Lavender plants are generally pretty hardy, so it can be concerning when they start to turn yellow and look like they aren’t doing well.
Luckily, it’s pretty simple to identify what is wrong with your plants and what needs to be done to fix them.
The most common causes for lavender turning yellow are overwatering and too much nitrogen in the soil. If the soil around your lavender plant stays moist too long it can start to kill your lavender plant, and you’ll notice the leaves turning yellow and brown and wilting.
Another potential cause is a viral infection – such as alfalfa mosaic virus or tobacco mosaic virus.
Let’s discuss what could be wrong with your plant in a bit more detail.
Problem: Too Much Water
Probably the most common issue with lavender plants is the soil staying moist too long, causing the plant to start to develop root rot.
When this happens, you’ll notice the plant starting to wilt and turn yellow followed by turning brown. You’ll especially notice the bottoms of the stems turning brown after root rot starts to take hold. If you’re growing in a pot, you’ll notice the roots turning a mushy brown color when you pull it out of the pot.
This happens for two main reasons:
- Overwatering – Lavender doesn’t need a lot of water – being native to an area with dry, sandy soils – so if you have a mature lavender plant, you shouldn’t water it more than once every two weeks.
- Bad Soil – If you have a heavy clay soil (or soil that has so much organic matter that it holds onto water and stays moist for weeks), this will prevent proper drainage and leave your lavender plant standing in water any time it rains.
If the problem is just that you’re watering too frequently, the solution is just to water less often.
If you’ve been having heavy rains lately, that could be a cause of the issue as well, especially if you have one of the soil types described above.
In this case, you may want to try ammending your soil with a bit of compost to improve drainage around your plant. In clay soils, this still may not completely fix the issue, as the soil below what you’ve ammended will still have drainage issues.
If you’ve ammended the soil and it still hasn’t fixed the issue, try moving your lavender over to a raised bed.
Building a raised bed to move your plants over to and filling it with sand will greatly improve the drainage around your lavender and will allow water to run off along the surface of the ground.
If you need more information, check out my guide on how to grow lavender.
Problem: Too Much Nitrogen
Another reason why your lavender may be turning yellow – especially on the lower leaves – is that you have too much nitrogen in the soil.
This can especially be the case if you’ve recently spread fertilizer or ammended the soil with manure or compost.
If this is the issue, you may also notice your plant may not flower (as heavily or at all) and may start growing sideways (or outwards instead of up).
In this case, unless you notice serious negative effects on your plant, you don’t necessarily have to do anything. If you’ve spread granular fertilizer, you can try removing some of it, but it will eventually work itself out.
Problem: Mosaic Virus
If the yellowing on your leaves looks more like a mottled, almost geometric pattern, the issue may be a viral infection from one of the types of mosaic virus.
If your plant gets this virus it basically has to be removed and disposed of in a way that minimizes any contact with surrounding plants, so if you think this may be what your plant has, you may want to take a cutting down to your local extension office for a positive diagnosis.
Note: This virus is extremely easy to spread. If you think your plant may have this virus:
- Avoid touching the plant with your clothes or shoes. Change and wash your clothes afterwards.
- Either burn or bag and throw away the affected plant with your garbage. Do not throw it away with your yard waste.
- Sanitize any tools that touched the plant afterwards using bleach.
I don’t believe either of the mosaic viruses kill lavender plants entirely, but they do harm the plants and reduce their productivity.
You can still harvest and use lavender flowers from plants with mosaic virus for distillation, satchels, soaps, and in baking. The virus isn’t harmful to humans or animals in any way.
I don’t have a picture of this virus on a lavender plant, but here is a photo of a zucchini leaf so you know what to look for.
There are 3 main reasons why lavender plants will start to yellow – some worse than others. When considering why your plant is starting to turn yellow, consider whether anything has changed recently.
For example, has it been raining heavily recently? Did you recently fertilize your plants or spread compost?
If you can come up with anything, that’s the best place to start when trying to identify the issue. If not, start paying attention to your soil (especially after rain) to see how long it stays wet. If your soil isn’t drying out quickly, that could be the cause of your issue as well.