Shrub trouble for Foliage Follow-Up


I have shrub trouble (shrubble?). No, this isn’t a picture of it. This is my succulent wall, which is doing beautifully this mild, dry winter, and which simply glows in late afternoon light.


Here’s the “shrubble.” One of my favorite evergreens for shade and deer resistance, Chinese mahonia (Mahonia fortunei) has, for the second winter in a row, developed a bad case of powdery mildew. It looks as if a careless painter has splattered it with white paint.


I’m generally laissez-faire about plant diseases and pests, and last winter when the leaves got all mildewy I did nothing and hoped for the best. And it worked — or seemed to. The problem cleared up by summer.


But now it’s back, and worse than ever. I think I’m going to have to take action. Any suggestions?


Rather than end on a sad foliage note, let’s have another look at the beautiful succulents. No powdery mildew there!

This is my February post for Foliage Follow-Up. Fellow bloggers, what leafy loveliness is going on in your garden this month? Please join me in giving foliage its due on the day after Bloom Day. Leave a link to your post in a comment below. I’d appreciate it if you’ll also link to my post in your own — sharing link love! If you can’t post so soon after Bloom Day, no worries. Just leave your link when you get to it. I look forward to seeing your foliage faves.

_______________________

Upcoming Events and News

Join me for my kick-off garden talk for my new book, The Water-Saving Garden, on February 27, at 10 am, at The Natural Gardener nursery in southwest Austin. My talk is called “Hold the Hose! How to Make Your Garden Water Thrifty and Beautiful,” and it’s free to the public. Afterward I’ll have books available for purchase and will be glad to autograph one for you! Dress for the weather, as the talk will be held in the big tent outside.

Look for me on Instagram as pamdigging. See you there!

All material © 2006-2016 by Pam Penick for Digging. Unauthorized reproduction prohibited.

41 Responses

  1. Saurs says:

    Counterintuitively, powdery mildew (versus downy mildew) thrives in warm, dry conditions (very much like the weather right now!) and more so in shade and where soil is fertile, and spores of most species infecting ornamental foliage can’t survive water-y (or sunny) environments: so the trick is a spray of water, preferably with a surfactant (soap), and at the right time, mid-morning to early afternoon just before air temperatures reach their height. If you’re noticing twisted or gnarled growth, pinch out the infected stems with sterilized tools and, of course, remove leaf litter promptly to dispose of spores. Horticultural oil is a more drastic solution, and I imagine you’d never consider a fungicide, but there are decent, narrow-spectrum options available to folk without PCAs or QALs, although they’re most effective as protectants and when applied much earlier in the season.

    I wouldn’t feel too badly, though–you’ve a very healthy garden, and sometimes one has to chalk up infrequent pest problems to odd weather.

    • Pam/Digging says:

      Thanks for the treatment tips, Saurs. I confess, as someone who rarely thinks to treat anything and spends zero time in the product aisles of garden centers, some of what you mention is a complete mystery to me. What, for example, are PCAs or QALs? And why is horticultural oil considered drastic? I’ve googled all of these and am not getting much info. —Pam

      • Saurs says:

        Oof! Sorry, Pam, for being cryptic. I now suspect I was mistaken, but I was under the impression you were of the minimal-interference school of thought, where even comparatively benign substances are used only as a last resort — neem or other plant-derived oils sometimes falling under this category, a carefully controlled and timed sprinkle of glyphosate to murder patches tenacious warm-season turfgrasses certainly doing so. (I personally practice as intelligent IPM as I can get, but so long as everyone recognizes that all matter is chemicals I wholly respect the organic approach, particularly for ornamentals. Right plant for the right place and climate tends to limit the need for all manner of pesticides, anyway, and good cultural practices like abstaining from highly fertile soil amendments, except in the case of extreme deficiencies, and smart irrigation practices further lessens the need for interference.)

        Now that I think about it, Texas probably doesn’t have pest control advisor (PCA) certifications, much less qualified applicator’s licenses (QAL). Here in California we do, although that doesn’t prevent the boxstores and mass online merchants from selling 2,4-d (or, more to the point, fungicides like mancozeb) to anyone who wants them.

        I try to follow labels closely and read the MSDS prior to purchasing any application new to me, but the local-most cooperative extension and nearby ag colleges are, respectively, my first- and second-best resources when I’ve a question about the safest, simplest solutions, and I’m lucky enough to have a science-based master gardener program nearby (not every county in the US is so lucky, unfortunately). You, on the other hand, have Texas A&M just a stone’s throw away! What a wonderful resource. I’d love to hear what they say about your mahonia, and whether it’s not too late in the season to try to smother out that mildew.

        • Saurs says:

          Also, as you say, summer aridity zaps out that mildew no matter how shady the area, so it really sounds like a freak occurrence two years in the running. I’m biased, though, because that stand of mahonia is just beautiful to me, paint splatters or not.

          Going to plug a few on-line resources for you and your readers. Information certainly isn’t universal, probably most applicable to the US southwest and California:

          UC ANR IPM (integrated pest management) program
          Texas IPM program

        • Pam/Digging says:

          Haha, well, I AM of the minimal-interference school of thought, Saurs, in that I believe in planting what wants to grow where you live (i.e., meeting the local conditions), taking care of plants in the early years, and then adding more of the thriving plants while removing those that fail to thrive. Doing that, as you point out, allows you to rarely have to even think about using chemicals.

          Yes, Texas A&M is a great resource and (for native plants only) so is the Lady Bird Johnson Wildflower Center. Thanks again for all your suggestions! —Pam

  2. catmint says:

    the succulent garden is inspirational, sorry about the mildew. Usually I ignore things like that, too, for as long as I can, if it persists I consider ditching it. But Saurs has a lot of solutions to try before that more extreme response!

    • Pam/Digging says:

      I’d only pull the mahonia as a last-ditch measure. I really love the foliage and size, and there aren’t a lot of evergreen options here in central Texas for shade, deer, and that don’t get enormous. It seems strange that this problem has only occurred the last two winters, out of nine spent in this house. But maybe once it takes hold it’s persistent? —Pam

  3. I think you should rip out that mildewy shrubble and put something there that won’t mildew. It obviously doesn’t like something to do with that area or…ignore it.
    On another line of thought, mine not yours, I think you should paint this block succulent planter much like you did your walls in the garden. It would bring more color to this area and you (I) wouldn’t notice that it is made of concrete blocks. It would look more like an art installation. Obviously I have too much time to sit around and think this winter.

    • Pam/Digging says:

      Ignoring is an option, but pulling it out isn’t for the reasons described above. Last year the pm disappeared once it got hot. Hopefully that’ll be the case this year too.

      As for the cinderblocks — oh no, I love them au naturel. Concrete is a very Austin look, which pops up all over town in board-form, poured pavers, and building materials. I wouldn’t dream of painting it. That said, I can totally imagine that working for another kind of garden and would love to see it! —Pam

  4. Diana Studer says:

    My fan of Hypoxis leaves
    http://eefalsebay.blogspot.co.za/2016/02/summer-gold-star-Hypoxis-and-fire-on-peers-hill.html

    Leonotis in my garden is also looking paint-splattered. Going to stay with ignore it and hope it’ll recover. I had flowers, and the bush is growing with enthusiasm. (But I may come back to Saurs spray with water solution – but water restrictions here say NOT in the hottest part of the day …)

    I’d leave the concrete blocks just as they are. Urbanite. Grey is one of my favourite colours.

    • Pam/Digging says:

      I just read that wiping the leaves with a damp cloth is one treatment option. I may try that first and stick with it for a while to see if it helps. Hope your leonotis recovers too. As for the concrete, I wouldn’t dream of painting it. And I love gray too. :) —Pam

  5. Tina says:

    Oh, that’s too bad about the Mahonia, because it’s a pretty thing. I’d have to agree though with others–yank that sucker out. Especially since it’s the second year in a row that the mildew has occurred, it’s not likely to make nice for you next winter. My small contribution for FFU–thanks for hosting! http://mygardenersays.com/2016/02/15/twining-vining/

  6. Heather/xericstyle says:

    Have you tried neem oil? If you do, spray at night after the sun goes down. I’d lightly spray the ground underneath too.

    Despite the freckles, I still love that plant there. Good luck, I’m sure it’s gonna recover.

    • Pam/Digging says:

      I haven’t, Heather. I read somewhere that it’s best as a preventative rather than a cure? But I’ll do some more research, and I appreciate the suggestion! I’m such a newbie gardener where plant disease is concerned. Usually I’m all about letting the plants sort themselves out, and they either live or die. But this lingering “paint splatter” on one of my best evergreen shrubs has finally pushed me toward action. —Pam

  7. Jean says:

    Mine is doing the exact same thing. I was just going to leave it but maybe I’ll try what Saurs mentioned. Keep us posted!

    • Pam/Digging says:

      I left it last year, and it did eventually seem to recover. I felt vindicated. But now it’s back and worse than last year, so I think I’m going to try spraying or wiping the leaves with soapy water to see if it helps. —Pam

  8. peter schaar says:

    Too bad about the PM, Pam. I too know less than I should about pathogens and their treatments because I never have any. I’m glad to see your Sedum palmeri is blooming. Mine is starting to bloom as well. Good luck!

    • Pam/Digging says:

      That’s lucky, Peter, and it’s generally been my experience too. And yes, I love the sunny flowers of that sedum! —Pam

      • peter schaar says:

        Pam, I believe it’s more than luck. When you allow your little local ecology to be in balance by gardening organically,as you and I do, problems tend to prompt their own solutions to appear.

        • Pam/Digging says:

          I can’t say that I garden completely organically, Peter, because I do on occasion use a systemic on my susceptible agaves to protect them from the dreaded and deadly snout weevil, and I will resort to Roundup for control of certain weeds like Bermudagrass. I use these as a last resort, not often, carefully and sparingly.

          I agree wholeheartedly with planting plants that are well suited to the local climate and conditions in one’s yard so that they’ll be happy without requiring continual intervention from the gardener. And tolerating a certain level of pest damage and messiness is also important in cultivating a healthy garden ecosystem. It’s all about gardening with Mother Nature, not against her. —Pam

  9. It has been a very unusual winter for landscape plants. I have seen powdery mildew many a time as I live in a place with a lot of humidity, especially in summer. I would advise the use of a good fungicide and repeat. If you do not prefer to use chemicals there are some organic fungicides on the market or you can use a soapy water mixture and apply as needed, but spray on a cloudy day, so not to burn the leaves. I hope this helps.

    Here is my Foliage Follow Up Post…but more snow than folaige this month! http://landscapedesignbylee.blogspot.com/2016/02/garden-bloggers-bloom-day-foliage.html#.VsNqOvkrKUk

  10. Jeanette says:

    I love your cinderblock planting. I was thinking about doing it myself until a friend said that cinderblock has something in it that can damage plants. Do you know anything about that?

  11. Laura says:

    A T of baking soda in a one quart spray bottle of water should do the trick on the PM.

  12. Wendy Moore says:

    A few years ago I found (online) a powdery mildew remedy for Crape Myrtles that involved Skim Milk. It seemed to work, although it smelled a little weird for 24 hours. :-) It doesn’t look any worse than those weird Spider Web Fatsia, in fact I thought it was just speckled like Acuba! I say roll with it.

    Thanks so much for hosting this theme every month, I love the challenge of appreciating the non-blooming stars in the garden! So excited about your talk at TNG on the 27th!

    http://rabidgardener.blogspot.com/2016/02/february-2016-foliage-follow-up.html

  13. Kris P says:

    I hope you can get the mildew under control, Pam, or at least that the problem rectifies itself in time. Here’s my foliage follow-up post: http://krispgarden.blogspot.com/2016/02/foliage-follow-up-february-2016.html

  14. Peter/Outlaw says:

    What Laura said. I sometimes add a drop or two of liquid dish detergent as a surfactant. It’s a beautiful shrub!

    My FFU post is here: http://outlawgarden.blogspot.com/2016/02/foliage-follow-up-february-2016.html

  15. Evan says:

    I have a very minimal approach when it comes to disease control in the garden, too. I’d try Laura’s baking soda approach, with Peter’s suggestion of a bit of liquid detergent added in. Surfactants cause the solution you spray onto the foliage to spread out and stick to the leaves, rather than beading up and rolling right off, making the treatment more effective. Those mahonias still look beautiful and healthy under the powdery mildew. I’d keep them and see if the problem actually becomes a yearly occurrence, not just two freak events in a row. I don’t know how tidy you keep the area around those mahonias, but cleaning up the old leaf litter below the plants can help prevent the PM in the future.

    Here’s my Foliage Follow-up for this month: http://outlawgarden.blogspot.com/2016/01/foliage-follow-up-january-16-late.html

  16. Evan says:

    Um, no, that was Peter’s. Sorry, I copied that to link to in my post. THIS is mine: http://practicalplantgeek.blogspot.com/2016/02/foliage-follow-up-and-wednesday.html

    Geez. This is what I get for staying up too late.

  17. Renee says:

    The succulent wall looks great! It really seems to be holding up well.

  18. Shirley says:

    Sometimes plants just do that and your succulent wall is looking great with our milder winter.

    My growing sedge collection/experiment features in this month’s post:

    http://rockoakdeer.blogspot.com/2016/02/february-2016-foliage-follow-up-sedge.html

  19. Love your new word and all the troubleshooting info I just gleaned!

  20. Sasser says:

    Thanks for a great resource! I have been fighting deer and shade for 25 years and am encouraged to add new shrubs to my 35 boxwoods and 20 society garlic plants which remain standing. Please keep the deer resistant plant suggestions coming, I live on 3 acres and the deer are reproducing faster than my landscaping.

  21. Hannah says:

    I’m sorry to hear of your mildew problems, I know there must be some great suggestions on google. The succulents look great though. I went out today and photographed some evergreens for Foliage Follow-up, I love the green in the winter.

    http://weedingonthewildside.blogspot.com/2016/02/enamored-with-evergreens-february-22.html

  22. Chris says:

    On the natural remedy front, I’ve heard something along the lines of dish soap and Listerine. The Listerine supposedly kills mildew but I wonder since I would think the ingredients might not be too good for the plant. I supposed watered down by a sprayer it can’t be too bad.

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