If your rosemary plant is struggling to survive and thrive and looks like it might be dying, you’ll want to know why. As a hardy evergreen herb, rosemary is usually an easy herb to grow. But if it’s growing in poor conditions, or it’s exposed to stress, your rosemary may die. In this article, I’ll take you through the reason why your rosemary plant is dying, along with solutions for how to fix the problem.
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Why is My Rosemary Plant Dying?
Common causes of a rosemary plant dying are due to the wrong climate, watering problems, lack of sunlight, incorrect soil conditions, lack of soil nutrients, pests, disease and natural aging.
Let’s take a look at each cause in more detail and how to solve the issue for a thriving rosemary plant.
1. The Wrong Climate
Although rosemary can grow in a wide range of climates, it does prefers a warm, Mediterranean-like climate with low humidity.
In cold climates where temperatures dip below 23 °F (-5 °C) on a regular basis, rosemary plants will suffer from frost damage, which will kill the plant or at the very least, cause it to become stunted and weak. The same is true for climates with high humidity which can cause rosemary plants to develop diseases or attract pests.
Rosemary grows best in temperatures ranging from 55-80 °F (13-27 °C) in dry conditions with low humidity.
I’m in a temperate climate and fortunate to grow rosemary year-round. But if you live in a region with cold winters or high humidity, it’s still possible to grow rosemary successfully.
You can either grow rosemary as an annual or provide extra protection from frost during the winter months, such as covering your rosemary plant with a frost cover. You can also help reduce humidity by ensuring good airflow around the rosemary by planting them at least 2-3 feet apart and avoid watering too often. In very humid conditions though, your rosemary will struggle.
2. Watering Problems
Watering a rosemary plant can be a balancing act, as both overwatering or underwatering can cause the plant to suffer and even die. Generally though, once you figure out the best watering schedule for rosemary, you won’t have to worry about it at all. Rosemary is a hardy and even drought-tolerant plant once established so more often than not, in our attempts to give our plants the right conditions, it will be overwatering that will cause your rosemary plant to die.
Rosemary plants don’t like to sit in soggy wet soil, so it’s important not to overwater them. Overwatering can lead to root rot, which will cause your rosemary plant to wilt, turn yellow, and eventually die. Look for signs of overwatering which include soggy or waterlogged soil and yellowing or wilting leaves of the rosemary plant.
I find the best way to water rosemary is to check the soil moisture level with your finger or a moisture meter like this one, and water only when the top inch of soil is dry.
On the other hand, underwatering can also harm a rosemary plant, as it needs sufficient water to grow and thrive. As a Mediterranean plant, rosemary can tolerate drought and heat better than most herbs, but it still needs regular watering to stay healthy.
The telltale signs of underwatering your rosemary plant include dry or brittle leaves, a drooping appearance, and a lack of new growth.
To avoid underwatering, make sure to water your rosemary plant when the top inch of soil feels dry to the touch.
How Much Water Does Rosemary Need?
Generally, rosemary should be watered once or twice a week during the growing season, and less frequently in the winter when the plant is dormant. Keep in mind that the amount of water a rosemary plant needs can vary depending on factors such as the temperature, soil type and natural rainfall.
When watering, make sure to water the soil around the rosemary plant and avoid getting water on the leaves, as this can cause them to develop fungal diseases. This is less important in warmer weather, as the plant leaves will dry out quickly, but during cooler weather, you should use these tips along with watering in the morning to give the rosemary more time to dry out.
I’ve lost a number of rosemary plants due to too much rain over the years. So be sure to consider natural rainfall and adjust your watering during this time. Rosemary will cope better with underwatering than it will with overwatering it.
If you’re growing rosemary in a pot or container, you will need to water your plant more frequently as they tend to dry out faster. You should also have great drainage holes in your pots to prevent water from pooling at the bottom and creating soggy soil conditions.
3. Lack of Sunlight
Rosemary plants love sunshine and warmth, and they need at least 6-8 hours of direct or indirect light per day to grow well. If your rosemary is growing indoors or in a shady area, you might notice that its leaves become pale, thin, or leggy.
To solve this problem, you can move your rosemary plant to a brighter spot or supplement it with artificial light if growing indoors.
I’ve found growing rosemary outdoors in full sun is the easiest way to ensure vigorous and flavorful plants. Understanding rosemary is a Mediterranean herb, then providing it with its natural growing conditions will give you the best results.
You can transplant a rosemary bush if you need to provide it with more sunlight or better growing conditions. Just make sure it’s not too hot or the heat will stress the plant. So avoid transplanting rosemary in the height of summer.
4. Incorrect Soil Conditions
Although rosemary is pretty easy to grow – in fact my rosemary is left to its own devices most of the time – growing it in the wrong soil conditions can lead to poor growth and make it more susceptible to disease. In some cases, the wrong soil conditions can eventually cause the rosemary plant to die.
One of the most common problems with soil that rosemary doesn’t like, is if it’s too compacted or heavy. Clay-like soil leads to poor drainage and when this happens, the rosemary plant roots become waterlogged and cause root rot. This is bad news for your rosemary plant.
Soils that are too heavy also don’t allow the rosemary plant to take up essential nutrients which will cause poor growth due to deficiencies.
Rosemary grows best in well-draining soil with a pH of between 6.0-7.5. You can use a soil monitor like this to check the soil pH.
You can usually provide the right soil conditions for rosemary by amending it with compost and aged manure. However, if the soil is particularly alkaline, you can add lime and if it’s too acidic you can use a soil acidifier like this one.
5. Lack of Soil Nutrients
Although rosemary doesn’t need a great deal of fertilizer, it will grow best in fertile soil. Rosemary benefits from essential nutrients, such as nitrogen, phosphorus, and potassium, to grow and produce well. If your rosemary is growing in poor or depleted soil, you might notice its leaves turn yellow or brown and it loses its fragrance and flavor.
To boost your rosemary plant’s nutrition, you can amend the soil with compost, aged manure, or organic fertilizer designed for herbs. There’s no need to use too much fertilizer, an application during spring and then again in fall along with a top up of fish emulsion or bone meal during summer will provide your rosemary plant with everything it needs.
If your soil is already healthy, and you apply homemade compost and aged animal manure a couple of times a year, then this might be all your rosemary plant needs to thrive. Usually, this is all I do for my rosemary – and it’s very happy!
Rosemary plants can withstand many pest infestations, they are hardy and often look after themselves but there are a few pests that can cause damage if left untreated. Here’s what to look out for:
These pests are difficult to see with the naked eye as they’re so tiny, but their damage is visible. Spider mite damage shoes up as wilting, yellowing, and browning of the rosemary plant leaves. And infestations can spread to other plants in the area if left untreated.
To get rid of spider mites, try hosing them off with water. Failing that, my go-to solution is spraying them with horticultural neem oil.
These small, soft-bodied insects feed on the sap of rosemary plants. Aphids can quickly reproduce and form large colonies, causing leaf curling, wilting, and yellowing.
Spraying aphids with the garden hose is usually enough to get rid of them. Otherwise, you can use an insecticidal soap spray or neem oil.
Whiteflies are small, moth-like insects that feed on the underside of rosemary leaves. They cause stunted growth, wilting, and yellowing of the leaves.
If you discover whiteflies on your rosemary plant, neem oil will get rid of them.
These pests are small cottony insects that can cause yellowing and browning of rosemary leaves. Feeding on the sap of the plant, they cause stunted growth and wilting.
Insecticidal soap or neem oil works well to get rid of mealy bugs.
These tiny, winged insects cause distortion and discoloration of rosemary leaves. Thrips feed on the sap of the plant and can cause severe damage if left untreated.
Once again, neem oil will get rid of these pests. You can also use sticky traps like these.
It’s a good idea to keep an eye on your rosemary plant for any sign of pest infestation. Usually, it’s enough to look over your rosemary when walking around your garden or if you’re hand-watering the plant. Then if you see any pest damage, you can act early to get rid of them which will minimize any chance of serious damage.
Encouraging beneficial insects in your garden will also help keep the bad pests away. Lacewings and ladybugs will do the hard work of pest management for you. You can encourage insects such as ladybugs and lacewings with flowering plants such as marigolds and nasturtiums and gardening without chemicals. As a side note, you can also eat marigolds and nasturtiums!
Rosemary is generally fairly resistant to diseases, but it can still be affected by a number of diseases that can cause them to die. Here are a few of the most common plant diseases that can affect rosemary:
This is a fungus that thrives in moist soil conditions. Overwatering or poor soil drainage can create the perfect conditions for root rot to develop in your rosemary plant. Symptoms of root rot include wilting, yellowing, and brown or black roots. In severe cases, the rosemary plant can die.
To prevent root rot, make sure your soil is well-draining and not too moist. Avoid overwatering your rosemary and if planting in pots or containers make sure they have adequate drainage.
Powdery mildew is a fungal disease that can cause a white, powdery coating to form on the leaves and stems of rosemary plants. This disease thrives in humid conditions and can spread quickly, causing the leaves to curl, yellow, and fall off.
Preventative measures include adequate airflow around your rosemary by planting them at least 2-3 feet apart. Water at the base of the rosemary plant and not the leaves. This will help keep the plant dry. And if you do notice powdery mildew you can use a DIY Milk Spray which acts as a natural fungicide.
This fungal disease will cause the leaves of rosemary plants to turn brown and die. Blight is spread by spores and can be difficult to control once it takes hold.
Preventative measures include making sure your rosemary plants are well-spaced for good airflow (2-3 feet apart) and get plenty of sunlight. Avoid watering your rosemary from above and use the DIY Milk Spray above if you notice signs of Blight. You could also opt for an organic copper-based fungicide.
Rust is a fungal disease that causes orange or brown spots to form on the leaves of rosemary plants. These spots can merge together, causing the leaves to turn brown and die. Rust spreads quickly in humid conditions.
For prevention and treatment of rust, as above for Blight, provide good airflow with well-spaced planting. Plant rosemary in full sun and avoid watering overhead. Use a natural or organic fungicide if rust takes hold.
Verticillium wilt is a soil-borne fungal disease causing the leaves of rosemary plants to wilt, turn yellow, and die. Infected rosemary plants may also develop cankers on their stems. Verticillium wilt can be difficult to control and can survive in the soil for several years.
Unfortunately, there’s no cure for Verticillium wilt once a rosemary plant is infected. If you think your rosemary has Verticillium wilt, you should remove the infected plant and start again. Dispose of the infected plant to make sure it doesn’t spread. Plant your new rosemary in a different spot to avoid re-infection.
8. Natural Aging
Although rosemary can live for 10-20 years in the right conditions, its productivity really declines after 5-6 years. So if your rosemary is around 5 or 6 years old, you may notice it becomes woody, leggy, or generally less productive.
At this point, it’s probably worth planting a new rosemary bush. But if your rosemary is younger than 5 years and you notice these signs of aging, you can try to rejuvenate it with a good prune. For rosemary grown in pots or containers, you can try repotting with fresh soil.
During my early gardening days, I was surprised when my rosemary became woody and unruly. At the time I didn’t realize rosemary is best replaced every 5 or so years. Now when I notice a declining rosemary plant, I take cuttings to propagate new plants before replacing my rosemary. This way I always have a productive rosemary plant (or 3) in my herb garden!