Why is my Lavender Turning Black?

The two main reasons for lavenders turning black are fungal or frost damage. pathogens like Fusarium Verticillium or wilt. The lavenders may turn dark at their base on the foliage and stems, and as spots of black on the leaves, as is typical of this disease. Septoria leaves spot.

Fungal diseases are more prevalent in moist soils and environments with high humidity.

There are a variety of fungal pathogens that change the color of lavender into black. It is difficult to determine the fungus that is responsible for the condition.

But, the strategies to prevent and treat are the same, and you should continue reading to find the reasons behind this, and the best way to save the lavenders that are becoming into black…

Lavenders turning Black because of Frost damage

One of the most frequent causes of lavender turning black is because of damage from frost.

It is more prevalent in French and Spanish lavenders since they have less tender leaves than the English and hybrid varieties that are more hardy to cold and are able to withstand frost, ice and snow however they may be vulnerable to damage caused by an early frost.

The late frosts of Spring are the most significant cause of caused damage since the newly spring-flowering foliage is more fragile and thus more at risk from freezing temperatures that are sudden and unexpected.

It is possible to tell if your lavender is turning black because of damage from frost rather than fungal disease by observing that the newly emerged Spring foliage is becoming black or brown, whereas the mature foliage is generally unaffected.

The best solution… can be to cut off the foliage that is black and was killed by freezing and frost. This will encourage new growth , and the lavender will recover without issue.

If your lavender is badly damaged by frost, it is likely that the lavender is French, Spanish or Portuguese varieties of lavender that are unsuitable to be kept outside all year long in the climate you live in.

You should instead think about plant English lavender varieties like ‘ Munstead‘ and ‘ Hidcote‘ that can withstand cold temperatures and can last for 15 years or more.

Lavender Turning Black due to Fungus

When the flowers are turning black at the bottom with leaves and stems both affected, or if the leaves have black spots appearing on the foliage then the lavender suffers from a fungal infection instead of frost damage.

There are various pathogens which cause the lavenders to change color from black or brown and often occurs when it is accompanied by an appearance of drooping lavender.

The various pathogens that can cause the lavender to turn black, all flourish in soils which are constantly humid and in areas with greater humidity.

It can be difficult to pinpoint the pathogen responsible for the illness However, the strategies of prevention and methods to address the issue are similar.

two hands in lavender

How to Solve Lavender Turning Black…

If your lavender is turning brown or black, it is best to remove the lavender from the soil. The fungal diseases which turn the lavender black are present in soil, and thrive in moist conditions.

Do not plant any other lavenders, or in particular other plants in this area of your garden since they could also be affected by the fungus.

The treatment of the disease

  • After you have taken the lavender out of the soil, examine the roots. The infected roots appear black or brown and look rotten.
  • Make use of sterile pruners to cut off the affected roots. Make use of a cloth that is immersed in the disinfectant (such in alcohol as a disinfectant) and clean off the cutting blade of your pruner following each cut to ensure that you don’t accidentally transfer the fungus to other roots. Wear gloves and clean your hands regularly because fungal diseases can easily transmitted if you don’t pay attention.
  • After the roots have been cut to ensure that only those that look healthy remain examine the stems and leaves that are left of lavender. Cut off any area of the plant that is becoming black and showing indications of infection. Ensure that you clean the pruners clean after each cut.
  • Take all affected stems, roots and leaves that you’ve removed. You can either dispose of it and burn it in order to stop spread of the disease. Don’t put it in compost because the fungus could be living within the organic matter.

The next step is to plant the lavender again in a well-drained soil in the form of a pot. Don’t replant your lavender on the exact location or in a different area of your garden , to avoid spreading the fungus. Apply an organic fungicide on the soil in order to kill the fungal infection.

  • Plant your lavender into a container, so that you can keep any affected plants and stop the spread of the disease. Pots are also better at draining than the soil in your garden (see my post on selecting the right pot to plant lavenders in).
  • Add 1/3 horticultural sand , gritty and 2/3’s compost or potting soil. This ensures drainage efficiently and also gives the roots the chance to dry after exposure to moist soil. The new soil mix won’t be affected by any fungal diseases and will give your lavender a high chance of recovering.
  • After you’ve replanted your lavender, do not water it again for at least 2 weeks. Since the lavender is inside the pot, I would suggest protecting it from rain for the moment.
  • It is also possible to add an organic fungicide on the soil in the pot to avoid future infection. Be aware that fungicides are only able to be used as preventative measures, therefore if your lavender is already turning black, it is not possible to cure the lavender . It is necessary to cut off the affected areas of lavender before replanting it in fresh pot soil.

How can you prevent fungal diseases…

In their original Mediterranean habitat, lavenders flourish on soils which are well-drained, sandy and medium to low in nutrients, with an alkaline pH. They thrive in full sun , and with minimal rainfall.

To ensure that your lavenders in your garden are healthy, it is essential to reproduce certain conditions of the soil in Southern Europe for them to flourish.

This includes:

  • Lavenders are planted in full sun (more than six hours per day)
  • Making sure the soil is drainage (amend the soil by adding gravel or sand)
  • The lavender should be watered only occasionally and only when absolutely required (established lavenders don’t require irrigation in the majority of climates).
  • Make the soil more nutrient-rich so that it is less to moderate on nutrients and don’t use fertiliser (overly fertile soil can cause lavenders to droop, and more prone to fungal diseases).
  • Make adjustments to the pH of the soil in the event that the soil is too acidic (or transfer it to pots so that you can alter the soil’s characteristics to grow lavender).
  • Find the lavender in the garden in an area that has good airflow. Lavenders don’t like humidity high because they have used to living in the breezy conditions along on the Mediterranean coast. Pots are an effective way to boost the flow of air, and to avoid diseases.
  • Use organic materials like mulch away from lavenders since they help keep soil moist and increase the conditions for fungal diseases.

The planting of lavenders in these conditions is the most effective way to avoid any fungal illness.

(For more details on taking care of lavender, read my articles on lavender, Munstead, Hidcote and Grosso).

Lavender is not a good choice in soils that are heavy, such as clay, or any soil that naturally boggy and drains too slow.

If your garden soil is draining slowly, then I suggest that you plant or transplant your lavender into pots that have much better drainage than the soil in your garden.

It is also possible to amend the soil mix to make pots with much less difficulty than garden soil by adding substances like horticultural grit and sand, which aids in drainage, and balances soil fertility, and mimics the ideal soil conditions for lavenders.

Get rid of any organic matter that has accumulated around the lavender, such as dead leaves that fall in the Fall because this can hold on to moisture at the base of the plant, increasing the likelihood of contracting an infection.

Mulching with white stones can be a great way to control weeds and reflect light back to the foliage of the lavender and reduces the moisture in the surrounding area.

Don’t mulch with substances that hold water, like compost, leaf mould, or well-rotted manure.

The extent to which your lavender is able to recover from turning black because of fungal illness will be contingent on the severity of the disease.

Plants that are mildly infected generally be able to handle treatment, but plants that are severely infected are usually hard to revive, and could be killed.

If the lavender can’t be saved, you can burn it in order to eliminate the fungus, or dispose of it so that it doesn’t spread to your garden.

Prevention is always better than cure when it comes to lavenders, so make sure that the lavender plants are in well-drained, dry soil, using either grit or sand and do not over-water them.

(Read my article about the most effective soil mix for the lavender plant.).

The most frequent problems arise from excessively watering lavenders, and then insufficient watering because of their inherent resistance to drought as well as their need for dry conditions.

All lavenders can be susceptible to disease because of humid soils and humid conditions, but hybrid lavenders are less susceptible to diseases.

( Lavandula x intermedia) “Grosso” is an English lavender that blends the hardy, cold traits of English lavender with the long blooming time of Portuguese lavender. It has an aroma of sweetness.

Hybrid lavenders like “Grosso” are a fantastic option due to their toughness together with English lavenders like ‘Hidcote’ as well as Munstead’.

(For all the most effective ways to care for your plants, check out my article on on how you can plant lavender inside pots).

Key Takeaways

  • The darkening of the lavender typically occur as a consequence of damage caused by frost to the new growth that develops in spring or as a sign of a fungal infection.
  • The fungal disease is more common in moist soils, while lavender thrives in dry, sandy, and well draining soils in order to avoid diseases and remain healthy.
  • The over-watering of lavenders and the planting of lavenders in soil that is rich in nutrients can increase the risk of fungal diseases that affect your lavender.
  • Keep lavenders from turning black by placing them in soil altered with horticultural sand or grit, which helps improve drainage and to improve the fertility of soils in order to restore the characteristics of soils that are typical of the native lavender Mediterranean. Established lavenders do not require irrigation and do not require any water since they are drought-resistant.
  • Take the lavenders out of the soil, then cut off the affected roots, leaves and stems. Replant them in a new, well-draining soil in a pot. protect from rain over the course of two weeks.
  • The lavender plant is not always able to recover from fungal illnesses, however by cutting off the stems, leaves and roots, and then replanting them in the pot, you will ensure that your lavender has the best chance of recovering.
  • Burn the lavender that is contaminated to stop the spread of the fungal infection.
Stephanie

Stephanie

Went from a bad gardener to a half-decent one over 10+ years. Super happy to share my tips and tricks with you :)