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Cause of rhodie leaf damage/loss?

Discussion in 'Landscape Maintenance' started by lakesregionscapes, May 19, 2012.

  1. lakesregionscapes

    lakesregionscapes LawnSite Member
    Messages: 147

    Hope this is the right sub-forum. I was hoping a different set of eyes might help us determine what went wrong... 5 large healthy rhodies, planted last summer, came through the winter fine; early April they looked good - no damage, or winter burn. Got a call from the customer today - shrubs look terrible - need to be replaced.
    No one has been there this spring, except maybe a carpenter. We're in Central NH, and we had a really dry spring (no rain in March and April), but it has been raining a lot since. Went over to look, and take pics. Two shrubs are 2/3 damaged, 3 are just about wiped out.
    I added the landscape photos from last fall to show their location and environment. Mostly shady, hemlocks and moss, bottom end of a steep hill with odd, talcum powder fine, orangy-beige soil, we amended before planting with better loam and hydrogel. Rhodies generally do really well around here and are very common.
    Hubby is feeling like it looks like chem burn, but from where? New buds seem green and developing. Fungal? Soil issue? Drought stress?(hard sell after 3-4 weeks of rain, but no-one has been there in 6 weeks)
    To me the really weird part is that there were OK 6 weeks ago...




  2. phasthound

    phasthound LawnSite Fanatic
    Messages: 5,047

  3. bamaturf

    bamaturf LawnSite Member
    from alabama
    Messages: 136

    rhodies dont like wet feet. either elevate or move them further up the hill in the bed, or trim trees to let more light in. my 2 cents. had a similar situation
    last year & rhodies looked bad, then a storm got a near by tree. this year
    rhodies look a lot better w/ more blooms
  4. Dr.NewEarth

    Dr.NewEarth LawnSite Bronze Member
    Messages: 1,476

    How was your winter?

    I am guessing your problem is from ground water and the native soil.
    It is possibly "Armillaria" root rot.

    I wonder if you are also seeing "allelopathy" from the Hemlock roots?

    Get a lab test as Barry has suggested.

    It's some-times difficult for us to see all of the factors that could contribute to plant decline, from a picture.

    I always have many more
    questions, inspections and tests that I can do in person.
  5. lakesregionscapes

    lakesregionscapes LawnSite Member
    Messages: 147

    Figured I'd follow up with an expert's conclusion so if someone else is searching this issue they get the final input, for our specific case.
    Since thanks to the state budget cutbacks our cooperative extension is under-funded, under-staffed and over-worked and in the peak of their busy season, I decided to first pester our local Barlett Tree expert, who consults with landscape contractors quite willingly, and cares for trees on several of our other clients' properties. He got out there to take a look and got back to me within a couple of days...
    He's quite sure it is winter burn, despite the very late manifestation. We had a dry fall, minimal snowfall (no snowmelt in spring) and a two month drought (March-April). There has been record rhodie damage all around the region, often on shrubs that never suffer usually.
    He explained that although the stress damage occurs over the winter, the signs don't appear until the growing season starts, and on this location that is nearly a month behind the rest of the area. Painted ferns onsite were up barely an inch, while they're fully leafed out everywhere else in town. The shrubs in the shade were less damaged, roots are all sound (shrubs have been pulled) and what new growth there is looks healthy... The rhodies were pulled yesterday. Since we first saw them 2 weeks ago, the rest of the leaves had dropped, and they actually look more like we are used to seeing in spring, after a tough winter (horrible). We seem to have just caught them earlier than usual in the progression of symptoms, while the burns were still working their way up the leaf length.
    The salvaged plants are going in our yard, and the replacements will be getting wrapped for the winter at least until they are well established. We're planning to replace at cost, to split the pain. Bartlett felt the location was a bit shady in the top (thin the canopy a bit), but otherwise fine (we selected specifically shade tolerant varieties). The location is tough and there aren't any better evergreen candidates, so rhodies remain the choice... The hill is too steep for wet feet to be a concern.

    Thank you to all of you who weighed in, I always appreciate the range of knowledge in this forum.
  6. Dr.NewEarth

    Dr.NewEarth LawnSite Bronze Member
    Messages: 1,476

    I still believe you should get a test. Have you pulled out one of the plants to check the rootball. If you can do that, get another picture please.
  7. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    Winter burn is another way of saying, drought... protecting the plants from dessicating winds is fine, but the real issue with struggling landscapes is, water...

    I learned from fruit tree farming that the water available in September determines the size and vigor of the fruit in the following season... I keep landscapes soaked as much as possible until the ground freezes...
  8. rlitman

    rlitman LawnSite Bronze Member
    Messages: 1,732

    Drought is not the total answer. Rhododendrons can't just soak up water from the ground when the ground is frozen. You can't water them in the winter, so watering isn't going to help this. By the spring, the damage is long done, and watering then is just too late.
    Watering well in the fall does indeed help, but only to a degree.

    Protecting from desiccating winds helps. Another option is to spray with a product that helps seal the stomata, such as Wilt Pruf, or an oil product.
  9. Smallaxe

    Smallaxe LawnSite Fanatic
    Messages: 10,082

    Winter kill occurs with plants that go into the winter, with less than robust water reserves... if they don't get snow cover they are reliant upon roots below the frost line to access moisture, so there needs to be moisture down there before winter comes... correct preparation is done automatically by the plant itself as long as it has enough water to prepare...
    Winter kill is drought and drought alone... if there is another cause, then we need to know that...
    Just because some plants, like Japanese Yews, can never prepare for a Zone 3 winter, especially if planted out in the open; doesn't mean there was something other than lack of water causing the winter kill...
  10. Mark Oomkes

    Mark Oomkes LawnSite Fanatic
    Messages: 14,910

    I would hazard a guess that you also have some Phytophthora going on as well.

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