Lavender Diseases – There Really are Some!

I read an article the other day which claimed that lavender is immune to disease, a quality that is linked to its healing properties. I’m the first to hop in a bath infused with lavender when I need a break and I am certain that the relaxation it gives me is good for my mental health if nothing else. I also know that many people benefit from using it in other ways, but I feel moved to set the record straight. In the everyday running of our nursery, we are always on the lookout for signs of disease on our plants. They are packed in pretty tight and one rotten apple, so to speak, could easily cause us to lose a lot of stock.

Now, it is true that I have never seen any of the two diseases described below on our lavender or anyone else’s, so I am certain that it is a very disease resistant plant and I am not trying to warn the world of impending lavender catastrophe. Nevertheless, you may come across these invaders in your travels and even
prevent disaster by raising the alarm. Here are the things that we check on to be sure that our plants are healthy:

Alfa Mosaic Virus: This one is quite easy to spot. The leaves will begin to turn yellow in patches and then curl up into contorted shapes. This virus can be spread by both insects and your hands, so it is important to whip out infected plants quickly, using something disposable like a sheet of newspaper to hold the plant. As with any diseased plant material, the best thing to do is burn it. If you really have nowhere to make a fire, bag them up tightly and put them in the bin.

Lavender Shab Disease – Phomopsis lavandula: This is a fungus that kills the stems of the lavender. The clearest sign of it is when all the shoots wilt suddenly, even though there has been no drought. There was a lavender shab epidemic about 40 years ago that killed vast amounts of commercially grown lavender (where the wind could easily spread fungal spores along the rows of plants) and although it seems to have since disappeared, anyone who grows, sells or maintains large amounts of lavender is on the lookout for this microscopic killer. Close inspection of the affected plants (you may need a magnifying glass) will reveal very small black shapes called pycnidia emerging from the bark. If you saw them under a powerful microscope, you would see that they are cup shaped and full of spores. Again, do your best to try and burn the affected plants.

Wet Feet: This isn’t a disease but it spells a far greater hazard for lavender plants than the other two put together. This is the thing that we check every lavender plant for before it gets sent to its new home. If the soil around lavender’s roots is too wet, especially over winter, rot sets in and the bark begins to die. It will be easy to pull the bark away from the base of the main stem and the stem itself may simply twist off from the roots with very little force. Larger plants can struggle on for a little while like this but really they are dead already (and just haven’t realised it).

The chances of coming across Shab or Alfa Mosaic Virus are pretty slim and my bet is that you will never have a problem with them. But if you have any lavender woes, please let us know and we’d be happy to give our opinion. Anyway start with healthy stock, like our lavender plants, ideally planted in April or early May and you should be fine.

Relax, enjoy and watch your garden grow!

24 thoughts on “Lavender Diseases – There Really are Some!

  1. have approx. 50 3 year old french lavender plants that have died. they appear to have a geyish foliage. the plants flowered but the problem started during the summer of 08 with some plants showing signs of failure. this year new growth is very sparse and non existant on most plants ???????? help.
    will obviously have to remove the lot but would like to know possible cause.

  2. I’m sorry to hear about that. Am I right in assuming that the plants had been in the ground for about 2 years in the summer of 2008? If so, they would have been well established and the overwhelming probability is that the drainage of the soil where they are planted isn’t to their liking. Check the plants for soft, loose bark as described above and try twisting a few of the worse looking specimens – it will be pretty obvious if they have begun to rot from the roots up.

    Lavender loves poor soil because it tends to drain so well. Heavier, more fertile soils trap more moisture and can be too damp for lavender. If that is the problem, the solution is to build a mound or ridge by digging in lots of sand, grit and bark mulch until the level of the soil is raised by about 15-20 cms (digging a trench and filling the bottom with stones is usually counterproductive, especially if you have lots of clay in your soil.)

    Lavandins (Lavandula x intermedia) are slightly better at coping with damp than other varities – we will be selling them later this year.

    If that doesn’t sound like the problem, please send us more details!

  3. 2 years ago I moved into a house with a lavender border enclosed on two sides by planks but free draining underneath. Last year a horrible white fungus like melted plastic appeared on a number of plants at root level and the plants died. I disposed of them but this year when I went to replace them, I found several others affected. It seems to be in the roots. I don’t know what to do.

  4. Bonnie, we have the same problem. Last year we’ve planted 12 bushes, they grew very well. This year one of them has a strange white fungus on stems and I don’t know what to do.

  5. Hello,

    I live in Rhode Island and my 4 feet in diameter 3 year old lavender is getting that wilty look at the flower and showing only a few buds…leaves have some sort of spot but it is not a dark spot…yellowish grayish. I have about 7 old and new lavenders around it…Ugh…do I have to remove it? and can I spray something on the others? This is a large variety of French lavender. I am sad.

  6. Hi Bonnie and Iryna,

    Firstly, there is no guarantee that you both have the same problem – just about every fungus begins making its way in the world as a mass of white fibres called the Mycelium and most of them fit the description of “melted plastic” (or “strange”, for that matter).

    If it is affecting the roots, then there are spores or dormant fungus colonies in the soil and they will continue to re-infect any susceptible plant that you put there. There really is no way of telling what it is – even an expert would probably need to do tests in a lab.

    I hate to let you down, but I am afraid that soil fungi are not our area of expertise. When we have had fungi goings ons in our garden in the past, we have resorted to digging out about a metre of soil and replacing it. Then again, we do live in a honey fungus area, so we are quite paranoid about this sort of thing.

    The best thing that you can do is to find someone who knows about fungi to come and take a close look – even if you sent us a good photo, I doubt that we would be able to identify the culprit.

    Failing that, pull all the plants out, replace a reasonable amount of soil and plant something else – I wish there was an easier option but if there is, we don’t know of it.

    Be brave – my grandfather said that if something wouldn’t grow in his garden then it wasn’t going to be invited back.

  7. Hi Gloria,

    I know, it can be rough to have to deal with a sick plant – if only we could put them in bed for a week!

    Before I jump to any conclusions, what has the rain been like where you are? Has the ground been either very wet or very dry? Have you been watering the plants every day (a common mistake with lavender – if it is dry out, a good drink once a week or so is best)? Do you trim your lavender after it flowers (this encourages good flower production)?

    Since you say that you have other lavender plants around it, it does seem unlikely that this one got too wet/dry without the others having similar symptoms. Still, I have to ask.

    Alfa Mosaic Virus causes very distinctive, curled up, contorted leaves with spreading yellow patches. On the one hand, this disease is very rare (in the UK at least…). On the other hand, it is fatal and quite contagious, so you really want to get the plant out of there and on the fire if you think that you do indeed have it – if it comes to that, don’t touch the surrounding plants until you have cleaned your hands well.

    Get back to me with as much detail as you can.

  8. Hello,
    I have several lavender plants in my garden (varying ages, from 1 to 4 years) in Medford, Oregon, USA, and some of them are exhibiting a wilting of the flower stem, about 3 – 4 inches from the top, and then the stem above that point dies and the budding flower with it. The growth of the whole plant is vigorous and full, but when the buds appear, some parts of the plant wilt, as described. I have checked the bark for any black shapes, but there are none. We have clay soil, which I amended well with compost before planting.
    This started with one plant in summer, ’08, and now other plants, not adjacent to the first one, are showing the same signs. Any suggestions? Many thanks.

  9. Hi Marianne

    I would guess that the dying stems are being caused by a fungus called verticillium. While it can affect whole plants it more usually is seen in individual branches or stems (a symptom known as inconsistent wilting).

    Verticillium is soil borne, and travels from the roots up through the plants vascular system. To protect itself lavender (and other plants attacked by verticillium) block off their water passages in an attempt to stop the fungus spreading. No water = wilting/death of bits of the plant.

    Unfortunately, if it is verticillium, then you have a bit of a problem. You can’t cure the plants – they are best removed and burned. AND the disease remains in the soil for a fair while (3-4 years) after the host plants have been destroyed. You can try to be less drastic and just prune out and destroy infected bits. Always disinfect your secateurs in between EACH cut by wiping the blades with a rag soaked in surgical spirit, Jeyes Fluid, Dettol or another strong disinfectant (not bleach). Then feed the plants with a general purpose fertiliser and hope…

    Fungal infections are easily spread so carefully clean boots and tools when you have finished…

    Good luck

    Julian

  10. Hi,

    I have a whole row of lavender and recently noticed that one plant is dying with the bottom stems and leaves turning grey and drying up. I have just checked the rest and when inspecting closely at the bottom some of the leaves are turning grey to. Do you know what this might be? Is this perhaps also verticillium?

    Many thanks

    Gitta

  11. I bought 4 2 gallon lavenders (from someone else I hasten to add). I transferred them to a planter and watered deeply. One of them had signs of wilt (flower stems look and feel limp and the “rabbit ears” on the flowers are down, not upright). I watered and the plant seems to recover, with the flower stems feeling more rigid. The next 2 days, they appear limp again and recover after a watering. The other three plants however are okay and do not wilt even after after days without water. Did I just get a bad plant? or has the plant not settled yet.

  12. Hi! I’ve tried to grow French lavender twice and both time the leaves have developed unsightly yellow spots/blisters.

    I can’t find anything to tell me what this might me!

    Any help appreciated!

  13. I bought 12 lavendar plants from Lowes and, within a month of planting, they have all turned black. I am sure I did not overwater. Do I need to dig out the mulch and dirt, in addition to removing all the plants? Is there not some kind of treatment I could put down and miz into the soil to kill the fungus or bacteria? The area where I planted these lavendar is about 6 ft X 20 ft. and the only other thing I had planted is 3 parsonii junipers.

  14. This info is so good, im sitting in my highshool hort. class, my friend owns about 1000 lavender plants and makes it into oil each year, THIS IS SO INTERRESTING

  15. Hi have had some very heavy rain in the last few weeks (every day). Noticed my 1 year old lavender bushes have turned black. have got some green shoots on one. Do I remove them or do I try to save them? Al

  16. Definitely too soon to give up on your lavender plants. While it may be disease, the black is more likely to be frost damage to young, tender leaves. You will remember we have some quite hard frosts in March and early April and it takes time for the damage to show. If it is they will grow out of it over the next 4-5 weeks and then should be fine.

    Good luck

  17. My daughter has a beautiful huge hedge of Lavender…looks like we are in Provence…two of the plants in the middle of the hedge are dying. Wilting, browning stems and cob webs. Do you have any idea what could be going on? The plants are several years old, about 2′ high X 2′ wide. Please help!

  18. Hedging of lavender does not live for ever. Depending on conditions 5-8 years is a pretty good estimayte. You do not say how old the hedging is so it could simply be old age. Otherwise I would be inclined to put it down to drainage being wors e there than along the rest of the hedge and they have drowned.

  19. I recently brought a young plant in for the winter and it has contracted small red spots on some of the leaves. I did find a small spiderweb but it was removed and hasn’t turned up again for weeks. I’m not sure if it’s important but other plants near the lavender got whitish spots on the leaves. I took them away several weeks ago. I’m not sure but it doesn’t look like fungus. I’m wondering if maybe a bug laid something or. . . Any insight is appreciated.

  20. Hi, I bought a potted lavender plant/bush for half price, half of the plant was wilting, I thought because it needed watering,took it home and put in my unheated greenhouse,noticed when I trimmed the wilted part back that one of the woody stems was split and an orange colour. it is a butterfly type lavender. Could it have been too wet?

  21. Almost certainly. Unfortunately this is probably a good example of “you pays your money, you takes your choice”. Plants are generally sold cheaply for a very good reason. Lavender that has not been looked after while in a pot can develope a number of conditions, especially the showier “butterfly” lavender which can be very sensitive to moisture and temperature. Next time try something a bit tougher like Hidcote Lavender.

    Good luck

  22. I am assuming this is a lavender query. One of the reasons we don’t sell lavender in the winter (and why it is not a good idea to buy it then) is that pot grown lavender can easily be diseased then. The best thing to do is to email a photo and your query to support(at)ashridgetrees.co.uk

    Best

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