Galls: Cecidophyes nudus

07 Tuesday Jul 2026

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British galls, Cecidophyes nudus, gall-causing mites, galls caused by mites, galls on Geum urbanum, Galls on Wood avens

As a wise person once said (I’m looking at you, Theresa Green), ‘there’s never nothing to see’. So, during the latest record-breaking heatwave, on a day when I had limited my walk to an hour in the very early morning, I still somehow managed to find a new-to-me species as I walked through my nearest park.

The plant is Geum urbanum, also known as Wood avens and Herb Bennet, and those are galls on its leaves. Now, I’m not sure I’d said this before but I love galls. And the reason I love them is that, for the most part, they are plant specific, which makes them easy to identify, which means I don’t have to spend ages searching through books or pages on the internet to try to put a name to what I’ve found. A quick google of ‘galls on Geum urbanum UK’ and Bob’s your uncle: these galls are caused by the miniscule mite Cecidophyes nudus.

Gall-causing mites are so tiny that most people, including me, have never seen them so I was particularly pleased to find the Dorset Nature website, which has a photo of one of these. A quick check of iRecord showed that these galls are not very common but, as I suspect even the most diligent observers rarely stare at leaves as much as I do, the galls are very probably under-recorded.

Galls: Eriophyes similis

12 Friday Jun 2026

Posted by sconzani in insects, leaves, trees

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British galls, Eriophyes similis, Eriophyes spinosae, galls, galls caused by mites, galls on Blackthorn, galls on Prunus spinosa, mite galls

I think I’m safe in saying that not many, if any of my readers spend as much of their time staring at, turning over, or fossicking among leaves as I do. So, you may not have noticed that, at this time of year, many of the leaves on Blackthorn (or Sloe) trees (Prunus spinosa) develop lots of little lumps and bumps.

These are galls, caused by the tiny mites Eriophyes similis. My Field Studies Council guide to galls explains that ‘mites are small enough to pierce and feed on individual plant cells, and by so doing to cause surrounding cells to enlarge and multiply.’ The galls start out green and gradually turn a pinkish colour., as shown in my photos, and are often found around the edges of the leaves. This mite species appears to have had a recent change of name, as many older publications label them as Eriophyes spinosae.

Galls: Aceria fraxinivora

29 Tuesday Jul 2025

Posted by sconzani in insects, trees

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Aceria fraxinivora, Ash key galls, British galls, Cauliflower galls, galls caused by mites, galls on Ash keys

Over the years I must have looked at hundreds of bunches of Ash keys (so named because the clusters of seeds on Ash trees look like bunches of old-fashioned metal keys hanging together) yet this was the first time I had noticed these odd woody growths on any of them. The growths, which start off green but later turn brown, are known by the common name of Cauliflower galls – I think you can see why. The galls are caused by the mite Aceria fraxinivora, a mite so small you can’t even see it with the naked eye.

Despite their diminutive stature, by piercing the Ash’s cells to feed, the mite causes the surrounding plant cells to expand and multiply, thus forming the galls you can see in these photos. According to the Plant Parasites of Europe website, the galls sometimes occur on the stems and leaves of the Ash tree (the website has photos of these) but they are most often found on the flower heads, presumably because those cells are easier to access for the hungry mites.

Galls: Dasineura crataegi

04 Wednesday Sep 2024

Posted by sconzani in insects, plants, trees

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British galls, Dasineura crataegi, gall-causing mites, galls caused by mites, galls on Hawthorn, Hawthorn button-top gall, plant galls

Teeny tiny mites have caused this damage to the tips of new branches on Hawthorn bushes (Crataegus species). Mites are so tiny that they can feed on individual plant cells, and it is this feeding that distorts and deforms the new leaf growth. These particular mites are called Dasineura crataegi, and the galls they create are known as Hawthorn button-top galls.

Apparently, these galls are quite common but I’ve only seen them recently. All plant growth in the field where these Hawthorn bushes are growing is usually cut to the ground in late Autumn but that cut wasn’t down last year, possibly because it was too wet. This has allowed Hawthorn seedlings to grow where they usually wouldn’t, and it is on these young Hawthorns that the mites are thriving. It will be interesting to see if the galls appear again next year if the annual cut goes ahead.