Rosemary (Rosmarinus officinalis) is an evergreen, a tender herb found mostly in warm and sunny climates, but can also be kept well indoors during colder periods. Whether you are growing your rosemary indoors or outdoors, you can run into problems with its care. If your rosemary plant or shrub is dying, there can be a list of various reasons for this. In this post, you will discover the main causes of rosemary plant dying and what you can do to save your rosemary plant indoors or outdoors.
The main causes for rosemary dying are overwatering, lack of sunlight, pests and diseases, high humidity. Other reasons that can cause rosemary to die are extremely cold winters and high rainfall.
Rosemary originates from Southern European countries bordering the Mediterranean Sea. Therefore, it is specially adapted to the conditions of the Mediterranean environment, which are hot and sunny. It is a popular culinary herb in home gardens, and is also used as a beautiful ornamental plant in the landscape. This herb has attractive needle-like leaves with a dominant fragrance and flavor, and is found in many Mediterranean cuisines. It is usually used to season meat, vegetables and eggs.
Rosemary grows best when transplanted from a cutting or seedling rather than from a seed. It is very versatile as it can be grown in the garden as well as in a pot indoors. This way, you can have an abundance of fresh leaves on hand while you cook. Pruning rosemary can be done at any time of year, although it grows more actively in the summer and spring. Plus, rosemary plants have beautiful blue flowers in the spring that are also edible.
Hard pruning is also harmful to the plant. For this reason, never cut more than 1/4 of the entire branches of the plant. Always use pruning shears to cut off 4-6 branch tips, then carefully pull the leaves off the stem.
Causes of rosemary plant dying
If your rosemary plant is dying, there may be several ways to save it from dying. But first, you need to find out what is possibly causing these problems.
- One of the most concerning reasons for rosemary plants dying indoors is the lack of adequate sunlight. Rosemary plants need plenty of sun, at least half of the day (6 hours is a bare minimum).
- Rosemary plants have roots that don’t like wet conditions. So, overwatering is one of the main reasons for root rot or loss of plant parts. Root rot eventually leads to the death of the plant.
- Winter can be detrimental to the rosemary plant. This evergreen herb likes hot and dry weather for its growth. Therefore, an extreme winter could be one of the reasons why the plant dies.
- Rosemary plants with overwatering or high humidity are very susceptible to pest infestations. These pests include spider mites, mealybugs, whiteflies and thrips. Indoors or outdoors, rosemary plants are more prone to powdery mildew and root rot.
- They also need to be pruned regularly. Lack of pruning, but especially over-pruning can make rosemary plants die.
- Too much fertilizer not only burns the plant roots, but also causes the rosemary leaves to turn yellow. It also reduces the aroma and culinary value of the leaves.
Reason 1: Lack of sunlight
As we have mentioned above, the rosemary plant is native to the Mediterranean, so it needs lots of sunlight and heat. Rosemary is also very heat tolerant, and they need full sun. 10-12 hours is optimal (at least 6-8 hours of full sun). If you have a rosemary shrub outdoors, make sure it’s not blocked by other plants. It should be in a spot that gets lots of full sun every day.
If you grow rosemary outdoors and bring it indoors for winter, they go from 10-12 hours (or at least 6-8 hours) of strong direct light exposure to 4-6 hours of indirect low light. It’s very difficult for rosemary plants to survive on this weak light or to produce enough energy to stay alive.
Since rosemary is native to Mediterranean environments, it requires well-draining soil, full sun, and infrequent watering for healthy growth. If you want to bring your rosemary plant indoors, it is better to help the plant adjust or acclimatize. You will need to do it by gradually moving it to a shady spot in your garden. Choose a sunny location for the rosemary plant; usually a south-facing window is a good spot.
Clear sign of lack of sunlight is when your rosemary starts losing its needles and dries out. If conditions are not corrected, rosemary with eventually die. If your rosemary is not getting enough light, transplant it to an area with more light (if outdoors) or take it indoors if possible. And if you are growing your rosemary indoors, you can use full-spectrum grow lights, fluorescent or LED like this, for 12-16 hours a day.
Reason 2: Overwatering
If you notice that the tips of the silvery-green, needle-like leaves are turning brown or black, then you may be overwatering the rosemary. Waterlogging will cause rosemary plants to die. They are sensitive to drainage and require well-draining sandy and stony soil.
Overwatering is one of the main reasons why rosemary plants do not survive in pots. In summer, rosemary plants can tolerate enough moisture. But in winter, the roots can suffocate if they have more than the required moisture.
Rosemary likes well-drained and moderately moist conditions. If you want to save your dying rosemary plants, it is better to transplant them to a well-drained, sunny garden. Or, place them in a suitable pot with adequate drainage holes in the soil. Water them less frequently, about once a week, and let them dry out between waterings. If you notice the top 1-2 inches of soil drying out, then water them no more than 1 inch of water at any time.
What is more, avoid overhead watering. That’s because overhead watering can lead to fungal infections (mildew). While your rosemary can bounce back from some overwatering in summer due to higher water evaporation, this mistake can lead to a plant death during colder seasons.
Reason 3: Extreme winter
Rosemary is a Mediterranean plant that does well in a sunny location, but is not cold tolerant. Most rosemary plants belong to a hardiness group of 8-11, and do not like below freezing temperatures. However, some varieties, such as ‘Arp’ and Madeline Hill’, are very hardy. They can survive temperatures of up to -5°Fahrenheit (-20.5 C).
Rosemary plants find it difficult to survive in extreme winters. It is better to bring the plants indoors before the first frost in autumn. However, rosemary prefers cooler temperatures in winter – 40-65 Fahrenheit (4-18 Celsius) are ideal.
This evergreen shrub will begin to lose its color, become dry and brittle, and eventually turn completely brown or yellow. Light winter damage will only kill a few branches. However, more severe winter damage will completely kill the roots and the plant.
To improve rosemary survival, plant them in a sunny, sheltered spot that avoids harsh winter winds. If frost damage has occurred, you will need to cut off the damaged stems and leaves. Then, you will need to transplant the rosemary plant into a large pot.
However, avoid cutting in winter when there is still a risk of frost. That’s because the area being cut is more susceptible to frost damage. Pruning of frost damaged parts should be done in spring when the weather is warm enough to stimulate new growth.
Mulching should be done in the fall, with about 2 -3 inches (5-7.5 cm) of mulch (straw, finely chopped leaves etc.) should be added on top of the soil. If you get below freezing temperatures (below around 20 Fahrenheit or -7 C), your plant might start dying. In this case, you can use a horticultural frost cover like this to cover your rosemary from rain and cold.
Reason 4: Pests and diseases
Although rosemary plants are quite resistant to disease, fungi and bacteria give them a hard time. A plant stressed by overwatering and high humidity is more exposed to pest infestation.
If you notice discoloration on stems, leaves or tissues, it could be that pests are feeding on them. Look more closely for tiny invaders and if you find pests, cut back the heavily infested plant parts. Immediately and then spray them with insecticidal soap like this.
Root rot and powdery mildew are the most common fungal diseases of the rosemary herb.
The symptoms of powdery mildew are white spores/powder on all parts of the plant. It usually occurs when the plant is in partial shade and the temperature is 60-80 F (16-27 C). That’s because powdery mildew thrives in damp and wet conditions. In case of a severe infection, the plant begins to shed its premature leaves/needles.
Giving the rosemary plant full sunlight throughout the day and spraying water on the foliage in the morning to wash away the white spores can be helpful in minimizing powdery mildew.
To control fungal infestations, apply a mixture of baking soda and water. You need to use organic pest/disease control, as rosemary herb is grown primarily for consumption. Neem oil like this is a very popular natural fungicide, effective against pests and completely safe for humans and pets. Same with insecticidal soap.
Learn all about rosemary diseases and pests here.
Reason 5: High humidity and root rot
If the rosemary plant wilts and sheds its foliage, which turns brown and yellow and looks brittle, root rot is the possible cause. Too much watering or poorly drained soil contributes to the conditions for the development of the root rot fungus.
If you notice these symptoms, stop watering immediately and protect the plant from rain to allow it to dry out. You can transplant the rosemary to another pot or location with well-drained soil and full sun.
Rosemary plants prefer drier conditions. To keep pest infestations away, plants need plenty of air circulation, a well-drained, sunny location and full sun. You can have a fan blowing on your rosemary plants for a few hours a day to protect them from pest infestations.
Full sun is important for rosemary growth because it increases the plant’s resistance to root rot and other fungal diseases and helps it recover. If you grow your rosemary indoors, make sure to use pots with lots of drainage holes. Avoid heavy clay soils for growing rosemary, and don’t put rocks on top of the soil. This will only decrease drainage and can cause your rosemary to die from rot.
In case of severe root rot, if the foliage or stem of the plant becomes mostly brown or yellow, then, unfortunately, it will not recover. It is better to replace the plant and treat the potting soil with an organic fungicide to prevent transmission of the fungus to new plants.
A great tip is to add a layer of gravel to the bottom of your rosemary’s pot. This will allow your potted rosemary to be raised in the pot slightly, and aid with drainage. Never bury stems of your rosemary in the soil, or it can lead to rotting as well.
Reason 6: Over-fertilization or lack of fertilization
If you notice that your rosemary herb has yellowed leaves and fewer flowers, you may not know the nutrient requirements of rosemary. It is not a plant with high nutrient requirements!
Since this herb is native to the warm climate of the Mediterranean region, it does best in sandy soils. Rosemary prefers sandy, nutrient-poor soil. If you fertilize your rosemary with high levels of nitrogen, it will burn the roots and cause yellowing of the leaves. Also, excess nitrogen will cause the foliage to grow faster, which of course comes at the expense of the flowers.
In this situation, you should stop fertilizing your rosemary and add more sand or grit to the pot. If your rosemary is in the garden, then it is better to fork the soil around the plant and add sand to the base of the plant, which will also improve the aeration of the plant. Your rosemary plant should recover next year if you do not use fertilizer and amend the soil with sand.
If your rosemary’s leaves are however turning pale green or yellow, it might need fertilizing. Use a fertilizer designed for leafy crops or herbs, like this.
Reason 7: Excessive pruning
While you can harvest the plant anytime during the growing season, you must be careful not to overdo it. Make sure to never harvest more than 1/4 of the whole plant. Otherwise, your rosemary will fail to recover and can start dying.
When pruning (for harvest), make sure to use clean snips or scissors. Only harvest from the upper part of the plant, avoid pruning the bottom part of the rosemary. If you want to use some rosemary for cooking, snip around 6-inch (15.2 cm) sections of fresh leaves. Pruning bottom parts (old leaves) is however important to promote bushy growth and good health of the plant.
Learn all about pruning rosemary in this post.
Reason 8: Wrong soil
As mentioned above, rosemary will start dying quickly if you grow it in a heavy, clay rich soil. Rosemary needs light, gritty and fast-draining sandy or stony soil. If you notice that soil is draining slowly and retains lots of moisture, amend it as soon as possible. Add some horticultural sand or grit to the soil and replant your rosemary into fresh soil afterwards.
Reason 9: Closely planted rosemary plants and overcrowding
Another reason why your rosemary might be dying is lack of space between the plants and overcrowding. That’s especially true for shrubs and rosemary plants outdoors. Overcrowding and closely planted rosemary plants will prevent optimal air flow to the plant. It can also lead to slower water evaporation, especially at the bottom of the plant, leading to infections and rot.
Make sure that plants are always spaced out properly. If your rosemary is dying from bottom up, prune old leaves and make sure there’s good drainage.
Why is my potted rosemary dying?
If your potted rosemary is dying, a few main reasons are lack of light, under or overwatering. Always make sure that your potted rosemary has enough drainage holes on the bottom to prevent waterlogged soil. Indoor rosemary is more susceptible to dying because they don’t get as much light.
Always place your indoor potted rosemary on the brightest windowsill and provide good air exchange. If you don’t get much sunlight, you can use full-spectrum grow lights like this for 12-16 hours a day.
Rosemary dying from bottom up?
If your rosemary’s leaves are dying from bottom up, it might mean that it’s simply losing old leaves. That’s why it’s important to prune your rosemary on the bottom. Pruning bottom leaves will promote new growth and make your rosemary plant bushier.
However, if your rosemary is dying on the bottom, examine it to see if there’s any mold or pests. If you do find it to be suffering from pests or mold, quickly use natural control and/or prune affected parts. This will help prevent the spread of the disease. Make sure that soil is well-draining as well, or it can cause crown/root rot.
Conclusion
If you are growing rosemary plants, proper care is important. Let’s conclude on how to prevent a rosemary plant from dying.
- You should provide them with well-drained sandy soil and at least 6-8 hours of sunlight (10-12 hours is optimal).
- Since rosemary plants are drought tolerant, water them when soil mostly dries out.
- Avoid overwatering the plants as this will cause pest and disease problems.
- Place potted rosemary plants on well-ventilated, sunny, south-facing windowsills.
- Regular pruning is necessary to maintain a bushier plant.
- Although regular pruning is important, avoid pruning in late autumn as pruning stimulates new leaf growth, which is then more susceptible to frost.
Rosemary can live up to 15 years with proper care. Always remember three basic principles for growing rosemary herb successfully: sun, good drainage and good air circulation.
Thank you for reading this post on rosemary plant dying. If you would like to learn more about rosemary care, please see this page.