Sunday, March 7, 2010

The Sad Black Oak: Q&A

Above and below is a massive black oak (Quercus velutina) that towers over crabapple and corylopsis along a woodland slope in Central Park.
Thanks for your help Alex.
I really appreciate you giving it some thought. Basically my attitude has been to let nature take its course and maybe the tree will be fine, maybe not.

A brief history:
It was fine looking two years ago. Then last spring it barely flushed out and just had these puffs or pom poms of leaves at the tips of some of the branches. Other parts of the tree were bare all year. Fall came and the leaves that were on the tree died back normally.

The tree is too tall to see what the buds are looking like yet, if there even are any in the first place. Plus I can't reach up and grab a branch to see if it's dead or not because I am just five and half feet tall and the tree is more like sixty feet tall.

Hi Cassady,

It’s been fun researching Quercus velutina and trying to figure out what might be going on. Not to mention I might be able to repost this to my blog and see if other people have feedback. So I know this is going to be pretty wordy but I want to be sure and cover all the basics. As I said, there is a beautiful black oak I know of in Central Park and it too is close to 60’ if not taller. Someone asked me to identify it for them one day and I was stumped because obviously the foliage was well out of reach and all I had to go on was the bark. Ultimately it would be a combination of the leaf and the heavy gray pubescence on the buds of fallen twigs that would allow me to confirm my hunch for certain. But I love the tree because it’s a giant statement in the landscape.

But I love the tree because it’s a giant statement in the landscape.

So they are a native tree of course and their range is huge. It appears that they are happiest in a humus-rich woodland soil but thanks to the development of a serious tap root they also do fine situated in poorer conditions, whether dry and sandy or heavy clay. Since we have always grown up with oaks I share your same sentiment that we don’t typically think of them as being problematic trees or requiring much fuss. Most references don’t even mention common pests or diseases and I couldn’t figure that out so I dug a little deeper. I realized that might be the case because once you get into it different species in the red oak group are susceptible to a slew of fungal diseases and pests. Authors probably figure it’s easier not to go there. And in part they are right because most of the fungal issues that affect oaks are not going to become serious enough to kill a whole tree. The list typically reads as follows: Anthracnose, canker, leaf blister, oak wilt, smooth patch, wood rots and decays.

Luckily I think most things you can rule out right away. Canker you usually find more among woodland trees and those big bulgy symptoms would be obvious. The same goes for major rot issues, you would see some signs of fungal conks or mushrooms near the tree. Not to mention I assume it is probably pretty dry where the tree is, right? Given the fact that it’s the island and in a front yard and not a more woody setting. If it was leaf blister or a gall forming pest that too I would think you would have seen signs of in the leaf litter last the fall when the tree defoliated. That leaves me thinking about Anthracnose and oak wilt.

Oak wilt is a disease that can kill a tree quite rapidly once infected. It is a big scare among nurserymen because it can spread quickly between root systems and take out whole monoculture plantings in no time. But I don’t get the feeling that this is a disease homeowners deal with very much, and most people that write about it are more in the Midwest so I don’t know how prevalent it is here in the northeast. Just the same the University of Illinois Extension has some good info on Quercus velutina and associated issues and you should check them out: ( To rule out oak wilt try and find some downed twigs after the next storm and whittle away the bark with a knife. Oak wilt causes a brown vascular streaking in the active layer of the cambium and is supposedly pretty easy to spot. The other reason I am not sure about oak wilt is that they say the tree dies quickly from the top down and it sounds like you are dealing with the older foliage going first leaving just the new growth.

Lastly there is Anthracnose. Anthracnose usually affects foliage on big shade trees and again is rarely bad enough to kill a tree. Usually you see irregular patches of foliage affected and though ugly the tree still looks decent overall. That being said, if enough of the foliage becomes affected and the tree can’t properly photosynthesize because it is big and old and on a slower schedule compared to the fast spreading fungus then it can become quite the issue. I have seen anthracnose attack a ton of different trees, and usually they can re-foliate and make it through. But anthracnose thrives in uncommonly wet and rainy conditions and with that I can’t help but remember how brutally wet it was the beginning of last summer. And to make matters worse late summer last year went to the other extreme and things were very dry and heat stressed as a result. So I wonder if the anthracnose was there but not such an issue for a few years and then irregular wet and dry helped to feed the fungus and put the tree into a bit of a tail spin.

Either way it sounds like you are not left with much active living wood compared to how big the tree is. Personally I would wait and see what foliage is produced this spring but maybe not hold your breath. If the foliage is less than half of the entire tree then I would guess it looks pretty terrible and would not be able to rebound before dying completely, though that could take a few years still. And then of course you have to think about the non-cultural conditions, where it is in the front yard and the kids and the house and all that. Even though we know oaks to be a tough hardwood tree if all you are getting is the new growth and the rest looks like a skeleton I’d be tempted to have it taken down before some freak storm does it for you.

The one that is near me has a pretty serious lean after some of these major windstorms and winter damage and years of abuse and we often wonder how long it will hold on. But in my situation the tree is in a very soil-rich and wet spot with lots of protected plantings around it so I think the vascular system is still chugging along and giving the tree the water and nutrients it needs to hold on.

So sorry I am not giving a definite diagnosis but I hope I was able to give some thoughts and points that help you in the decision process. If I can help any further feel free to let me know and we’ll take another stab at it.

Best of luck and keep me posted!

Alex Feleppa

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