Interesting looking specimen
I have something almost scientific and accurate to share with you. I’m 92.5% certain that the above looking ball is an oak or apple gall. And if that’s the case, it was formed by a gall wasp.
But that’s skipping ahead of the story. It all started the other night when Barry recruited our son to help trim some oak branches which were growing perilously toward the electrical wires. (He was planning to recruit me, a fact I was lamenting for several weeks.) It involved propping a ladder in the Studebaker truck and hand-cutting some oak branches. He insisted it wasn’t dangerous. Since he’s a rather cautious fellow, he was probably right. Nonetheless, I really didn’t want to be part of this particular adventure.
The culprit. The oak tree which grew too close to the electric wires.
Hmmm, the photo makes it look more dangerous than it is. Perhaps it shouldn’t have been included in this little gall-filled discussion.
Anyway, in less than ten minutes the chore was done. The offending branches fell to the ground. The crew leaned close to look at the acorns and (I’m sure) gasped. What were those strange green balls? What were they doing on our oak tree?
Another view of the strange green ball growing near acorns
We all pondered, but couldn’t come up with a plausible explanation. Someone opened up the ball to examine the innards. Even more interesting, wouldn’t you say?
Spidery inside of the ball
Today I thought to google the key words “green balls on oak trees”. One of the interesting features of WordPress is the capacity to tell you what people searched to find your blog. You learn that people type in all sorts of strange words. Today people found my blog by typing in “I have caterpillars in my birch tree” and “sand movement on Lake Superior” and “wrought iron moose bear driveway gate”. It always somewhat amuses me to think that anyone is searching for anything scientific in this blog. The last search sounds more like the stories you’ll find here.
Anyway! This Internet world is amazing. At your fingertips you can discover what the heck those green balls are in your oak trees. Here is one credible explanation offered by someone in a group forum:
Q: My Oak tree has large green balls hanging from the branches. I have seen these before, but never to this extent. How can I get rid of these?
A: The round growths you see on your oak are apple galls, which is another name for cynipid wasp nurseries. These growths are part of a fascinating arrangement between insects and oaks. The tiny wasps lay eggs on oaks, stimulating the plant tissue to grow at a rapid rate. The eggs become encapsulated, and the ensuing gall providing food and shelter for the emerging larvae. Different kinds of cynipids wasps will lay their eggs on bark, leaves, branches root, leaves and acorns, each one causing a different kind of gall to form in a very specific location and at a specific time. They range from the tiny jumping gall, to the large apple gall, and from white to red to brown to green. These galls for the most part do not harm the plant, although one leaf gall will cause leaves to turn brown and fall of. The trees are not harmed in the process, and as the wasps are so tiny with such complex lifecycles, preventing their appearance is not practical or possible. You can knock them off of the tree if they really bother you, but know that they will be back next year. If you would like to see the wasps, collect the galls in the late summer/fall and place them in sealed bags. The wasps will emerge in the early spring.
If you don’t believe all the facts in the preceding paragraph please click on this Wikipedia link to learn more about the gall wasp and its oak balls. Fascinating reading. (Just kidding! I just skimmed to see whether it looked plausible.)
My husband carrying off the oak branch (and its balls)
Finally, today’s outdoor activities: coffee/tea on the deck before 8 a.m., a little gardening in the afternoon and wood splitting in the evening. Day 189 checked off!
Opening the door, walking outside 
11 comments
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June 27, 2009 at 8:15 pm
xenophilicx
That’s crazy! It sounds so interesting, too. I wish I could learn about this kind of stuff in my biology class. I’m totally not a plant person, but this made me think twice!
I guess plants could be pretty interesting.
June 28, 2009 at 12:42 am
flandrumhill
Nature is SO cool isn’t it? There are some pretty large galls on the trunks of some of the trees in the here. I’ve always wondered what caused them.
I wonder how the insects emerge. Do they eat their way out?
June 28, 2009 at 7:44 am
Emma
What??? This is quite interesting! Could you see wasp eggs in there? Or would they be too small to notice?
P.S. I love the title of this post. 🙂
June 28, 2009 at 2:24 pm
Deborah
Of course, it is a gall. I’ve seen many in the last couple of years as my 8 yr old son loves to collect Oak Galls. He likes to peel them open and find the little insect inside. I didn’t realize it was a Wasp larvae but then they lay eggs on Tomato Hornworms, so why not cause galls on Oaks. Alot of trees have galls. Wild Azaleas get them, they look like some kind of small green squash and are more solid than those on the Oaks. Cedar trees have rust apples. Nature certainly is prolific ! ! !
We have enough wasps of all kinds though. I don’t think I’ll tell my son about keeping them in a bag until Spring. Gasp. We’ve actually had these “harmless” looking brown balls on the kitchen window sill . . . so, that’s how the Wasps got in the house this Spring ! ! ! Or else someone let them in the screen door from the porch they love to drink Hummingbird Water from.
Deb
June 28, 2009 at 6:13 pm
centria
xenophilicx, your comment made me smile. You want to know a secret? Most of my life I wasn’t a plant person either. In fact all this stuff kind of bored me. But it’s really exciting! At least it’s interesting, once you start to look at this kind of stuff with “new” eyes…
Amy, hmmm, I don’t know if they eat their way out. Didn’t the article tell that part? I’ve seen large galls on trees too, but didn’t know what they were. Aren’t some gall-looking things on trees just mis-shapen growths? Or are they all galls? Hmmm, the plot thickens.
Emma, I didn’t look close enough at the one that was open to tell. Mostly because when we looked, we didn’t know WHAT we were looking for, so we didn’t peer too closely. If I get some spare time, maybe that should be an assignment? tee hee, glad you liked the title!
Deborah, I should have interviewed your son for the blog! He probably could have shared lots of stuff with us. Smiling at your story of the wasps inside your house. We have quite a few who wander in, as well, mostly through the screen door. Our house is made of cedar with knotholes, so they like to buzz in and out of the holes. Sometimes in the summer when we sit on the deck the wasps are buzzing all around us. I don’t mind if they land on me, because they usually head off immediately. But last summer one came in on a bunch of green onions from the garden and stung me. NOT FUN! It was terribly painful, and then red lines started going up from the sting toward my underarm and the doctor prescribed antibiotics. But it was my fault cuz I grabbed the green onion and scared him.
November 10, 2009 at 5:05 pm
Killarney National Park Visit « Guerrilla Forestry
[…] The forest floor was a veritable carpet of fallen leaves and I got some nice photos of moss, holly berries and oak leaves. My companion also identified a rather strange growth I found on the underside of an oak leaf as an “Oak Gall”". The gall was formed by wasp larvae that cause a mutation in the tree that manifests itself as a gall. I tried to find some more info on it and found this interesting blog. […]
December 17, 2009 at 7:31 pm
Greatest hits for the outdoor commitment « Opening the door, walking outside
[…] is The gall of that oak tree! That was the exciting day when we discovered that oak trees often grow green balls known as […]
September 4, 2010 at 6:53 pm
Nancy Green
Well, the inside of your apple gall looks like the inside of mine. I have an entire tree that sprouts these things in the spring. They look like part of the tree and it’s been driving me crazy. I found your blog by googling oak tree balls and then just looking at the images. I wouldn’t have believed it with out the picture. Thanks for the sanity!!! I’ve never found a larva or an insect inside, but I wasn’t looking for one either.
Just in case you’re curious, I live near Kansas City MO. Guess this little bug lives all over the place.
June 26, 2012 at 8:29 am
JT
Thanks for solving a great mystery for our family. We were hiking on a trail and saw these all over the place on scrub oak. There were signs to say watch out for the wasps but I was looking for regular backyard type wasps and didn’t see any of those. The clues were right in front of us but I had never heard of galls before or knew of this type of wasp. Very interesting. Thanks!
June 26, 2012 at 11:16 am
Kathy
Very happy to have solved the mystery for you!
June 27, 2015 at 9:28 am
Elisa
OOO even after all of this time, one i did not read! Still working on my health and safety. I miss your writing and i was thinking about our strange companionship. I hope you are well. 🙂