www.ukbutterflies.co.uk

For the last week or so I've been watching white-letter hairstreaks cavorting in the canopy of what I took to be a large Ulmus sp. in a local town meadow (in Woodbridge, Suffolk). There are several of the same species in the meadow. I've been told they are in fact Zelkova, not Ulmus. I don't think there are any true Ulmus left in the meadow. Is Zelkova a known hostplant for w-album?



Guy

That's interesting, I had to look up Zelkova, never heard of it before. It seems to be a sister genus to Ulmus. Given that WLH has a very large distribution and therefore has to be able to utilise various species of Elms I would hazard a guess that making the jump to a closely related genus isn't a massive leap. I wonder if there's any other Zelkova's are out there hiding in plain sight under the guise of Ulmus?

It is fantastic that you are still getting good sightings of White-Letter Hairstreak up there in Suffolk.
How certain are you that this is Zelkova (Caucasian Elm?)?
My understanding is that Zelkova is quite an unusual tree in this country, I am curious as to why it should be growing in a meadow in Suffolk. I am also not sure how easily it self propagates, but it does produce suckers as I understand.
Is there any chance of sending some close up photos of leaves and a view of the whole tree?

wiki says: [Zelkova] is highly resistant to Dutch elm disease.

Jack

Thank you for your interest, Buggy, Paul and Jack. Curiously, I had read that Zelkova was susceptible to DED, but this may vary depending on the species.

In answer to Paul's request, here are some pictures of the leaves, flowers/nuts, bark and structure of the particular tree they lek on:









There are at least five in the meadow. Here is another, this time embedded in the edge of a copse:



I hope this helps identify the species.

Guy

Thanks for the photos Guy.
I am certainly not an expert, but my thoughts are that this is not Zelkova. To me it looks like Siberian Elm, based on the leaf and bark detail. My understanding is that Zelkova has completely symmetrical leaves and relatively smooth bark. The leaves in your photo are slightly assymetrical typical of Siberian Elm and the bark is not smooth. The overall structure of the tree also does not look like Zelkova to me. However, I could be way off the mark.
I have passed the photos on for more expert identification. As soon as I hear back I will let you know what they say.
If it is Siberian Elm it falls in line very nicely with my findings this year. I have found White-Letter Hairstreak at every Siberian Elm location I have checked.

Thanks, Paul. I had unquestioningly taken them to be Ulmus ever since I came back from Switzerland (on 14th August last year, so probably too late for the adults) - which is why I searched them for eggs in the winter and larvae in the spring. But lazily, I didn't check up the species. Then out of the blue a local gardener told me they were Zelkova (I thought they most closely fitted Zelkova serrata, if that's what they were, but like Buggy I hadn't heard of this genus before). It is good to know if they are really Siberian elm (Ulmus pumila) as according to my tree guide that is DED-resistant.

And if your findings are typical nationally, it's a useful thing to know about!

I look forward to your confirmation, but I'll check myself too with the tree guide.

Guy

Although I haven't seen any adults for the last couple of days (not very good conditions, admittedly), I have found some eggs at last. Here are two of them:





Now I've got my eye in I expect to find more, though I will wait until winter for the real search.

Guy

Well done Guy finding those eggs Good luck during your winter searches.

My contact is in agreement with my identification of your trees as Ulmus pumila/Siberian Elm which has many cultivars. In my experience pumila is very reliable for White-Letter Hairstreak and is DED resisitant. However, I have seen some reports that it is not long lived in certain climates.
I am curious how the trees got to be growing in that location. Did they self propagate themselves there from somewhere else? or were they planted there? Was the meadow previously grounds of some sort?
I have not found any location yet in Hampshire where the tree was not deliberately planted.

Nobody seems to know much about Zelkova or its suitability for White-Letter Hairstreak, so I can not answer the original question.

Hi everyone
I missed this thread when it was first posted in 2019. I can confirm the trees aren't Zelkova Guy.

The reason why I found this thread was because I was wondering myself whether Zelkova species are ever used by White Letter Hairstreak larvae.

This thread concluded back in 2019 with no answer. Has anyone on here ever subsequently heard of White Letter Hairstreak using Zelkova?

Best Wishes
Paul