Why Is my Rosemary Turning Brown? (9 Causes & Solutions)

Have you found yourself asking: “Why is my rosemary plant turning brown?” If so, I am here to offer you some possible causes and solutions.

No one likes to ask these questions, but the fact that you are means you care. So, I will do my very best to help you and your rosemary plant out.

After all, if you are anything like me, one of your biggest motivations for growing herbs is to enjoy time in your herb garden. This is your space to unwind from your 9-5, connect with nature, and relax. So, you don’t want to be adding more stress by struggling with sad-looking plants.

Throughout my gardening journey I have come across many, many issues – it is never fun. But, from that I can offer you this piece of encouragement.

With every failure in the garden, you can always harvest some knowledge. Then you will come back even stronger and more prepared the next year. So, let’s get to harvesting some knowledge!

What Causes Rosemary to Turn Brown?

Rosemary turns brown when its needs are not being properly met.

This can be due to incorrect soil type, watering routine issues, insufficient light, extreme temperature or high humidity, sudden changes to growing conditions, the current growing season, fertilization methods, air circulation issues, pests, disease, or an inadequate container if you are growing rosemary in a pot.

To find out why your rosemary plant is turning brown, you will need to do a little bit of an assessment. I would start with your rosemary’s most basic needs and then work out from there.

If you can catch the problem early enough, then your rosemary may be able to bounce back and recover.

Whether you are growing your rosemary indoors or outdoors, your troubleshooting process should be the same.

1. Soil Type

Rosemary prefers to grow in loose, sandy, or rocky soils. If you live in an area where it will overwinter, you will want to provide it with a yearly application of rich compost that is high in good organic matter. Other than that, it will be very happy in what other plants may consider poor soil. If you are growing rosemary in a pot do not use regular garden soil, make sure to use a well-drained soil by selecting a quality potting mix.

Rosemary does not like to have wet feet (roots). One of the worst things you could do is plant it in an area that is too wet. This can also happen when you use poorly draining soil. From this, your rosemary may develop root rot. Which would cause it to turn brown.

Another thing you could consider is the acidity of your soil, as rosemary prefers it more alkaline. I will admit I have never tested my soil pH. In general, most soil that you grow in should have a suitable pH level.

I would worry more about having good drainage and the available nutrients of the soil. I personally live in an area with very heavy clay soil, so I prefer to grow rosemary in a raised bed or pot with good drainage holes.

Assessment:

• Complete a DIY soil composition test with some water and a jar:
  • Add 1-2 cups of soil in a 1-litre clear glass jar. Add water just below the top of the jar. Shake up the water and soil for a few minutes. Then leave it to rest for 24 hours or more as needed. Once settled, you can see the layers showing your soil composition.
• Check the soil by digging through it. Does it seem light and fluffy or is it hard, and compact?
• Have your soil tested professionally for pH and composition at your local extension service, at some Universities, or purchase a soil test kit

Solutions:

• If your soil is too heavy:
  • In a pot – re-pot with better quality potting mix
  • In the groundwork in some sand, and rich compost around the area
• If the area is too wet – move to a new location
• If pH levels off – purchase a product to adjust up or down

2. Watering Routine

Water is such an important part of growing any plant. It is the way they take up nutrients, create healthy leaves, and maintain a nice big root system.

If you have overwatered rosemary, you can end up with root rot. When there is a lack of water, your plant can die of thirst.

Throughout my gardening journey I have found that if I ever have an issue with a plant, it is either because I have over or under-watered, or overwatered. It really can take some time and experience to get it right.

Another thing is that when you have very wet soil, it can lead to other issues such as fungus gnats or other fungal infections. Always make sure that excess water can drain away from the plant.

Assessment:

• Look at the colour of the soil:
  • Does it look light (dry), or dark (wet), is the soil pulling away from the sides of your container (very dry)
• How does the soil smell, fresh like a forest floor (good), or kind of like a swamp (way too wet)
• If in a pot – lift it to see how heavy or light it is – the lighter it is, the dryer it is
• Put one finger down into the soil to your second knuckle to feel for moisture

If you want to dive even deeper, then look at my post all about how often to water herbs. 

Solutions:

• Too dry – give a good soak of water
• Too wet – stop watering for a while, so the soil can dry out
  • In extreme cases when in a pot, you may want to re-pot with some new potting soil
  • If growing in the ground and you realize the area is too wet, then consider moving to a dryer location
• Develop a consistent routine to check your rosemary to make sure it gets enough water

3. Light Intensity

Rosemary will be its happiest when given 6-8 hours of sunlight each day. It is very sensitive to light levels and sudden changes in lighting could have a negative impact.

I read in one of my gardening books that this is one of the biggest reasons why rosemary can be so difficult to overwinter indoors. Rosemary is a slow-growing evergreen herb. So, it seems to prefer slow transitions from indoors to outdoors, and vice versa.

You will want to be sure to harden off your rosemary when moving outdoors if you have propagated it in the house. This is because it will not be used to the intense rays of the direct sunlight and can experience a sunburn (sun-scald).

Alternatively, you need to slowly adjust rosemary to lower indoor light levels if you are bringing it indoors for the winter.

Assessment:

• Observe your rosemary to see how many hours of light it gets each day
• How intense is the light?
• Did you just move your rosemary inside or outside?

Solutions:

• Growing indoors and not enough light:
  • Move to a sunnier window, or introduce a grow light
• When moving rosemary outdoors:
  • Provide short amounts of time outside (about 4 hours), until it can handle being outside full time
  • Overcast days are the best
• If has sun-scald – move to a less sunny spot while the newer leaves adjust to the sun
• When moving indoors:
  • Move your rosemary container to a spot with less light, continue for a few weeks, then bring inside and provide a sunny window or grow light

4. Temperature & Humidity

Rosemary is a Mediterranean plant which means it prefers to grow in more dry conditions. It will struggle in very humid climate. Rosemary also prefers to grow between 12-26 C (55-80 F) so it will struggle with extra high or low temperatures. It can survive winters with much cooler temperatures, however it will become dormant during that time.

Even though these are the norms, certain rosemary varieties will tolerate colder temperatures, or higher humidity a little bit better.

Do some extra research upfront and find a variety that is best suited for your area.

Assessment:

• Look at the growing conditions you have your rosemary in and see if it feels very humid or if there is a temperature extreme
• You can also use a thermometer or humidity reader if you want to get extra technical

Solutions:

• If the conditions are too extreme outdoors for your rosemary to be happy, then consider growing it indoors.
• You could also find micro-climates within your yard that may be better suited (for example: on a certain side of your home that may get more sun and less wind)

Here in Canada, our temperatures get way too cold for rosemary to survive, so I will bring it indoors if I want to save it.

5. Air Circulation

You want to provide good air circulation to your rosemary so you can avoid other issues. The best way to provide good air circulation is by regularly pruning, or providing a fan if you are growing rosemary indoors.

Regular pruning encourages fresh growth and maintains the overall health and shape of your plant. Plus, you can use the healthy clippings in your kitchen. Or to root and create more plants.

On the contrary, too much air circulation from strong winds can also be damaging and cause wind scorch which leads to dieback.

Assessment:

• Check to see if your rosemary is all entangled together
• Are you noticing a browner colour near the bottom of the plant where the light is being blocked
• Do you notice that light can easily move through the plant, and not many branches are overlapping – that is good.

Solutions:

• Provide a fan nearby if growing indoors in an enclosed space.
• Do some pruning and clean up any brown foliage or dead branches
• make sure not to prune more than 1/3 of the plant at a time
• It is best to prune the more flexible lighter growth and not cut too far into the woody stems
• Prune in early fall in cold climates, or twice a year in warmer climates

6. Growing Season

Another large factor to consider is the growing season.

Your rosemary may be turning brown due to frost damage, this will show up by your rosemary turning brown at the tips of the stems. It is a perennial down to zones 7-8 which means it can tolerate temperatures down to 10°F to 20°F (-12.2°C to -6.7°C).

Assessment

• Research your growing zone to see what temperature you get to and if rosemary can overwinter
• Think about the time of year – perennial herbs always look a little worse for wear in the spring but should perk back up as the weather warms

Solutions

• Bring rosemary inside to overwinter if temps will be too low
• If it is early spring, wait a bit and see if your rosemary starts to green up as the weather gets warmer

6. Fertilization Methods

If you are growing your rosemary in the ground year-round, then all you need is a nice layer of compost once per year to keep it happy.

If you are growing rosemary in a pot, you will want to fertilize according to the directions on your fertilizer. I use an organic fertilizer since I will be consuming the leaves from this plant later.

The key is not to overfertilize. Some gardeners will have a problem with too much fertilizer and mistake that for a lack of fertilizer. Then to try and fix it they introduce more fertilizer which just makes things worse.

Assessment

• Think about how your rosemary is growing – is it in a pot or the ground?
• Have you provided it with fertilizer recently before you noticed it turning brown?

Solutions

• If you may have over-fertilized, then continue your watering routine without any fertilizer – will help to dilute and drain.
• If you think your rosemary is lacking fertilizer, then provide a very light application with around a 5-5-5- NPK.

7. Container Type & Size

It is important to provide your rosemary with a suitable container.

You want to match the size of the container to your rosemary. As your rosemary continues to grow, you should be potting it up. A larger container is always best because you will not need to worry about watering as much, and it will provide more room for a healthy root system.

Another thing to consider is the material your container is made of. Generally, you will find rosemary growing in terracotta pots because they are more porous and can allow moisture to escape. It will also not heat up the same way that plastic or metal would.

The container material will depend on your growing climate. For example, if you are growing in a very dry environment you may want a less porous material to keep moisture in longer.

Assessment:

• Dig your finger down into the soil to see if the soil is very hard and full of roots
• Gently remove your rosemary and look at the bottom of the root ball to see if there are many roots all clumped together, and winding around the bottom

Solutions:

• If your rosemary has become root-bound, then pot it up into a larger container
• If you are finding that the soil is too wet, find a pot with more drainage
• If your pot is drying out too fast consider using a less porous material or adding mulch to the top of the pot

8. Pests & Disease

Pests are not generally a problem for rosemary as it has a very strong scent that can actually repel insects.

That is one of the reasons why they say to plant rosemary by your garden gate. Although, I don’t think I have ever seen a bug in my garden as polite as to use the front gate. They kinda just go wherever they please.

If your rosemary plant is already struggling with other issues, then it will be more prone to pests. Those bad garden bugs can always pick up on a sick plant and then they just focus in on it to make matters worse.

But if your rosemary is happy and healthy then I would doubt you have a pest issue.

Disease can come in the form of powdery mildew.

Assessment:

• Look for pests or signs of pests on your plant
  • Bugs
  • Bite marks on leaves
• Identify which type of pest you are dealing with: you may see spider mites, or aphids on your rosemary
• Look for signs of white powdery substance on your leaves (powdery mildew)

Solutions:

• Do not use chemicals to remove pests as you are most likely planning on using that rosemary in your kitchen
• You can find many natural ways of deterring pests
• keep a healthy, tidy garden which deters pests
• Plant things that will welcome beneficial bugs
• Keep good airflow around your plant
• Neem oil can be used to get rid of pests

Can you use rosemary after it turns brown?

When harvesting herbs, you want to do so when they are at their healthiest and freshest. This way you will get the best flavour and the most benefit out of the plant. For this reason, I would personally not use rosemary after it turns brown.

Will rosemary come back after turning brown?

Brown rosemary plants can come back. It all depends on how brown it has become, and how long it has been that way. If you make sure to provide the proper care, you can have a healthy rosemary plant with nice green leaves once again.

It may take some time to correct the issue and in some severe cases, you may need to start over with a new plant.

Ok, so now that you know some of the common causes and solutions, it is time to go out there and start your assessment. Then you can develop a treatment plan tailored to your situation. The sooner you take action the better. I wish you and your rosemary all the best.

Also, feel free to add any extra suggestions or questions in the comments.

Until next time!