Lavender can turn gray because of frost damage or as a result of a fungal disease, caused by overwatering or slow-draining soils. Usually, the fungus Botrytis spp is responsible for lavender leaves turning gray although there are a few pathogens that may cause lavenders to turn gray.
Fortunately, the treatments and the best practices for preventing the various fungal diseases that may cause lavender to turn gray are the same.
It is worth noting that there are many different lavender varieties, and lavender leaves range from dark green to a silvery, almost gray color, so your lavender may well be okay.
Keep reading to find out if it is frost damage that’s causing your lavender leaves to turn gray or fungal disease and how to save your lavender…
Fungal Disease Causing Lavender to Turn Gray
The fungal disease Botrytis spp is the most common cause of lavender leaves turning gray and this typically happens to foliage near the base of the plant.
Lavenders of all species originate in the dry and breezy coastal conditions of the Mediterranean in Europe where they are accustomed to well-draining, sandy soils, with low to medium soil nutrients.
It is in these conditions that lavender grows its best and remains disease-free. So to grow lavender successfully, gardeners should try to recreate these soil conditions to prevent fungal diseases that turn lavender gray.
Fungal diseases are promoted in the following conditions:
| Reasons Lavender Turning Gray: | Causes of Fungal Diseases: |
|---|---|
| Slow-draining soils: | Lavenders require the soil to be well-draining so that it dries out between bouts of watering. If the soil is slow draining (such as clay soils) the lavender roots will be in damp soils which increases the chance of fungal diseases. |
| Areas of high humidity with little airflow: | Lavenders are adapted to breezy coastal conditions and prefer some airflow between the foliage which reduces the risk of fungal diseases. Lavenders should be planted 2-3 feet away from other plants to allow for enough airflow. |
| Over watering lavenders: | Lavenders are drought-resistant plants that prefer dry conditions. More damage is done from overwatering lavenders rather than underwatering. Established lavenders only require watering in hot weather and potted lavenders in most climates require watering once every 2 weeks if there has been little rainfall. |
| The wrong type of pot for growing lavender: | Lavenders require pots that are 12-16 inches across (to be large enough for their root system) and it is imperative that the pot has drainage holes in the base. Do not use a drip tray as this will catch the water and the soil will be damp which promotes the conditions for fungal disease that turns lavender gray. (For more information read my article on choosing the right pot for lavenders). |
How to Treat Lavender with Gray Foliage
The treatment for lavender with fungus is generally the same. If you treat the lavender in time there is a good chance that it will recover from the fungal disease that caused the gray foliage and the lavender should grow normally next year.
- The first step is to remove the lavender from the ground or pot and inspect the roots for signs of fungal infection. If the roots look rotten, then snip away any infected roots with a sterile pair of pruners. Sterilize the pruners with alcohol disinfectant after each cut to prevent the fungus from spreading.
- Snip off any gray lavender leaves or stems carefully and throw them away or burn them to prevent the fungus from spreading around the garden.
- Discard the potting soil, as this will contain the fungus which can spread to other plants. Treat garden soil with an organic fungicide to kill any fungus in the soil where your lavender was planted and do not plant any other plants in the same location for some time.
- Replant the lavender in new soil in a pot so that you can control the soil’s characteristics and contain any potential infections.
- Amend the potting soil with around 1 third horticultural sand or grit and 2 thirds potting soil or compost. (Read my article to learn how to create the optimal soil mix for lavenders). This will replicate the lavender’s preferred sandy soils in its native range and increase drainage as well as provide the right nutrient balance for lavenders as lavender prefers low to medium nutrient soils.
- Once the lavender is planted in the new pot, shelter it from rainfall and do not water for 2 weeks if the roots show signs of rot.
- Place the lavender in full sun and water every two weeks until Fall.
Lavender does often recover from botrytis spp and other diseases that cause it to turn gray when treated so don’t be alarmed.
Note that fungicides are useful for killing the fungus in the soil but if the lavender is already infected with the fungus, the fungicide will not cure the lavender.
It is still necessary to snip away any diseased parts of the plant to give the lavender the best chance of recovery.
Ensure that lavenders are planted 2-3 feet away from each other to allow for some airflow. The more humid or still the conditions, the more necessary it is to plant lavenders a good distance away from each other to prevent fungal disease.
Do not use any moisture-retaining mulch (such as leaf mold) around the lavender and clear away any dead leaves or organic matter from around the plant so that the soil has a chance to dry out and the roots stay healthy.
Avoid overly nutrient rich soils, soil amendments such as manure, or the use of fertilizer. Lavender prefers low to medium nutrient soil. If there is too much nitrogen in the soil the lavender will grow leggy with lots of foliage that is more susceptible to fungal disease.
Always amend the soil with sand or grit before planting lavender to allow for good drainage and to create the soil conditions that lavenders prefer. Lavender thrives on neglect and remains their healthiest, strongest smelling, and display most flowers in harsh, dry conditions.
Water lavenders at the base of the plant rather than overhead to reduce the amount of time foliage is damp which would promote the conditions for fungal disease.
(For more information, read my article, how often to water lavender).
Always plant lavender in full sun for a healthy, disease-resistant plant with a strong fragrance and a good display of flowers.
(To check the moisture of your soil around the roots of your lavender plant to ensure the soil is not too damp, try using an inexpensive soil gauge which also measures the soil pH and intensity of sunlight. This soil gauge is easy to use and available for a great price on Amazon!)
Frost Damage Causing Gray Foliage
It is possible that lavender foliage looks gray or brown due to frost damage or it may be just last year’s growth that requires pruning. English lavenders are cold–hardy and will survive cold winters with snow, frost, ice, and freezing temperatures.
Avoid Spanish, French, and Portuguese lavenders as they are not cold hardy and often suffer in climates with cold Winters.
Prune lavenders in the Spring to stimulate new growth (which promotes flowers) and increase the lavender longevity.
Here is a useful YouTube video that shows what last year’s grey foliage looked like in the Spring and how to prune it back effectively:
(For all the best care practices, read my article, on how to grow lavenders in pots).