Why do Lavender plants turn yellow?
The most common reasons for lavender foliage turning yellow are because of high nitrogen levels in the soil, over watering of lavenders or lavenders that are planted in soil that drains too slowly.
If the lavender has a yellow/brown foliage with a overall drooping or wilting appearance this indicates that the lavender is either over watered or in slow draining soil, not under watered (lavenders are drought resistant).
Lavender foliage that is yellow, and has a leggy appearance with few flowers is suffering from soil that is too high in nitrogen.
Read on to find out exactly why your lavender that is turning yellow and how to resolve it…
Causes of Lavender Turning Yellow: Excessive Nitrogen and Over Fertilizing
One of the most common reasons lavender turns yellow is because of excessive nitrogen in the soil.
Nitrogen is a nutrient that is required by all plants, but too much nitrogen in the soil will result in a lavender that is leggy, untidy in appearance and has foliage that turns yellow.
Lavenders are native to the Mediterranean region of Europe where they naturally thrive in sandy, nutrient poor soils.
To grow healthy lavenders that produce blooms you need to recreate these conditions.
Soil that is too rich needs to be amended with sand or grit and you should avoid using fertilizers on established lavenders. This is counter intuitive, but the more fertile the soil, the more likely you are to have a lavender with yellow foliage and no flowers as lavenders are adapted to low fertility soil and prefer these conditions.
Sand and grit do not contribute much nutrients or nitrogen to the soil so you can offset nutrient rich soils by amending with these materials. Sand and grit will also provide the optimal soil structure, which allows for fast drainage that lavenders require to avoid diseases such as root rot.
Ideally you should amend the soil with sand or grit before planting lavenders in your garden or pots, however you should amend the soil as a matter of urgency if the lavender foliage is turning yellow.
For lavender that are already planted, use a fork to ease the lavender out of the ground, protecting as many roots as possible. The ratio of sand to soil should be around 30% sand to 70 % soil.
(If you have clay soil please read my article on how to prepare clay soil for lavender growing as clay soils require significantly more amending).
As long as you follow the best practices of care, your lavender should recover and produce flowers next season if you adjust the soil and stop using unnecessary fertilizer.
Yellow Lavender: Over Watering
Over watering is perhaps the most common mistake when it comes to caring for lavenders. Lavenders are adapted to the harsh, drought like conditions of a Mediterranean summer and therefore require very little, if any water.
Over watered lavenders have a wilted, drooping appearance and foliage that is either yellow or brown. Most people mistake this wilted appearance as under watering and compound the problem by over watering the lavender further.
- Established outdoor lavenders do not need any additional watering in temperate climates, only in times of notable summer drought. They will attain more then enough water from rainfall.
- Potted lavenders will need some more attention as pots do tend to dry out quicker (see my guide to watering potted lavenders).
- Lavenders in arid climates will generally only need watering once every two weeks in spring and summer.
- Indoor lavenders will only need watering every two weeks (see my guide for indoor lavender watering tips).
- Lavenders will not typically need any water at all during fall and winter, however if you take your potted lavenders indoors over winter then water once every 4-6 weeks will be sufficient (assuming the soil is suitably well draining).
To remedy yellow lavender that has been over watered, the solution is to simply stop watering your lavender for at least three weeks and let the soil and roots dry out. However some lavenders will simply not recover from persistent over watering and they will die, so prevention is better the cure in this case.
Often over watered yellowing lavenders is a problem that is associated with poor draining soils. Both of these factors have to be taken into account when trying to revive a lavender will yellow or brown foliage.
If you are in a rainy, temperate climate then I recommend planting lavenders in pots as they provide better drainage and the pots can be moved under cover or at least to the rain shadow of a building in times of persistent rain.
All lavender species grow very well in pots, see my guide on potted lavender care for some great tips.
Poor Soil Drainage: Yellow/Brown with Drooping Appearance
Lavenders are naturally suited to sandy soils which drains very quickly and doesn’t hold onto moisture for very long, unlike soils with a high organic content.
Yellow (or brown) foliage is a symptom of the disease root rot. Lavenders like the soil to dry out between periods of watering as the roots do not tolerate persistent wet soil.
To successfully grow lavenders you must replicate the soil conditions of their native Mediterranean. The soils where lavender grows naturally, in countries like Spain, Italy and Southern France is very sandy and sometimes gravelly.
This allows water to drain through the soil very quickly so that the roots of the lavender can remain relatively dry and stay healthy.
All you need to do to improve the drainage in your garden soil or pots is to amend the area of planting with sand. In most gardens about 30% sand and 70% soil is a good proportion to aim for. However in particularly slow draining soils, you can increase this to 50:50.
The soil needs to be ideally amended with sand or grit to a depth of around 18 inches as this will accommodate the roots system of the largest lavenders when they reach full maturity.
Till or dig the area to add your sand or grit and then replant the lavender.
Alternatively, if your garden is particularly low lying and naturally has damp soil, then you can transplant your lavenders to pots or create raised beds to recreate the right soil conditions for lavender growing.
If you add the sand grit then you can effectively emulate the ideal Mediterranean growing conditions and the roots of the lavender can dry out properly, which should alleviate the root rot that is turning the foliage of the lavender yellow.
However root rot disease can kill lavender that has been in wet soils for too long, so you may have to replace the lavender plant eventually, but it is worth trying to save it.
High humidity is another factor to consider if your lavender is turning yellow. Lavenders prefer to keep their roots and foliage dry (although they can tolerate coastal conditions).
Lavenders will struggle to thrive and produce blooms in humid climates, but there are a few things you can do to improve their chances:
- It is important that you space your lavenders at least 2-3 feet apart from one another and place them ideally in a place with some air flow. An occasional breeze will help to keep the foliage and soil dry.
- Lavenders need full sun (at least 6 hours per day). The more sun lavenders receive the healthy the plant will be and less likely it will succumb to disease and yellowing.
- A great tip that I got from commercial lavender growers in California is to use white stones, or pebbles as a ground cover. The bright white stones help to reflect sunlight back onto the foliage of the lavender which creates its own micro climate on sunny days. This helps to keep the lavender dry, suppresses weed growth and increases the lavender harvest in terms of oils and blooms.
- Planting lavenders in pots will allow you to place the lavender in the sunniest place and ideally a location that is away from cause of humidity. Placing lavenders on a patio rather then near lots of vegetation will be more favourable for reducing yellowing lavender.
Adding material such as sand or grit to the soil will also help keep the lavenders roots dry which can be a problem in higher humidity areas. Dryer foliage will lead to a healthier plant that is less likely to turn yellow.
- The most common reasons for lavenders turning yellow are; excessive nitrogen in the soil, too much fertilizer, over watering, poor soil drainage or high humidity.
- Over watering, poor soil drainage can be solved by amending the soil with sand or grit with to make a ratio of at least 30% sand to 70% soil. This emulates lavenders native soil conditions in their Mediterranean range. Establish lavenders will only need watering in times of drought.
- Lavenders have adapted to growing in low fertility soil. If soil fertility (particularly nitrogen content) is too high then the lavender will turn yellow and grow leggy, with fewer flowers. Lower the fertility of the soil by adding sand and grit which provide the optimal soil structure and do not contribute much nutrients to the soil, thereby counter balancing higher fertility soils.
- Do not use additional fertilizer for your lavenders. Lavenders that receive fertilizer will turn yellow, grow leggy and unattractive with fewer blooms much like they would in high fertility soils.
- High humidity can contribute to lavenders turning yellow. To reduce the effects of humidity, try growing lavender in pots and space them a generous distance (2-3 feet) from other plants to allow for improved air flow. A white reflective stone grown cover will reflect sunlight back onto the lavender and help to keep the foliage dry and healthy.