The reason for sage plants turning brown is because of the fungal disease root rot which is caused by excess moisture around the roots due to overwatering or slow-draining soils. Persistently damp soil around the roots of the sage results in brown leaves stems and roots with a wilted appearance.
Sage that is turning brown (or yellow) is a sign of stress due to excessively damp soils and not because the sage requires more frequent watering which is a common mistake when growing Mediterranean herbs.
The reason for sage turning brown is most commonly due to:
- Overwatering
- Slow draining soil
- High rainfall
- Humidity
If your sage is planted in a pot or container, ensure the pot has drainage holes in the base for excess water to escape.
Keep reading to learn more about why sage plants turn brown and how to solve it…
Slow Draining Soil (Add Sand or Grit to Improve Drainage)
Sage is a Mediterranean herb that grows natively in sandy soils on hillsides in Southern France where the soil tends to drain very quickly and moisture quickly evaporates in the blazing sunshine.
Sage is a very low-maintenance plant, however, they must be planted in well-draining soil that does not hold onto water to replicate the growing conditions of their native environment.
If sage is planted in rich compost, clay soil, or compacted soil, then water will not drain away from the roots efficiently.
Sage requires soil that is well draining so that the soil around the roots dries out somewhat between bouts of watering.
Slow-draining soils that retain water around the roots of the sage plant, promote the conditions that lead to the fungal disease root rot which turns the sage brown or yellow and can kill it if left untreated and often has a wilting appearance (read my article on why sage plants wilt and how to solve it).
The solution is to:
- Amend the soil with sand or grit to improve the drainage so that it is roughly 20% sand and 80% potting soil.
- Plant or transplant sage in pots that have more favorable drainage conditions compared with garden borders.
Pots are an excellent way to grow sage as you can very easily control the soil profile and the pot can be moved indoors to protect sage from cold weather (sage is not very cold hardy).
Choose a pot that is roughly 16 inches across to ensure that roots have enough space to establish.
To prepare or amend the soil for planting sage, that is turning brown you will need to:
- Dig out a planting area of around 18 inches x 18 inches (or choose a pot of around 16 inches across). If the surrounding soil is slow-draining clay, the more soil you can dig the better for drainage.
- Place the sage in the planting area and backfill the area with at least 20% horticultural sand or grit and 80% compost or potting soil.
- Replant the sage and let it dry out for a few days if the leaves are brown before a generous watering in around a week.
Sage does not always recover from root rot and it depends on how much of the plant has turned brown but re-planting the sage in a well-draining soil mix is key to help it recover.
Overwatering Causes Sage to Turn Brown
Sage is a plant that thrives in the hot and dry region of Southern Europe with infrequent rainfall, and blazing sunshine.
Therefore sage is adapted to a harsh dry environment and when established it is a drought-resistant plant and actually thrives in these conditions, particularly in terms of the aroma of the leaves and the bold taste for cooking.
If you water your sage plant too frequently then there will be persistent moisture around the roots which can lead to root rot and the leaves turning brown.
- Water established sage plants every week when planted in pots with a generous soak during the Spring and Summer if the weather is hot.
- It depends on the specific conditions of your environment but sage planted in garden soil often only requires watering once every two weeks if the weather is hot and with no significant rainfall.
- In climates that are cooler and have higher rainfall than the Mediterranean your sage plant may not require any water at all, (perhaps only in times of drought) attaining all the moisture it requires from the environment.
- Sage does not require any water in the Winter as the plant is in a state of dormancy, unless it is indoors in which case water once every few weeks to avoid the plant drying out completely.
Sage prefers a soak and dry style of watering as this encourages the roots to grow and establish so always water generously but not too frequently to avoid root rot and the leaves turning brown.
Sage prefers dryer soil so more problems occur because of overwatering rather than underwatering.
Scale back the watering and improving the drainage is key for the sage to recover from a brown appearance.
High Rainfall Can Cause Root Rot
Sage grows in a dry climate with infrequent rainfall, however, it is an adaptable plant that can grow in a wide variety of different environments with some adjustments to the conditions.
Sage can grow very well in rainy areas of the Pacific NorthWest in the USA and the UK.
However, in climates with high rainfall, the soil conditions become even more important to avoid root rot and the leaves turning brown by ensuring excess water can drain away from the roots of the sage efficiently.
Sage that outdoors often does not require any additional water in rainy climates so avoid overwatering to keep the plant healthy and to ensure the leaves have a good flavour.
If your sage is turning brown due to high rainfall then there are 2 things you can do:
- Amend the soil with a particularly high amount of sand or grit (up to 50% sand to 50% compost).
- Plant sage in a pot and shelter it from persistent rainfall where possible.
Well-draining soil is important for growing sage but is it crucial for sage grown in rainy climates to avoid root rot.
At up 50% sand as a soil mix may seem excessive but consider that sage grows in very sandy soils on hillsides and thrives in its native environment with fast-draining soil conditions.
Too much sand or grit is always better than not enough when it comes to growing Mediterranean herbs.
Planting in pots and containers is always best in rainy areas as pots have more favorable drainage than garden soil so the roots are not surrounded by damp soil.
If the sage leaves are turning brown then shelter the sage from more rainfall that is forecast as this will compound the root rot problem.
With enough time the soil around the roots can dry and the sage can begin to recover.
Climates with higher levels of Humidity
Sage grows often by the coast so it is able to tolerate some sea mist but the Mediterranean sun often dries any humid conditions throughout the day.
Excess humidity can be a problem for sage plants as the lower rate of evaporation means that the soil around the roots is likely to stay damp for longer.
The solution for growing sage plants in a humid climate is to always plant them in a pot and space roughly 2-3 feet away from each other. This distance allows for airflow around the plants and avoids the microclimate that can happen when many potted plants are in a crowd.
How to Save Brown Sage Plants
If the sage plant is turning significantly brown then the best thing to do is to:
- Trim back any affected foliage and stems with a sterile pair of pruners.
- Use a cloth with disinfectant to wipe the pruners after every snip of the plant to prevent the spread of fungal infection.
- Burn or throw away the affected brown foliage rather than placing it in a compost heap.
- If it is easy enough to take the plant out of the soil, inspect the roots and snip away any that are brown and slimy as these are infected. Be careful to wipe the pruners after each snip.
- Scale back the watering, amend the soil with sand or grit to improve the drainage, shelter the plant from high rainfall, and place pots about 2-3 feet away from each other so the sage can recover.
Alternatively, you can cut some of the healthy grow to use for propagation to save the plant. Propagating sage and other Mediterranean herbs is easy and inexpensive, watch this YouTube video for a good guide:
Key Takeaways:
- Sage plants turn brown because of root rot. The symptoms of root rot are brown leaves, brown stems, and a drooping appearance. The cause of root rot is because of too much moisture around the roots due to overwatering or slow-draining soils.
- High rainfall and humidity can also significantly contribute to the conditions that promote root rot can cause sage leaves to turn brown.
- Ensure that sage is planted in well-draining soil amended with sand or grit, scale back the watering, plant sage in pots or containers in gardens with slow-draining soil or high humidity, and space the pots 2-3 apart to allow for airflow.
- Snip away infected brown foliage with a pair of pruners and allow the soil to dry out around the roots to allow the sage to recover.