Rosemary is a Mediterranean herb that thrives in full sun, well-draining sandy soil, and often does need much water.
The reason for rosemary dying is usually because of overwatering and slow-draining soils which promote the conditions for fungal disease pathogens such as root rot, that cause the rosemary leaves to turn brown and die back. Rosemary turns yellow with a dying appearance when in too much shade.
Here is a quick summary of the most common reasons for rosemary dying:
| Causes: | Reasons for Rosemary Dying: |
|---|---|
| 1. Overwatering (drooping appearance with brown leaves). | Rosemary is drought-resistant and prefers sandy soils that drain sharply. Overwatering creates too much moisture around the roots causing root rot. |
| 2. Soil drains too slowly. | Rosemary grows on hillsides in gritty sandy soil. If the soil retains too much moisture or is naturally boggy then this causes root rot. |
| 3. Not enough sunlight. | Rosemary is adapted to growing in full sun. Too much shade causes the rosemary to die back often with yellowing foliage. |
| 4. Soil is too acidic. | Rosemary can grow in soil pH 6-7.5. If the soil is too acidic then the roots cannot uptake the nutrients they need and the rosemary turns yellow and dies back. |
| 5. Wrong climate for rosemary. | Rosemary prefers mild Winters is susceptible to frost damage in cold Winters and can often die due to cold wet soils causing root rot. |
| 6. Conditions too humid for rosemary. | Rosemary grows naturally on hillsides with lots of airflow. Excess humidity slows down evaporation and increases the risk of root rot and other fungal diseases. |
| 7. Heavy pruning can kill rosemary. | Rosemary like lavenders do not like being pruned back into old wood as the old wood does not rejuvenate and grow new stems. Only the top third of the rosemary should be pruned. |
| 8. Too much fertilizer causes rosemary to turn yellow with a droopy appearance. | Rosemary are adapted to grow in in sandy soils with medium to low fertility. Too much nitrogen in the soil from fertilizer causes the stems to turn droopy and turn yellow with excess growth that is more vulnerable to pests and disease. |
Keep reading to learn why your rosemary is dying and how to implement the solutions to save your rosemary…
1. Overwatering Rosemary (Drooping Appearance with Yellow or Brown Leaves)
The most common reason for rosemary dying is because of overwatering. Rosemary is a drought-resistant herb that prefers dryer conditions. Watering too often creates damp conditions that promote root rot causing the rosemary to turn brown and die back.
Rosemary is a native to the Mediterranean region of Europe where it thrives in scorching Summer sun, with sandy soils (that dry out quickly) and infrequent rainfall.
Rosemary requires infrequent watering to stay healthy, grow, and produce its intense and distinctive aromatic leaves for cooking.
Due to the rosemary’s drought tolerance, it is very sensitive to the affects of overwatering when cultivated by gardeners and after the first year of planting, rosemary should generally only be watered in times of exceptional drought.
Established rosemary plants in temperate climates often do not need any additional watering at all, as they can attain all the moisture they require from rainfall, even during the dryer Summer months, if they are planted in garden borders and raised beds.
Pots tend to dry out much quicker (particularly as rosemary prefers full sun) so watering once every 2 weeks is often appropriate in Summer. If you are watering rosemary plants more often the once every 2 weeks then you are overwatering rosemary.
If rosemary is watered frequently, so that the soil is always moist or saturated then this interferes with the root’s ability to uptake moisture and nutrients which can turn the rosemary leaves yellow or brown depending on the severity of the overwatering.
Fungal disease pathogens such as root rot and Botrytis also thrive in damp soil conditions which is a major cause of rosemary turning brown or black, drooping, and dying back.
Keep in mind that rosemary (along with other Mediterranean herbs) has the ability to tolerate drought in some of the hottest and driest areas of Europe, so when it comes to rosemary dying, overwatering is almost always the problem rather then underwatering.
How to Save Overwatered Rosemary…
If your rosemary is showing signs of stress from overwatering then stop watering immediately and protect the rosemary from any further rainfall if possible (move potted rosemary undercover if heavy rain is forecast in your area) to give the rosemary’s roots a chance to dry out and an opportunity to recover.
Here is a table for reference on how often you should water rosemary:
| Conditions for Rosemary: | How Often to Water Rosemary: |
|---|---|
| Newly planted rosemary: | Water once per week for the first four weeks. |
| Rosemary in the first year after planting: | Water once every two weeks (during Spring and Summer) if there is little or no rainfall during this period with a generous soak to encourage the roots to establish. |
| Established rosemary (more the 1 year after planting): | No watering is required unless weeks of pronounced drought. |
| Rosemary in pots: | Water once every two weeks during Summer (if there has been no significant rainfall) with a good soak. |
| During Winter: | Rosemary is dormant in Winter and does not require any watering. |
Due to rosemary’s resistance to drought, most rosemary plants do not require watering, however rosemary in pots can require a watering schedule as some variables can increase how quickly the soil dries out, so I wrote another article explaining all the best practices for watering rosemary in pots in different climates and conditions.
Saving Rosemary with Root Rot…
To determine whether rosemary has root rot, it is important to inspect the roots. Healthy rosemary roots should be light brown, feel firm, and not have any strong or distinctive smell.
Rosemary roots with root rot are darker brown with a mushy texture, rotten appearance, and smell unpleasant.
- Snip back any unhealthy diseased roots with a sterile pair of pruners back to healthy growth. Wipe the blades of your pruners with a cloth soaked in alcohol disinfectant to prevent spreading fungal pathogens from unhealthy roots to otherwise healthy roots.
- Replant the rosemary into new soil that is roughly around 70% peat-free multipurpose compost to 30% sand to promote good drainage and plant into a new pot.
- Throw the old soil away and wash out the pot (if you are growing potted rosemary) with disinfectant as the old soil can harbor the fungal pathogens responsible for killing the rosemary.
- After replanting the rosemary give the pot a good soak and place in partial shade whilst the rosemary recovers.
If you do not snip back the diseased roots the fungal disease spreads and the rosemary dies back.
If there is extensive root rot then there may not be enough viable healthy roots remaining and the rosemary could die back, but by pruning the diseased roots you are giving the rosemary the best chance of recovery.
Another factor to consider is whether your soil drains quickly enough as rosemary has adapted to growing in sandy, gritty soil as slow-draining soils cause the same symptoms as overwatering rosemary.
2. Soil Drains Too Slowly
Rosemary plants die back if they are in soil that drains slowly or holds too much moisture. Clay, compacted soil, or soil unamended with sand retains too much moisture around the roots of the drought-resistant rosemary causing the leaves to turn brown and die of root rot.
Rosemary has specifically adapted to growing in sandy or gritty soil which promotes very fast drainage and does not hold onto moisture and therefore cannot tolerate persistently damp soil.
Rosemary requires soil with a high inorganic content which creates a porous structure that allows for good drainage and root respiration.
Even standard multipurpose compost holds too much moisture and should be amended with horticultural sand, grit, or perlite to help replicate the preferred soil conditions of the rosemary’s native Mediterranean environment.
The rosemary’s signs of stress from slow-draining soil are the same as overwatering (as it essentially has the same effect of too much moisture around the roots) with a drooping appearance, brown (or yellow) foliage and an overall dying appearance.
The Solution…
Scale back any watering of your rosemary if it is showing symptoms of root rot as this will quickly compound the problem.
The most effective way to save rosemary from dying in damp soil is to replant it into new a pot as pots have much more favorable drainage conditions than garden borders or raised beds. Choose a pot that is around 12 inches across with a proportional depth to ensure the rosemary’s roots have enough room to establish.
(Read my article, choosing the best pots for rosemary).
Pots also have the added advantage that you can specifically customize the soil conditions to suit rosemary by replicating their natural soil, much easier in pots rather than amending garden soil.
It is always better to add too much sand or grit to the potting mix rather than not enough as sand promotes good drainage to mitigate the risk of root rot.
The potting mix should be at least 30% sand or grit to 70% compost by volume of the pot. In climates of high rainfall, as much as 50% sand can be required to ensure the right level of drainage to counteract the increased dampness.
When repotting you should always check the roots for signs of root rot (mushy texture, rotten, dark brown appearance with a bad smell) and snip off the diseased roots with pruners as described above to overwatered rosemary.
If there is significant root rot then it can be too difficult to save the plant, however, you can take a cutting of the stem if there are any remaining healthy branches and attempt to propagate the rosemary.
However, it is often it is better to buy a new plant and pot it up with lots of sand to recreate the rosemary’s preferred Mediterranean soil conditions to prevent the problem in the future.
(Read my article, best potting soil for rosemary).
3. Not Enough Sunlight
In their native Mediterranean hilly range in North West Spain and Portugal, rosemary lives in open and exposed areas where they enjoy full sun all day.
I must stress that you do not need a Mediterranean climate to grow rosemary (they are hardy to USDA zone 6) but you must ensure that they are in the sunniest location in your garden.
The more sun your rosemary receives is correlated with the concentration of essential oils in the leaves which is responsible for rosemary’s distinctive aroma and flavor.
Rosemary requires full sun which means 6 hours of direct sun per day during Spring and Summer to stay healthy. With fewer hours of sunlight the rosemary’s leaves have a less pronounced aroma, turn brown display fewer flowers, and die back.
More sunlight also increases evaporation from the soil around and lowers humidity to reduce the risk of fungal diseases such as root rot.
The Solution...
If your rosemary has poor growth, and aroma with leaves turning brown and no flowers in the Summer then it is important to move your rosemary to a sunnier area of the garden (Read my article Why is my rosemary not flowering?)
Ideally, you have a potted rosemary which makes it much easier to transport to the new sunnier location even if you have to move the rosemary to the front of your house to find the extra hours of sunlight, with at least 6 hours of sun per day.
If the rosemary is planted in a garden boarder or raised bed then it is important to transplant it to either a sunnier area or to a pot as a matter of urgency.
Rosemary is hardy and can be transplanted at any time of year but the best times are Spring and Fall so they do not have to contend with Summer sun and high temperatures whilst they get established.
It is possible to transplant rosemary in Winter but is best avoided as this can also make the plant vulnerable to root rot, however, I recommend transplanting at any time of the year if the rosemary is in too much shade and dying back.
Replant the rosemary in a sunny spot, 2-3 feet away from other plants in soil that has been amended with horticultural sand or grit for improved drainage (and to emulate the soil conditions of the rosemary’s native environment.
4. Soil is Too Acidic (Rosemary Prefers Soil pH 6-7.5)
Rosemary can grow in mildly acidic soil, pH neutral, and alkaline soils, however, it grows best in soils from pH 6-7.5.
Rosemary has specifically adapted to growing on the calcareous soils on the hillsides of Western Mediterranean Europe, and whilst it can tolerate some acidity does not grow well in rich acidic soils.
If your garden soil is more acidic then pH 6 then the rosemary may not live for as long or achieve is potential in terms of growth, fragrance and culinary taste of the leaves as certain nutrients become insoluble due to soil acidity which makes it more difficult for the rosemary’s roots to uptake the nutrients they require.
Most garden soils are pH neutral or either slightly acidic as this is the pH level that organic plant material typically reaches when it is fully decomposed, therefore it will be suitable for growing rosemary and other Mediterranean herbs from a soil pH perspective.
However, some garden soils are naturally very acidic, which could be the reason why your rosemary is dying.
If you are unsure of your garden soil’s pH level then I recommend you purchase an inexpensive soil test kit from Amazon which is very easy to use and available for a great price!
If you find that the soil is too acidic then you will need to transplant your rosemary to prevent it from dying.
The solution.
If your soil is too acidic from growing rosemary then it is important to transplant your rosemary to a pot with new potting soil (use 70% potting soil or multi-purpose compost to 30% sand or grit for drainage).
Transplant the rosemary by gently levering the plant with a garden fork to avoid cutting through roots and slowly persuade the plant out of the ground rather than pulling it out with force.
Replant your rosemary in a pot that is at least 12 inches across and at a proportionate depth to ensure the roots have enough room to establish and to insulate the temperature-sensitive roots from cold weather.
Rosemary grows exceptionally well in pot due to the favorable drainage conditions and because you can customize the oil mix to suit and emulate their native environment by adding lots of sand or grit.
The rosemary should show signs of recovery over the next few weeks if in Spring or Summer or over the next few months if in Fall or Winter as the plant may be dormant.
It is possible to use soil amendments so that your garden soil is not as acidic but it is always much easier and less expensive to replant the rosemary in pots rather than try to adjust your soil.
(Read my article, how to care for rosemary in pots).
5. Wrong Climate for Rosemary
Rosemary originates in the Mediterranean region of Europe where they grow in full sun, warm temperatures in Spring and Summer with mild temperatures in Winter, and with little rainfall.
Rosemary is generally considered a half-hardy plant and can survive some light frost but really benefits from protection from the worst of the Winter weather as severe frost is often a cause of rosemary dying.
Varieties such as ‘Arp’, ‘Hill Hardy’, and ‘Salem’ are somewhat better at tolerating cooler conditions being hardy to USDA zone 6.
However in a cold Winter with a pronounced frost the rosemary can often die back due to both frost damage and cold damp soil which promotes the conditions for root rot and is completely contrary to the rosemary’s preferred mild and dryer Mediterranean conditions
The roots of the rosemary are the most cold-sensitive part of the plant.
In their native environment, the roots can be well insulated by the soil from cold spells.
However, smaller pots also contain less soil which provides less insulation for the cold-sensitive roots increasing the risk of frost killing the rosemary.
But there are some solutions to avoid this…
The solution...
If you live in a climate that regularly experiences frosts in Winter then the best option is to grow your rosemary in pots and either bring them indoors over Winter (and place it in a sunny window or greenhouse) or use horticultural fleece to wrap around the plant, including the pot to prevent damage from lighter frosts.
Always plant your rosemary in a pot that is at least 12 inches across because a larger pot can contain more soil which acts as insulation for the cold-sensitive roots.
It is also a good idea to propagate rosemary from cuttings in the Summer.
This is exceptionally easy and the propagated cuttings often have a high success rate which is improved with hormone-rooting powder and placed in a sunny window over Winter.
This can provide a good supply of free new rosemary plants as an insurance policy if your main rosemary plant dies in the frost.
Read my article for a clear step-by-step guide on the best method for how to propagate rosemary from cuttings:
6. Conditions Too Humid for Rosemary
Rosemary is native to the Mediterranean where conditions are hot but most often relatively dry.
Humid climates with a slow rate of evaporation from the soil are not ideal for rosemary as often the soil or moisture around the plants persists for too long which can promote the conditions for fungal disease pathogens to thrive that cause root rot.
Rosemary that live in overly humid climates tend to show similar signs of stress to rosemary plants that are overwatered or in slow-draining soil with brown or yellow, drooping foliage and a dying appearance.
As rosemary is most commonly found near the coast on hillsides it prefers open areas with good airflow and tolerates some sea spray. If you make some adjustments to the growing conditions, rosemary can cope with some humidity.
The solution.
For rosemary or any other Mediterranean herb to cope with humidity, they must be planted around 3 feet apart from other plants, in an open area.
The more exposed the location with good airflow the better for the rosemary.
Plant rosemary in pots in humid areas is a great way to optimally locate the plant in the windiest area of your garden and you are effectively lifting them up out of the soil in pots which helps to minimize moisture around the plant.
It should be emphasized that well-draining soil and infrequent watering are even more important for rosemary in humid climates. I would recommend as much as 50% sand or grit to 50% potting soil for rosemary in humid climates to reduce the risk of root rot.
A great tip that I picked up from commercial lavender growers (which require very similar conditions to rosemary) is to use a white stone mulch (available from garden centers) to surround your plant, even if it is just in the pot as this can help reflect more light back onto your rosemary which increases photosynthesis, and potentially increase the concentration of essential oils in the leaves of your rosemary for a better aroma and taste.
A white stone mulch also helps to reflect light to ultimately increase temperature and evaporation of moisture and reduces humidity around the rosemary and create a dryer micro-climate to emulate the dryer conditions of the Mediterrenean environment.
With a few careful adjustments to change the growing conditions, rosemary can grow well in humid climates.
7. Heavy Pruning Can Kill Rosemary
The most important rule for pruning rosemary is to only cut back into softer, flexible stems and do not cut back into old woody growth. The old woody growth does not rejuvenate or grow new stems after being cut back, so aggressive pruning prevents new rosemary stems from growing, causing it to die back.
The solution...
Pruning your rosemary every year is essential to maintain its shape and to encourage new growth which has the best flavor for cooking.
Only cut the rosemary back by around 1/3 in the Spring or the Fall ideally a month before the first frost to give the plant a chance to recover from any wounds before Winter.
Rosemary also only flowers on new seasons growth, so if you are trying to encourage flowers and live in a climate with a mild Winter then pruning rosemary in the Fall is often the best option as late Spring pruning can delay or even prevent flowering.
In colder climates with frost during Winter pruning rosemary in Spring is better than pruning in the fall as pruning in the Fall can help to stimulate new tender growth which is much more vulnerable to cold temperatures.
Pruning also makes rosemary less susceptible to Winter damage by maintaining its shape which prevents the old wood from breaking in Winter storms.
Exactly how to prune rosemary is always explained best with a visual guide, so check out this YouTube video for a clear explanation:
8. Too much Fertilizer Causes Rosemary to Turn Yellow
If your rosemary is drooping and perhaps the leaves have turned yellow then this can indicate excess nitrogen in the soil because of using fertilizer either directly or from runoff from lawn fertilizer.
Rosemary is a plant that thrives more on neglect rather than conscientious treatment and actually produces leaves that with a stronger fragrance and more pronounced taste in soil that is medium to low in fertility.
The soil in the rosemary’s native Mediterranean environment is relatively poor, sand and gritty and it is these soil conditions that rosemary grows best and produces the best leaves for cooking.
Too much nitrogen in the soil promotes foliage growth but lowers the concentration of essential oils in the leaves which are responsible for the aroma and flavor of rosemary and reduces flowering.
Too much nitrogen also causes the growth to be weak and droop down which makes the plant more vulnerable to aphid infestations and disease which causes the rosemary to die back.
Established rosemary plants do not require any additional fertilizer as this is in contrast to the sandy soil conditions to which they are adapted.
The solution.
If you haven’t added any fertilizer and the rosemary is yellow and drooping then the soil may be too high in nutrients for rosemary.
The solution to this is to stop apply any fertilizer and ideally to repot your rosemary with new potting soil that is at least 30% sand or grit to 70% potting soil or multipurpose compost.
It is worth emphasizing that rosemary has adapted to growing on hillsides in gritty sandy soils with low to medium fertility soil so by adding sand to the potting mix you are mimicking the rosemary native soil.
Sand does not contribute any significant nutrients to the soil which will counteract soil that is naturally high in nitrogen and improve drainage.
Prune back any excess drooping growth in the Spring and Summer and the rosemary should recover very well in the next few weeks.
Key Takeaways:
- Rosemary turns brown and dies back because of root rot which is caused by overwatering and slow draining soils. Rosemary is a drought-resistant plant that requires well-draining sandy soil. Too much moisture around the roots is the most common reason for rosemary plants turning brown and dying.
- Rosemary requires 6 hours of sun per day to stay healthy. Rosemary in too much shade grows leggy and the leaves turn yellow with a dying appearance.
- Rosemary responds best to a light pruning of 1/3 of the top growth. Avoid cutting back into old wood as this does not rejuvenate and can kill the rosemary. Always trim the softer flexible stems with visible growth to stimulate the growth of more shoots and leaves.
- Rosemary can tolerate a light frost but often dies back in Winter in temperatures below 23°F (-5°C). Rosemary is adapted to mild Mediterranean Winter temperatures. Bring rosemary indoors in climates with cold Winters to protect it from dying from frost and disease.
- To save dying rosemary, snip back any diseased roots that are soft, mushy with a rotten appearance and bad smell, and back to healthy growth with a sterile pair of pruners. Re-pot the rosemary in new soil that is 30% sand or grit to 70% potting soil to replicate the soil conditions of the rosemary’s native Mediterranean range.