I have been observing the Sweet Brier Rose (R. eglanteria) in our beautiful wildlife garden for a month now since noticing the appearance of these clever and interesting mossy rose galls:
Commonly called Robins Pincushion, the growths are a result of female cynipid rose gall wasps (Diplolepis rosae) laying eggs within emerging foliage buds near the tips of the rose branches earlier this spring.
The resulting gall is formed by a chemical reaction that causes the enlargement and/or rapid proliferation of the plant cells and serves as a protective covering and nutrient supply for the developing larvae inside. Larger galls like the ones on our brier rose contain several chambers and multiple larvae.
The cynipid rose wasp larvae will overwinter inside the galls… if they aren’t invaded first by a number of hungry predators including many of our resident woodpeckers. The mature cynipid wasps will begin to emerge next May with less than 1% of the adults being male. Cynipid rose gall wasps are herbivorous and non-stinging.
Curious what the mature cynipid rose wasps will look like? Check back early next spring and we’ll find out together!
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Wow, those are really freaky. I’ve never seen one. Do the wasps lay eggs in all types of roses?
Ha! You sound like our teens until they knew what the galls were. The rose gall wasps are quite particular about their host plant, and prefer to lay on Rosa canina (dog rose) and its varieties. Hybrid roses are safe!
Wow, I imagine the woodpeckers have a blast with these! I can just picture my little Downy Woodpecker friends clinging to these branches to get a tasty snack.
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We’ve already had several of the galls invaded by our downy woodpeckers. It makes me happy we planted the rose close to our kitchen window where we are seeing glimpses of hungry wildlife at work!
So interesting. Thanks for informative post & pics. What part of the country is this in? Nothing we have in SoCal
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Hi Kathy! I live in Western NY where rose gall wasps frequent many of our wild roses. The galls are incredibly lovely and change color as fall approaches. Simply amazing.
This is fantastic to know Lisa and yippee for woodpecker food. Isn’t nature grand!
Always! Now here’s to hoping I can snap a lovely shot of one as they discover the galls!
Oooh, the photos make the galls look actually quite pretty! Like a flower or a sea urchin having a bad hair day! I haven’t seen these on our wild roses (we have swamp and virginia rose growing here) in Mass. but I will look for them. Anything that feeds our overwintering downy woodpeckers is welcome to make its home here!
They are urchin-like with those filaments covering them!
I have seen the galls on wild roses in our local state park as well, they’re nicely visible in autumn as they turn a burnished color. We have 11 total on our shrub right now, I wonder how many will survive until next spring?
GET OUTTA HERE! This is the coolest thing I learned all week. Beautiful wildlife Indeed! I can see the business now, selling these cynipid rose wasp larvae will overwinter inside the galls.
I know! Very cool! Another great thing about the rose gall wasp? Damage to the rose plant is minimal to none, and if there are large numbers of galls they can just be pruned off. No pesticides are effective against them…nor are they needed! Amazing!
I have the sweet briar rose in my gardens, and saw this gall this Spring!
I knew that it was a “gall” somehow, but not the source of it.
I am in Berlin , MA. We have many types of woodpeckers here!
Don’t you just love the rose?? Fragrant, lovely and beneficial to wildlife! Not only the wasps but the birds that love to eat the rose hips. Your woodpeckers and others will be very happy!
Be sure to let us know who you see feeding from the galls. 
Lisa, this is amazing – nature never fails to make my jaw drop. Thanks for sharing!
Now I know what these are. I first noticed them a couple of years ago in a Nootka rose (those grow wild around here, in Oregon in the Columbia River Gorge), and thought they might be a fungus of some kind. We get occasional woodpeckers, but mostly Flickers (a part of the woodpecker family)–wonder if they eat these too?
We have Northern Flickers as well, such a beautiful woodpecker and wonderful for ridding our sandy soil of ants! I haven’t noticed the Flickers near the galls yet, I’ll keep you posted…and please do the same!