15 Reasons Your Rosemary is Turning Brown & Dying
If your rosemary is turning brown and dying, there could be a number of different reasons it's happening. Rosemary plants are hardy plants, but they can still fall victim to certain pests and diseases. In this article, gardening expert and former organic farmer Logan Hailey shares the most common reasons for a brown, dying rosemary plant.
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If you have a sick-looking rosemary plant, you may be wondering where you went wrong. Perhaps you gave it sunlight, water, and love, but it’s still turning brown and dying.
Rosemary is a laid back herb, but it can be a bit finicky about its soil and water. Fortunately, this plant is resilient and can probably be revived with a few changes in your care methods.
Let’s dig into 15 reasons why your rosemary might be suffering and how you can fix the issue!
Root Rot
Root rot is the most common disease of Mediterranean herbs like rosemary and lavender. This moisture-loving pathogen attacks the roots of the plant and turns them into a mushy, rotten mess.
When the roots begin to rot, the rosemary plant can no longer uptake the water and nutrients it needs to thrive. The result is brown-tipped leaves, dead branches, and a droopy appearance.
Root rot is especially problematic in waterlogged soils (like heavy clay) or container-grown rosemary without adequate drainage. Gardeners who tend to overwater their plants may create conditions that allow root rot to take hold.
Key Symptoms:
Root rot is fairly easy to diagnose when you dig up an infected plant. You will notice…
- Droopy, wilted appearance
- Yellowing or browning leaf tips
- Brown or black dead branches
- Entire sections of the plant die
- Brittle, dry appearance
- Gross, soggy smell from the roots
- Mushy, rotten roots when you dig up the plant
How to Fix It:
Prevention is essential for keeping this nasty fungus out of your rosemary, however there are still several steps you can take to save an infected plant, including…
- Gently dig up the rosemary plant
- Use sanitized pruners to remove any rotten roots.
- If the entire root system is mushy, it may be too late to save the plant.
- Dip or spray the roots into a diluted hydrogen peroxide solution (1 part peroxide to 2 parts water).
- Replant the rosemary in an extra well-drained area where the roots can breathe.
- Double dig and amend your soil with perlite, vermiculite, pea gravel, limestone, or peat moss.
- If growing in a container, ensure that the pot has a large drainage hole and a soil blend with lots of gravel or pumice.
- Provide a diluted dose of liquid kelp or seaweed to help the plant recover.
- Prune away any dead or damaged foliage.
- Only water rosemary when the upper few inches of soil have completely dried out.
- Locate the rosemary in a warm, sunny area.
Many rosemary plants can come back to life within 2-4 weeks. If the plant does not bounce back after transplanting, you may need to start over or address the potential issues described below.
Overwatering
Beginner gardeners sometimes show their herbs a little too much love. Rosemary does not require nearly as much water as your vegetable garden.
Mediterranean plants are accustomed to a dry summer climate with long periods of drought during the growing season. Rosemary actually enjoys dryness and will start to complain if it is overwatered.
Key Symptoms:
Underwatering and overwatering can sometimes cause the same symptoms in plants. To identify overwatered rosemary, look for…
- Yellow or brown leaf tips
- Leaves feel soft and mushy
- Whole branches turning brown
- Soil feels muddy, soggy, or waterlogged
- Droopy, heavy foliage
- Weak or floppy stems
- Any symptoms of powdery mildew or botrytis
- Any symptoms of root rot
How to Fix It:
The most obvious way to fix overwatering is to, well… Stop watering your rosemary. For Mediterranean herbs, overwatering is much more problematic than underwatering. Let the soil thoroughly dry out. Allow your rosemary to hang more on the drought side for a while.
If you’re growing in a container, treat rosemary more like a pothos plant or even a cactus. Instead of following a regular irrigation schedule, stick your finger in the soil and check the moisture before watering.
If the soil sticks to your finger, wait a few days and check again. The upper few inches of soil should feel dry to the touch before you give the plant a drink.
Underwatering (Drought)
Underwatering can look a lot like overwatering in many plants. Both problems can manifest as yellow or brown-tipped leaves and overall plant wilting. This is why it is essential to check the soil of your rosemary plant before watering.
- Stick your finger several inches into the soil and notice the texture.
- If your skin comes out dusty or with no soil sticking to it, the soil is probably very dry, and your rosemary needs a drink.
- If growing in a container, you can also turn the pot upside down and check the drainage hole.
- The soil may appear pale, dusty, or chalky.
Next, check the leaves. Underwatered rosemary tends to feel very brittle and dry. The stems and twigs easily snap because they are dehydrated. On the other hand, overwatered rosemary will have soft, very supple stems that may even feel mushy.
Key Symptoms:
While rosemary is quite drought tolerant, it still needs moderate amounts of moisture and will communicate with you when it is thirsty.
- Brittle twigs that snap easily
- Dry, crunchy leaves
- Yellow or brown color
- Barren, dry twigs where needles have fallen off
- Wilting and drooping
How to Fix It:
Dehydrated rosemary needs a hefty drink to regenerate itself. When watering your Mediterranean herbs, prioritize large, infrequent amounts of irrigation rather than small, frequent waterings. In other words, aim to give a generous dose of water all at once.
Water your rosemary until the surrounding 4-6” of soil appears thoroughly dark and moist. This deep drench will help penetrate lower roots and rehydrate the soil.
You may need extra water to rehydrate the mix if you have any hydrophobic (water-repellant) materials in your soil blend, such as peat moss or coco coir. Future waterings probably won’t need to be as heavy.
For rosemary in containers, pour water over the soil until it comes out of the drainage hole for about 30 seconds. Then, let the soil fully drain and rest. Check if the plant has perked up in the next 1-2 days. If not, you can safely add another drench of water.
How Often Should You Water Potted Rosemary?
Potted rosemary typically needs water once or twice a week, depending on the container size (smaller plants need more frequent watering), ambient humidity, and temperature.
The key to watering rosemary is to let the upper inches of soil dry out before watering again. Stick your finger in the pot and wait until it comes out clean. This indicates it’s time to give the herb a drink.
Poorly Drained Soil
Rosemary and its Mediterranean cousins (lavender, oregano, sage, etc.) all demand well-drained soil. These plants resent “wet feet” from sitting in soggy soil. Their roots need to breathe just like we do, so there needs to be plenty of pore space and aeration in the soil.
Key Symptoms:
The above issues of root rot and overwatering tend to coincide with poorly drained soil and have the same above-ground symptoms. At the soil surface, you may notice:
- Muddy or mucky soil appearance
- Algae or green slime growing on the top of the soil
- Clay soil appears cracked from getting drenched then drying on the surface
- A foul smell from the roots
How to Fix It:
You can improve the drainage of rosemary’s soil with the same methods you would use in the vegetable garden…
- Broadfork the soil to loosen up hardpans.
- This will help incorporate oxygen into the lower soil layers.
- Mix in a low-nitrogen compost made of decomposed wood chips or leaves.
- Add vermiculite, perlite, pumice, pea gravel, crushed limestone, peat moss, or coco coir.
- Double dig the planting hole before planting rosemary so the roots can reach out into the surrounding area.
Pruning Into the Wood
Pruning is one of the only maintenance requirements of perennial herbs like rosemary. However, if you prune the plant too hard and accidentally cut into the wood, it may harm your rosemary bush.
The woody branched center of a rosemary shrub is similar to the trunk of a tree. If you remove too much wood, it won’t survive.
Key Symptoms:
Over-pruning into the hardwood of rosemary can severely stress out the plant and potentially kill it. You may notice…
- Yellow or brown leaves from plant stress
- Disease or pests colonize the open woody wounds
- Whole sections of the plant dying or falling off
- Lack of regrowth from woody parts
- Plant collapse
- Sudden plant death after chopping into the wood
How to Fix It:
During your once or twice-annual rosemary pruning, focus exclusively on the soft, green plant parts. Pruning should be done on supple new growth rather than woody old growth. Never cut down more than two-thirds of the entire plant.
Your pruning process should only require hand pruners that can easily cut through small green twigs. If you need to use big loppers or a hack saw, you’re probably cutting into wood, and you should stop immediately!
Pest Pressure
Thanks to its strong fragrance, rosemary is not the target for many pests. However, some sap-sucking bugs may still attack a weak or young rosemary plant.
If you notice spittlebugs (white foamy places on the stems that look like someone spit on the plant), rest assured that these are completely harmless. You can spray them off with a blast of a hose.
Key Symptoms:
Aphids, thrips, leafhoppers, and mealybugs affect rosemary in a similar way. You may notice…
- Clusters of small bugs on the undersides of leaves
- Yellowing leaf tips where they fed
- Mold growth where aphids left sugary sap behind
- Spots on the leaves where leafhoppers fed
How to Fix It:
Pesticides are not necessary for a rosemary plant. Instead, spray your plant with a diluted neem solution, horticultural oil, or insecticidal soap. Be sure to spray the undersides of leaves as well!
You can also prune away infested branches and dispose of them. Plant rosemary with other plants that attract beneficial predatory insects, such as white alyssum, lavender, or sage.
Frost Damage
Rosemary is a warm-weather herb that cannot tolerate frosty temperatures. If your plant is exposed to temperatures below 32°F, it may shrivel and turn brown in the following days. In some cases, only part of a rosemary shrub will be frost-damaged, and other sections will survive.
Key Symptoms:
- Brown, dead stems
- Yellow or brown leaves
- Whole sections of dead leaves
- Overall pale, gray appearance
- Mushy or wilted plant crown
How to Fix It:
Rosemary can recover from some frost damage if it slowly thaws out in a cozy environment. Trim away only the damaged parts and protect the plant from future frosts.
Bring potted rosemary plants indoors for the winter. Gardeners in zones 7 and colder may need to grow rosemary in containers. Gardeners in zones 7 and 8 who plant rosemary outdoors may need to use a row cover or frost blankets to protect rosemary through cold snaps.
Excessive Heat
Rosemary loves the heat, but temperatures consistently above 100°F can stress out the plant if it doesn’t have enough water or airflow. This herb’s native Mediterranean climate is notoriously mild, which is why the plant does best between 55 and 80°F.
Key Symptoms:
Rosemary that has been exposed to extreme heat may look sunburnt (scorched, yellow-brown leaves) or display symptoms of drought.
How to Fix It:
Provide rosemary with extra moisture during periods of intense heat. Choose heat-tolerant varieties of rosemary that have been developed for the south (such as ‘Arp,’ ‘Albus,’ ‘Barbeque,’ or groundcover types like ‘Prostratus’).
Not Enough Sunlight
This aromatic herb prefers 6-8 hours of direct sunlight every day. If rosemary doesn’t get enough light, the most noticeable symptom will be a lack of fragrance.
Key Symptoms:
Shade
- Little to no aroma
- Stunted or slow growth
- Pale green foliage without the signature bright green color
How to Fix It:
Move rosemary to the brightest location possible where it can receive a minimum of 6 hours of direct sun. If the plant is getting shaded out by nearby trees or shrubs, consider pruning them back. Avoiding planting rosemary anywhere will fall under the afternoon shadows of your home or other structures.
Acidic Soil pH
Most Mediterranean plants enjoy a slightly alkaline soil that mimics the limestone rock of their native habitat.
A low soil pH will cause rosemary to turn yellow and start dying back. This happens mainly because the acidic soil prevents the plant from uptaking the proper minerals and nutrients it needs to survive.
Key Symptoms:
If you haven’t tested your soil pH, your rosemary plant may signal that the soil is too acidic by displaying…
- Yellow, red, bronze, or purple tinge on leaves
- Stunted growth
- Dead branches
- Brown spots on leaves
- Nutrient deficiencies
- Plant stress and vulnerability to diseases or pests
How to Fix It:
You can alkalize (raise) the soil pH near your rosemary by incorporating…
- Agricultural limestone (quickest option)
- Limestone gravel
- Small amounts of very clean wood ash (but use a very light hand with these)
- Compost
High Humidity
Mediterranean plants love the dry, warm air. Rosemary grows wild on windy coastal hillsides where there is an almost constant breeze. If you are growing rosemary in a humid climate, you may need to take extra precautions to maintain proper circulation through the plant’s leaves.
Key Symptoms:
Rosemary prefers 45-55% humidity and may complain if the air gets too moist.
- Mold growth
- Symptoms of root rot
- Symptoms of powdery mildew
How to Fix It:
You can’t dry out your climate, but you can ensure as much airflow as possible with proper pruning and wider plant spacing. In an indoor environment, you can use a dehumidifier or fan, and keep rosemary away from steamy areas like the dishwasher or shower.
Powdery Mildew
If your rosemary plants look like they have been dusted with white flour or a gray moldy growth, it is probably due to powdery mildew. This aggressive fungus attacks many plants in the garden and easily spreads in high humidity areas with poor air circulation.
Key Symptoms:
Powdery mildew is unlikely to kill your rosemary plant, but it can severely stunt the growth and harm the aesthetics of the herb. You may notice…
- A powdery white or gray coating on leaves
- Yellowing leaves
- Dropping leaves
- Deformed flowers
- Curling of leaves or branches
How to Fix It:
The most important way to keep powdery mildew out of your rosemary shrub is to avoid overhead irrigation! Always water the plant from the base to avoid wetting the leaves.
Powdery mildew is easily controlled with organic fungicides or neem oil applications. But it’s often easier to remove infected parts, throw them away, and thoroughly sanitize the environment.
Position the plant so it receives plenty of direct sunlight and airflow. You can also take the preventative measures described below for pruning and thinning your plants.
Lack of Pruning
Pruning is key to maintaining happy perennial herbs. Although the plant can survive without pruning, a once or twice-annual haircut will keep it looking healthy and attractive. Pruning ensures that your rosemary doesn’t get woody and continues to send out new flushes of growth.
Key Symptoms:
If you forget to prune your rosemary, it may start to show…
- Woody growth
- An unattractive shape
- Collapsed branches or plants
- Vulnerability to wind storms
- “Skeleton” looking plant without much foliage
How to Fix It:
Aim to prune rosemary in the spring after the first flush of flowers and again in the fall about 6-8 weeks before the expected first frost. You can use this opportunity to shape your rosemary into a hedge, gumdrop, or other shape. Never cut back more than one-third to one-half of the plant and always ensure that there is plenty of leafy material left behind.
Too Much Nitrogen
Unlike garden vegetables, rosemary typically does best without fertilizer or high-nitrogen compost. Over-fertilizing this herb can cause a nutrient imbalance that triggers excessive growth and predisposes the plant to a range of issues.
Key Symptoms:
Like a lack of sunlight, this problem primarily manifests as a lack of fragrance. The plant may also have…
- Overgrowth of green, leafy foliage
- Weak, floppy stems
- Yellow or pale leaves
How to Fix It:
In general, you should avoid fertilizing rosemary, especially with quick-release synthetic nitrogen. Only feed the plant with trace minerals like kelp, seaweed, or carbon-rich compost.
Overcrowded Plants
Rosemary shrubs can grow quite large. If several rosemary plants are growing too close together, they become more susceptible to root rot, powdery mildew, mold growth, and competing for resources.
Key Symptoms:
Like people, rosemary plants despise being crammed together like sardines. If your herbs don’t have enough space, they may have…
- Stunted or delayed growth
- Tangled branches
- Symptoms of low sunlight
- Symptoms of root rot
- Symptoms of powdery mildew
How to Fix It:
Plant rosemary shrubs about 1-3 feet apart, depending on the variety. Regularly prune the plants to ensure plenty of airflow between them. If plants start to get tangled together, you may have to dig up and divide every few years.
Final Thoughts
Once you understand rosemary’s needs, you can grow this herb with very little effort and never worry about yellow or dying leaves again.
Remember to:
- Plant in the best drained soil possible.
- Let the upper inches of soil dry out before watering.
- Make sure rosemary gets 6-8 hours of sunlight.
- Keep rosemary protected from frost.
- Prune twice a year.
