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Tuesday, July 31, 2012

Impatiens destroyed by Downy Mildew

I’ll admit it, impatiens were never at the top of my list of favorite garden plants. Everybody and anybody plants impatiens. Sure, they are cute and easy to grow, but I've always been drawn to the slow growing/bloom-for-only-a-few-weeks type of perennial.  Bottom line, they didn’t excite me. For the past eight years, I’ve lived in rental houses where I was forced to grow plants only in containers. I vowed that when I finally bought a house, I would not plant impatiens. Being a horticulturist, I knew there were other, more unique and intriguing plants out there that would thrive in the shady areas.

Impatiens walleriana

Nevertheless, after buying our first house this winter, I found myself drawn toward impatiens for my yard. I have come to realize there really is a place for this showy annual among the perennials and shrubs in one’s garden. A bland spot under the hedge in the front of my house needed a punch of color and within week, bam! the “Salsa Mix” Impatiens brightened it up. And then, after we removed a the  Juniper shrub from under the weeping cherry tree, I needed some quick color in there. A bunch of white impatiens did the job beautifully. 



Beautifully, that is, until one week ago...


At first, I thought something was eating the impatiens. In a large spot near the road, the plants were missing their flowers. But since the plants further back on the property still looked good, I thought it was a rabbit (further convinced after I saw a rabbit one morning just sitting innocently on my front lawn – a sight not common in my neighborhood!).  I bought some organic rabbit and deer spray to deter the creature and put down some fertilizer to encourage more blooms. But nothing worked. And then I received an email from a local nursery. It started with “Do you still have impatiens? Well, enjoy them while they last because Downy Mildew is destroying them across Long Island.” Not knowing what that was, I did some research and it turns out that Downy Mildew, Plasmopara obducens, is causing gardening (and growing!) havoc throughout various parts of the US this year. Symptoms include yellowing or stippling of the leaves, leaf margins curling downward, stunted growth, flower drop and white downy-like growth on the underside of leaves. The fungal disease can cause complete defoliation or plant collapse especially in landscape plantings under cool, moist conditions.
I realized my plants were not being eaten, they were being destroyed by this disease.

Downy-like fungal growth on the underside of the leaves

Downy mildew is a water mold. It likes and requires moisture to sporulate and cause new infections. Locations where the leaves stay wet for extended periods of time (either from dense plantings, overhead irrigation or excessive rainfall & humidity) are more susceptible. 
Read more about Downy Mildew here.


Apparently, regional outbreaks were common in 2011 and are spreading into 2012 due to spores over wintering in landscape beds. There is no control of Downy Mildew and it’s recommended that infected plants be removed immediately, placed into plastic bags and discarded. If fungal-laid leaves get into the soil, the spores may continue to live there for 3 years. So if you think you can just plant new impatiens next year, think again. A better bet would be to plant new guinea impatiens, coleus or begonias.

According to mainstreetnursery.com, it’s believed that because seed companies have been hybridizing impatiens to gain desired characteristics, the impatiens’ previous resistance to the disease has been bred away over time.

Yesterday, I sadly removed all my impatiens. Even the ones that looked good from above, had the tell-tale whiteness on the underside of the leaves. In their place, I planted some variegated coleus and white begonias with attractive brown foliage. I know it's late in the season (and frankly, it was slim pickings for me at the nursery!) but I do hope these will grow quickly enough and provide some color until frost. 

Turns out, I will miss my easy going impatiens after all, and hope to have them in my garden again one day. 


Sad state of affairs for these impatiens

What about you? Have you seen this problem in your area?


More about the impact of Downy Mildew on Impatiens walleriana:
http://www.greenhousegrower.com/article/26190/opinion-impatiens-put-to-the-test

29 comments:

  1. Thank you so much for this article. My mom insisted my flowers were being eaten by rabbits. I read this and rushed out to check my remaining flowers. Sure enough... downy mildew. Money down the drain but at least now I know!

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  2. Its so frustrating I know. Glad I could help though!

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  3. Thank you for your article. I just could not understand why I couldn't grow impatiens this year. They always helped with color and were easy in my boxes.

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  4. Hi Kate,

    Mildew has been a real issue this year with the early spring, constant heat and humidity we've had this season. This was a very important and informative post that will probably be beneficial to many.

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  5. Hi Lee - I agree, this summer has been a sticky one! Glad you enjoyed the post.

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  6. Going out to check my leaves now but my plants look just like those in your pictures. Very sad and the fact that it will last a few years is even worse. I really dislike mums but perhaps I will need to plant a few this year just to have some color till the frost comes. Thank you for your help! Ps-I was thinking it had something to do with all the rain we are getting on Long Island this summer!

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  7. Mums are a good idea - asters might also fit the bill for some color till the frost. We still have a lot of warm days ahead to enjoy something to fill the impatiens void!

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  8. Hi Kate
    What a shame!! That first shot of the white impatiens under the tree was so lovely! But then downy mildew destroyed your lovely white accent plant.
    It's been a weird summer. Excessive heat and humidity up here in Ontario as well and hardly any rain. The few impatiens I have are still hanging on, thank goodness. It's too bad other small white accent annuals like alyssum and ageratum need sun otherwise you could have planted them.
    But at least you know why this happened…...

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  9. Mildew is every gardener's worst nightmare, especially those who have rose bushes. The most known and most common mildew that effects rose bushes is one known as sphaerotheca pannosa. This type of mildew is powdery. The mildew is usually a white or grey powder that is usually found on rose bush leaves, shoots, buds, and the petals.

    Mould Removal Toronto

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  10. yup, same here in rahway nj! 8 flats of impatiens gone! and clover taking over the garden! at least i know what the problem is, i thought it was something i did wrong, as ive planted them for the last 10 yrs or so and always had a beautiful showing by now. so sad, but maybe time to find new plantings for next season!

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  11. The same happened here in MD. I had lovely mounds of red and coral impatiens about three weeks ago. I went away for the weekend and came back to stems. Like you, I was sure it was rabbits, so I spread blood meal, which usually helps. But then I noticed that even the plants in my planter were affected, and some were just turning to slime. I looked under the leaves and discovered the same mildew under the leaves. At least the begonias planted interspersed with the impatiens are okay, but it was sad to pull all my impatiens out so early. Thanks for the informative article - I likely would have just planted again next year. I guess I'll find an alternative for the next few years to be safe.

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  12. I have the same problem in the greater Toronto area in Southern Ontario. One by one my impatiens are dying from Downy Mildew. Not sure what I'm going to plant next year as deer and other animals munch on all my other annuals and yet they seem to avoid impatiens.

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  13. Same problem with impatiens in central Toronto.

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  14. So interesting to hear from so many of you around the continent having the same problem! Such a shame - lets hope it is better next year.

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  15. We planted impatients this year instead of begonias and salvia and those pretty little purple flowers (we usually try to keep a red, white and blue theme for the summer) white begonias, red salvia and purple (blue) little flowers cannot remember their name right now. However, this year we decided to go back to impatients as we had an in ground sprinkler system installed and knew impatients like water and flourish well when watered. Prior years before installing the sprinkler system our impatients used to droop by the end of each day and we had to manually water them after the heat of the afternoon. We planted impatients around our trees and flower beds and also in several pots to enhance areas where there is no soil. They looked great and then I noticed they were not flurishing in volume and thought the extreme heat and humidity may be effecting them. Well, a few days later when leaving our house all the impatients were completely gone, everywhere. The flower beds were stark, the circumference of the trees were bare and the pots were empty. We too thought a rabbit or squirrel were eating them but how could they disappear so quickly. We waited a few weeks stupidly thinking they would re-appear and then we received an e-mail from our local green house telling us about the downy mildew. Since that time one of our nephews who just loves flowers and does a lot of planting sent us this article and it was so informative. Just this week we tilled the soil and purchased some small mum plantings and filled in some of the more obvious spots and hope they survive for a while. We usually plant some of the cabbages and sprinkle in some small mums at the end of the summer when the impatients get leggy but they never grew at all and just disappeared totally. To make matters worse, our lawns are also suffering this year and nothing looks good. We hope the return to some cooler temperatures and some gentle thatching and re-seeding will bring our lawn back. We will not give up and just enjoy seeing pretty flowers for as long as we can. As mentioned above we had previously planted those cabbages and sprinkled in some small mums and/or some winter pansies and the pansies actually lived for a long time after the frost and were even popping up through light snow which was amazing. Neighbors stopped to comment when they saw them and thought we had placed artifical pansies in the ground.
    Thanks so much for this article and also the additional info to not plant impatients in the same areas going forward for 3 years. We are happy to get this information and still love impatients even though this was not a good year for them.

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  16. I live in Roselle, NJ. and always plant impatiens in containers and in beds for the color. The flower beds began to die off in mid June, and I also assumed rabbits and a groundhog were dining on my flowers as they have done so, in the past. I actually created a little stockade with barbecue skewers and replaced the impatiens in those beds, only to see them die off also. I have one container left that has managed to survive. I'm glad to know what is causing the problem. I noticed very few impatiens in this area of NJ. and almost none in the shore area this summer. I guess it will be coleus in my shaded spots for a few years!

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  17. Mine all had it too! (Massapequa, Long Island) :( Thanks for this article and the information that the spores could last 3 years. These super easy shading loving annuals will be missed!!!

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  18. Had very similar experience. Now the same is happening to lilac bushes. Could the mold have affected these plants as well? Are other having similar trouble? Wondering if I should rid the garden of these bushes too so as not to spread the disease. What do you think?

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    1. Most likely the lilacs are not infected with downy mildew (though can't be sure without seeing a photo), but rather it's plagued by the common lilac problem called Powdery Mildew. That happens when there is not enough air circulation or sunlight for the plant. It doesn't kill the plant, but just makes it look less attractive. Clean up the leaves now as they fall to try to keep the problem at bay for next year. The best way to control powdery mildew is to prevent its occurrence. The disease develops most rapidly in dense, shady and damp conditions.
      If it continues to be a problem for you, consider replacing them with disease resistant cultivars and varieties.

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  19. I couldn't figure why my impatiens were all dying last summer. I live in Pittsburgh, PA and impatiens have always been a wonderfully hardy flower that stays in bloom almost all year. Do you know if this Downy Mildew affects other plants? What other plants can I plant now?

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    1. Unfortunately you can't even plant the impatiens again this year because the fungus is in the soil and will take a few years to get rid of it. So this year, try planting begonias, new guinea impatiens, coleus, sweet potato vine, torenia or caladium. Good luck!

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  20. Kate, I'm so happy I came across your blog. I couldn't understand why my inpatients just died on me last summer. Now that winter is gone and Spring is here, can I plant inpatients this summer or is the Downy Inpatient fungus still a threat? I don't want to plant them and have them die again. Thank you, Sandy

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    1. The fungus lives in the soil, so you can't plant impatiens this year either. Try something new - begonias, new guinea impatiens, caladiums, sweet potato vines. There are lots of annuals that enjoy the same conditions impatiens do. Most nurseries are not even selling impatiens this year because of the Downy Mildew.

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  21. I have heard that you should replace the soil where impatients were planted. I shtis true?

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    1. The fungus will live in the soil for about 3 years. So you could replace it, but you must be thorough. Or, you can just plant something else for the next few years.

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  22. Wow my plants looked just like your pics I planted 25 flats as usual and they looked great for our towns annual flower walk in July my yard looked terrific till the middle of august then they went from great to looking like, well you know !!!!!! I am just heart sick and am having a terrible time figuring out what to plant because I loved the constant flowers all summer!

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    1. I know, it's really a shame. But hey, its a good excuse to go try some new plants! I've got some beautiful begonias blooming where I would have normally had impatiens. Good luck!

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    2. I always planted and got so many compliments on my colorful impatience and how big they got since we always took care of them and fed them and watered faithfully, but today I am pulling them all out and it is just August they are gone and stragly stems are all we have left I am so upset as I bought these all at a reputable garden shop and paid a pretty penny to mathc the pretty colors. Why would they sell them if they were not a good plant? And now I can't plant ehm for 3 years I am very disappointed, but will move on with something new.
      Thanks so much for all the info from everyone.

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