Blackened needles on Arborvitae Emerald Green

11 years ago

Hello all,

I'm starting a new post after searching & finding this subject pop up a couple of times in the past but never really be resolved. I was concerned yesterday to find a mysterious black patch on our Arborvitae, which has been in the ground just over a month. The patch looks like it has been spray-painted on but the needles feel normal and I couldn't smell anything. Nothing comes off on your hand, it is like a stain which makes me think it is not soot mold. I saw a few suggestions this is due to animal urine which burns/stains the needles and it is close to the base, so I haven't ruled that out. There are a few stray cats around and this is about the height for a cat to spray. The only related posts I've seen re. this kind of black spotting have been re. Emerald Greens as well but maybe it is the way they react?? Having come across some other "interesting" threads here regarding urine, maybe we should do some spot tests of our own...:-)

But seriously - Has anyone else with EG Arborvitae experienced this, what happened, did it spread, did it just fade in time or is it permanent, etc.? I can try posting a photo. Also the tree is about 7 ft., it is in a somewhat damp patch at the corner of our house and gets about 1/2 day of sun, I thought it would be happy with lots of moisture... we also have that awful red clay soil but it's planted with topsoil and mulched. So, any suggestions?

Point 2 - if we do conclude it is urine, how to repell cats?!

Thank you very much!

Comments (15)

  • ken_adrian Adrian MI cold Z5
    11 years ago

    black is NEVER a good thing.. when it comes to foliage ...

    most likely that branch is dead.. or all affected branches .. though i would only trim back the black part .. not green stuff ...

    a picture would be worth a 1000 words ....

    i SUSPECT ... this is a new planting.. at a very large size ... if not.. correct me ...

    if new.. its hard to determine how or where the injury occurred or what is causing the problem ... i mean .. there is a disease process.. but that may have been caused by an injury at transport or planting ...

    if the plant has been there forever ... and this is a brand new problem ... then i would suspect cat or dog.. and anything else that might mark that way ....

    you might try some burlap and a few stakes.. just to keep the critter and urine off the plant ... and perhaps change the animals pattern ...

    i dont put much faith in snake oil repellents ... hence the mechanical cure ...

    on a otherwise healthy plant.. remove the dead parts in spring ... and it will eventually fill in ... as long as the cycle is broken by then ...

    i have had this happen over the yard .. it isnt a plague ... it normally doesnt spread.. and its not that big a deal ...

    i reserve the right to be completely wrong.. if you add pertinent facts... lol ...

    good luck


  • laurafitz
    Original Author
    11 years ago

    Hi Ken,
    Thanks for reply. As I say, it was planted about a month ago and is around 7 feet tall. The branches do not feel brittle etc., parts of them have just turned black. If there was an injury in planting it has taken awhile to manifest itself but maybe it was just thinking about life for a few weeks. As long as it isn't a blight etc. which spreads I'll just wait til spring & trim it off. Hmm maybe burying some mouse traps under the mulch at the base... Will try & upload a photo in case it helps anyone with diagnosis - send in House! :-)

  • wisconsitom
    11 years ago

    It does sound like it's been pee'ed upon. Kens idea of a mechanical barrier is prob. the solution. You know how them critters are.......once one has marked its' territory, it's like a dare for all others who pass by to add to it.

    It sounds like the plant is well sited. And arbs have no dislike of clay.


  • jean001
    11 years ago

    Pee-affected arborvitae I've seen go brown, not black.

    Please post your image.

  • Embothrium
    11 years ago

    I've seen this around here a few times also. It looks like ink. Maybe this guy is talking about the same thing. You do mention your specimen being in a moist situation.

    I am surprised that this is outside your expertise...given the information about you areas of knowledge on the website, it would seem to be precisely up your alley! Do you know of anyone who might have more information on this particular situation (black foliage on arborvitae).
    -Thanks, Todd

    I deal with more trees than shrubs but I did find a one reference of black foliage on Arborvitae.

    "Over-watering can lead to fungus (black sooty coating) appearing on the foliage. In periods of drought your arborvitae should not need to be watered more than once per week"

    I would take a sample to a nursery and ask them if they know what it could be. It could be as simple as an aphid infestation and sooty mold growing on the foliage or a disease that infects the foliage.
    Might also check and see if you have an Agricultural Extension Service off near you they have Horticulturist that can ID these type problems

    [On another subject if you are saying you replaced the soil dug out of the planting hole with topsoil, in future do not do that as it can cause moisture-related problems within the planting hole. Next time refill hole with same soil that came out of it, so new plant has same soil texture throughout entire rooting area]

    Here is a link that might be useful: Plant Diseases: Arbor vitae, agricultural extension service, arbor vitae

  • seeingclearly
    6 years ago

    Arborvitae may have a blackened needle from Pestalotiopsis fungus
    There are no sprays for this You should just pick a dry day and prune black only out of plant.
    Desiccation,winter or other injury, Spray damage may play a rolein this flagging of needles.
    Water plants Deeply and Keep in good vigor , Good luck !

  • mikebotann
    6 years ago

    If it's at the base of the plant and on the side of easiest approach, then it's probably pee. Anywhere else, and it's something else.
    As said above, broken or severely injured branches turn the foliage brown.

  • roadendranch
    5 years ago

    I live in Michigan and I have this same black on Arborvitaes. I see these posts are very old but I am internet researching today trying to get an answer. I have exactly what the original person posted on here. Looks like black spray paint. I will keep searching.

  • roadendranch
    5 years ago

    Thank you for helping me. Kristine

  • stuwhitney
    4 years ago

    I too have exactly what the original person posted. And I too suspect domestic cat urine, although it did not smell like typical cat pee. It is in the right location on the tree and the distribution of the black discolouration fits. What we need is a trained cat so we can test this hypothesis. I will try my own urine but I doubt it will produce such a jet black stain. I will also speak to a vet friend and ask how to get a sample of cat urine. To be continued if I find interesting results.

  • martha_sikes1
    3 years ago

    I'm having those same black leaf issues about a month after planting or earlier. I have clay areas but one area is sandy and still black leaves. I was wondering about overwatering. It said to water 2-3 times a week til established. I would love some help. I love these and don't want to loose them!!

  • ken_adrian Adrian MI cold Z5
    3 years ago

    water when the plant needs water.. insert finger and find out.. let it near dry in between waterings ...

    and then read above about animal urine ...


  • HU-36620415488
    5 months ago

    I/ve been growing different varieties of arborvitaes for 20 yrs now. This is cat pee. The trees are right outside of my kitchen window so I have a good, constant view of them. I cut off the blackened parts every spring. Granular Repel, is the best thing to sprinkle on the ground to keep the cats away. Applied every month.

  • peteypie
    8 days ago

    It’s probably

    honeydew damage