there’s an excessive amount of leaves affected, it may be attributed to one of the following reasons. 

Improper Watering Issues

Proper watering is essential for the health and well-being of all plants, including your rosemary plant. While it may seem simple, it’s easy to make mistakes that can lead to brown leaves. Let’s check out some common watering issues that can lead to your rosemary turning brown.

Over watering

One common error is over watering, and I’m sure we’ve all been guilty at some point or another. Rosemary prefers well-draining soil, and excessive moisture and poor drainage can cause the roots to become waterlogged, leading to brown, wilted leaves. 

Fix: Use the fingertip rule to determine if your rosemary plants already have enough moisture. (Insert your finger about an inch down into the soil. If the soil is damp on your fingertip, don’t water yet.) Also, to avoid over watered rosemary in pots, be sure you’re using a container with good drainage holes. This will help excess water seep out. 

rosemary in a clay pot

Under watering

On the other hand, under watering can also be detrimental. Insufficient water supply can result in dry, browning leaves and a weakened plant overall. You should be able to tell the difference between an under watered an over watered plant pretty easily by looking at the soil, and an under watered plant would also have a droop.

Fix: Provide enough moisture to keep the soil evenly moist, but not soggy, allowing the roots to breathe. One effective technique is to water deeply but infrequently. Instead of giving your plant small amounts of water every day, thoroughly saturate the soil and then allow it to dry out slightly before watering again. This mimics the plant’s natural environment, where it experiences periodic cycles of precipitation and dry weather.

Root Rot

Root rot in rosemary is a fungal disease caused by pathogens like Phytophthora or Rhizoctonia, thriving in overly moist soil. Symptoms include wilting, yellowing, and stunted growth, with affected roots appearing brown and mushy. This is why it’s a good idea to check a plant’s roots before purchasing from a nursery. Try not to bring home a plant that is already showing signs of this issue. 

Fix: To prevent root rot, ensure well-draining soil, moderate watering, and proper plant spacing. In severe cases, fungicides may be used, but early detection and good watering practices are crucial for effective management.

​More watering tips for rosemary

Another thing to consider is the time of day when watering. It’s best to water your rosemary plant in the morning, allowing the excess moisture to evaporate throughout the day. This helps prevent the growth of mold or fungus that can contribute to browning leaves.

Additionally, the type of water you use can impact your rosemary’s health. Tap water often contains high levels of minerals, such as chlorine or fluoride, which can accumulate in the soil and harm the plant. Using filtered or distilled water can help help this issue and promote healthier growth. I realize that we can only reasonably do what we can, so if you don’t have a filter system or rain barrel at home, then just use what you’ve got. No need to break out the bottled water for your plants. 

Pest Infestation and Diseases that turn Rosemary Plants Brown

In addition to improper watering techniques, pest infestation and fungal diseases can also lead to brown leaves on your rosemary plant. Several common pests can wreak havoc on your herb garden causing brown leaves on rosemary bushes and plants as well as other garden favorites. 

Aphids on Rosemary

Aphids can cause brown leaves on rosemary plants by feeding on the plant sap, which reduces the plant’s overall health. As aphids feed, they secrete a sticky substance called honeydew, promoting the growth of sooty mold on leaves. The combination of nutrient loss from feeding and the presence of sooty mold can lead to the discoloration and browning of rosemary leaves.

Fix: ​See my full post on How to Get Rid of Aphids, but you can initially just try spraying them off with good blasts of water. You’ll want to be consistent for checking for aphids once they’ve been spotted though because their tiny size makes them tricky to guarantee they’re all gone. 

Spider mites

Spider mites can cause brown leaves on rosemary plants by piercing plant cells and extracting sap, leading to cellular damage and reduced chlorophyll content. As a result, affected leaves exhibit discoloration and eventually turn brown. Also, the fine webbing produced by spider mites may add to the appearance of damaged foliage on rosemary plants.

Fix: Much like aphids, you can initially try good blasts of water or simply wiping leaves with a wet cloth. Due to rosemary’s small leaves, this may be not be the most effective. Insecticidal soap is also a good option for spider mites and easy to either buy at your local garden center or make at home in a spray bottle. 

Whiteflies

These tiny creatures feed on the sap of the plant, which can cause discoloration and damage to the leaves. If you notice small, white flies anytime you move the plants limbs or sticky residue on your rosemary, it’s likely that these pests have taken up residence.

Fix: One simple solution is to spray your rosemary with insecticidal soap, a mixture of water and mild dish soap, which can help suffocate and repel the pests. You can also explore organic insecticides specifically formulated for garden use to combat the infestation effectively. There are some decent options out there if you need to go this route. (See my full post on How to Get Rid of Whiteflies.)

Alongside pest infestation, diseases can also contribute to brown leaves on your rosemary plant. These may be more difficult to “fix” and prevention is the key here.

Powdery mildew

Powdery mildew is a common fungal disease that can show up as a white powdery coating on the leaves of the rosemary plant. This disease thrives in humid and crowded conditions, so it’s crucial to provide enough spacing between your plants and ensure good air circulation. 

Fix: Neem oil is often recommended as an organic treatment for powdery mildew, as it has antifungal properties that can combat the infection. Find good quality neem oil at your local garden center. 

To prevent and address diseases, it’s essential to maintain a clean and healthy garden environment. By being vigilant about pest infestation and diseases, you can keep your rosemary plant healthy and lush. Remember, your eyes on your plants is really the preventative there is!

Environmental Stress Factors that Cause Rosemary Plants to Turn Brown

In addition to pests and diseases, environmental stress factors can also contribute to the appearance of brown leaves on your rosemary plant. Did you know that just like people, plants can get stressed out as well? And one sign of a stressed out rosemary plant can be brown leaves. Here are some environmental factors that you may want to consider.

Extreme Heat

While rosemary plants enjoy full sun and warm weather, extreme heat can put a strain on your rosemary plant. High temperatures can cause the soil to dry out quickly, and the lack of water can cause the leaves of your rosemary to turn brown and the overall heath to suffer.

Fix: Consider using a shade cloth for in-ground rosemary plants and move potted rosemary to an area with partial shade if you’re experiencing extreme heat in your area. 

Extreme Cold

On the other hand, freezing temperatures can damage the plant’s delicate leaves, leading to discoloration and wilting. Rosemary is a hardy plant and can certainly take some cold temperatures (especially if they are planted close to the house, where some heat and protection are avaiable), but frost damage can take a toll if it gets excessive.

Fix: To protect your rosemary from temperature extremes, consider bringing potted plants indoors during frosty winter nights and covering in-ground plants with a sheet or towel.

Poor Soil Quality

Where your rosemary is planted is incredibly important for it’s ability to thrive. The quality and composition of the soil in which your rosemary plant is growing can also impact its health. Rosemary thrives in well-drained soil with a slightly acidic pH. If your plant is showing signs of stress, it may be worth testing the soil to ensure it has the right balance of nutrients and pH level. (See my full post on How to Test Garden Soil if you’re not sure how to get started.)

Fix: If necessary, you can amend the soil by adding organic matter such as compost or sand to improve drainage and promote healthy root development. If your plant is in a container, consider how long it’s been potted, and if necessary, re-pot with fresh soil and a larger container. (See my post to make your own DIY Potting Mix.)

Too Much Fertilizer

Finally, be mindful of fertilizer usage. While rosemary plants benefit from occasional feeding, excessive fertilizer application can lead to nutrient burn and brown leaves. I honestly never fertilize my rosemary bushes, but if you must, use a balanced, slow-release fertilizer or a diluted liquid fertilizer according to the instructions provided. (For most of my general fertilization, I like Espoma’s Garden Tone, but use what you like best!)

Fix: If you’ve over used fertilizer, give the plant a good long break and see how it responds. Also, avoid applying fertilizer directly to dry soil or during periods of drought, as this can further stress the plant.

Not Enough Sunlight

Did you know that rosemary is a plant native to the Mediterranean? All of that sunshine! If your aromatic herb is turning brown, consider the amount of sunlight your rosemary plant is receiving. Insufficient sunlight can weaken the plant and lead to brown leaves. 

Fix: Rosemary thrives in full sun, so ensure it is placed in a location that receives at least 6-8 hours of direct sunlight per day. If necessary, you may need to relocate your plant or provide additional artificial light, such as a grow light if the light it’s receiving indoors isn’t enough.

Rosemary Needs Pruning

Remember when I mentioned above that having brown leaves can be normal on a rosemary plant? Well, be sure when you do see leaves that are brown and completely dried out that you go ahead and prune those off. This will do two things, keep any fungal infections from hopefully spreading and create more airflow for your plant. There’s no need to have unproductive limbs and leaves left on healthy plants. 

Fix: As with all pruning, be sure you’re starting with a clean pair of sharp pruners. If you suspect there’s some powdery mildew on your plant or even those tiny pests, clean your pruners thoroughly afterwards before storing them. 

Physical Plant Damage

There’s also the real possibility that your rosemary plant sustained damage from improper pruning into the hardwood or a broken limb due to weather, pets, etc. Be sure to always check the base of any limbs whose leafs are turning brown to make sure there’s isn’t some obvious trauma to that particular part of the plant. 

Fix: If you do notice damage to a limb and the leaves are turning brown, it’s a good idea to go ahead and prune that limb off. The brown leaves are a sign that they are dying, so there’s a slim chance you’d be able to save it. 

rosemary plant in a pot

More Help with Herbs

Still have questions about growing herbs? I have quite a few articles all about the best way to grow, prune, and harvest a variety of herbs in your home vegetable garden or herb garden. I’d love to help, so check out these related articles:

How to Propagate Rosemary from Cuttings: Learn how to grow young plants from the one you already have! You’ll be able to grow more plants or gift them to others!

How to Prune Basil for Larger Yields: Want to grow huge basil plants in the summer? Learn how to easily prune them to get them to bush out and produce even more basil!

How to Plant, Grow, and Harvest Thyme: One of my favorite container herbs to grow year round is thyme. It’s perfect in so many culinary dishes and incredibly easy to grow. Find out how to grow this delicious herb!

​How to Save Parsley Seed: Learn how to save seed from this abundant herb, and you’ll be able to grow parsley for years to come (and give some seeds to others to use)! Parsley is perfect for growing in any size garden, so saving the seed 

By addressing these potential issues and implementing the appropriate fixes, you can significantly improve the health and appearance of your rosemary plant. 

By understanding the causes of brown leaves on your rosemary plant and following the steps outlined in this article, you have the power to restore your plant’s vibrancy and ensure its long-term health. Remember, brown leaves are not a permanent state for your rosemary – they are a signal for you to take action and provide the necessary care. 

Don’t let those brown leaves overshadow the beauty and potential of your plant. Take action today, armed with the knowledge and guidance you’ve acquired. As you nurture your rosemary back to health, you’ll witness the transformation from brown and wilted to green and thriving. And in that transformation lies the true beauty and resilience of nature. So go ahead, give your rosemary plant the care it deserves, and watch as it rewards you with its aromatic leaves and enduring beauty.