Knopper Galls or the mystery behind the mutated acorn



Behind our house there is a lovely big oak tree and this year I’ve noticed that the acorns all seemed a bit unusual….they didn’t look very “acorny” in the slightest….I’ve found out that the “mutated” acorns are in fact Knopper galls which are caused by a tiny Gall wasp.


knopper galls


The odd acorn seems to have avoided infection but the majority are all lumpy and misshapen…..


mutated acorns


The lumpy galls remind me of some of the mischievously faced pixie, sprites and green men drawn by Brian Froud in one of his Faery books.




I’m pretty sure I’ve not seen these galls on this tree before, so maybe the infection is something that has happened recently.

As far as I can understand this gall has only been recorded in the UK since the fifties.  The wasp which makes the gall needs two species of Oak tree to complete it’s life cycle, first the native English Oak ( pendunculate oak, or sometimes in the sessile oak) and then the Turkey Oak, which isn’t a native tree in the UK but was introduced in some of the large country estates in the eighteenth century.  The wasp itself is believed to have been blown over from the rest of Europe during high winds.




Every so often I saw a proper looking acorn and gave a little cheer….for me these are the most easily identifiable nuts of a tree, and it makes me feel sad to think this poor old tree has been infected.




Just around the corner there are some Horse Chestnut trees….along with the Oak tree, this is one of my favourite trees.  Because of their size, it’s always really easy to observe the changing season through their leaves, blossoms or fruits…..

In the Winter the trees are so barren and bleak looking, heavy and dark silhouettes against moody skies, when it snows they look like giants under a blanket…then slowly huge fat sticky brown buds begin to appear, when they open they are the most intense, bright green and they remind me of tiny cos lettuces, growing along the branches of the the trees……all of a sudden the blossoms begin to appear, they are a mass of white and fill the air with their sweet perfume (which is a real problem if you are unlucky enough to suffer from hay-fever, their pollen blows around at the merest whisper of a breeze)…..gradually the blossoms form tiny fat spiky fruits which drop to leave just a handful behind on the blossom stem….when we start seeing these tiny spiky fruits on the ground it’s with a sigh of the heart, a sign that Summer won’t last…….then their bright green leaves begin to turn brown, the colours as rich and as deep as the brown of the conker inside those lumpy spiky shells….. a word of warning…don’t walk under a Horse Chestnut tree when it’s windy..I’ve been clouted on the head by a falling conker several times before now and it packs a right old wallop, once the fruits fall they split open to reveal beautiful shining conkers…I still like to rummage around underneath the trees to pick them up and pop into my pocket.  I always say I’m gathering them for Bernard to play with…but really it’s for the simple pleasure of touching them, the smooth cool feel of the nut, the memories I associate with them, playing conkers in the playground where I’d squeeze my eyes shut and hold the conker on a ratty bit of string with my arm outstretched…and of course that advert  which I’m sure many ladies (and gentlemen) of a certain age will remember with great fondness ….. (who wouldn’t still like to find one tucked away in their packed lunches…….they remain one of my favourite guilty pleasures and in the Autumn when I’m walking home, I’m always very happy to retrieve one from the bottom of a handbag)




And under the Horse Chestnut, there is a great swathe of yarrow, with blossoms all whipped and billowy in candy floss looking swirls, ready to unfurl and greet the mid Summer sunshine.

5 thoughts on “Knopper Galls or the mystery behind the mutated acorn

    1. I definitely saw some of these infected acorns about Autumn 16 but I’m not sure about the Autumn before that as I managed to lose my nature notebook where I wrote down things I was seeing, when I was out foraging …

    2. I found mutations on many trees in Glasgow.
      Would anyone of you think this might be also caused by the constant spraying of toxins and heavy metals?
      Watch the sky for Geo-Engeneering trails the planes are leaving behind. It is not vapour if the trail stays and spreads out to block out the sun.

      1. Certainly these galls are caused by the wasp infection but wouldn’t be at all surprised to hear of problems arising from heavy metals and chemicals used in industry/farming etc

      2. Yes, it might cause an imbalance in favour of the impact of the Gall wasps.
        Other plants are also mutating and THAT is shocking for me to observe,
        a sign of human blinded ignorance and lack of respond-ability.

        I do hope people to wake up and join the many ways to bring about change!

        Thank you 🙂

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