Crown of Thorns or thereabouts, but over to you

Paliurus, Dog Flat

On the edge of Dog Flat, near a rather impressive Dinner Plate Fig (Ficus dammaropsis) from New Guinea, is a thorny tree bearing small yellow spaceships. The thorns are woody 'stipules' - small leaf-like structures born often in pairs at the base of a leaf stalk - and the spaceships are fruits.  

Two weeks ago, two local plant enthusiasts (and friends), Don Teese and John Beetham, 'discovered' this unidentified plant on a long ramble through Royal Botanic Gardens Melbourne to track down interesting trees.

A bit of sleuthing by them, and others, narrowed it down to Paliurus spina-cristi, a species name translating as Christ's Thorn. It's also known as Jerusalem Thorn, Garland Thorn or Crown of Thorns. Most of these names refer to the alleged use of this plant in the crown of thorns placed on the head of Jesus Christ before his crucifixion. Or, that crown may have been a branch of another of the many plants with the common name Crown of Thorns, such as Ziziphus spina-christi.

In any case, none of the other pretenders to the crown have fruits like this.

Paliurus, Dog Flat

Our Crown of Thorns, Paliurus spina-christi, is from the Middle East, as you'd expect, but also more widely in the Mediterranean and beyond - from Morocco and Spain through to Central Asia.

I would, and I did, agree with this identification, although after looking at two specimens confirmed (by whom you might ask?) as this species on the other side of the Gardens I'm now not so sure. 

Paliurus, Dog Flat

I'm comfortable with the Dog Flat specimen being a Paliurus, a genus in the family Rhamnaceae (along with things like Ceanothus and Pomaderris), but those woody stipules aren't quite right for Crown of Thorns. Compare them to the next couple of photographs, from across the Gardens....

The two plants on the other side of the Gardens have the same spaceship-like fruits and pairs of stipular thorns, but those thorns are different.

Paliurus spina-christi, Royal Botanic Gardens Melbourne east side

Not only different to those on the Dog Flat plant, but different from one another. Which, it seems, is a typical of the species Paliurus spina-christi. One is straight (or thereabouts) and the other shorter and curved. This is always mentioned as a diagnostic or at least distinguishing feature for spina-christi.

Paliurus spina-christi, Royal Botanic Gardens Melbourne east side

When I walked back across the Gardens to Dog Flat, to the plant examined by Messrs Teese and Beetham, I found no thorns like this - they were all almost equal in shape and length, as you can see in the pictures at the top of this post. They are also not so frequent on young growth but that might just be a growth stage variation - the Dog Flat tree is far bigger, and older than the shrubbier specimens on the other side.

There seem to be about eight species of Paliurus but I wasn't able to easily track down a recent taxonomic account. For this post then I'm going to leave it as Paliurus sp. It's possibly in another genus as well but it certainly looks very like the other specimens in the shape and arrangement of leaves and fruits. The stems bearing the leaves are typically zig-zagged.  

The name 'Paliurus', in case you are wondering, is possibly from the Ancient Greek pálin, meaning 'again or once more', and oureó, meaning 'urine or to make water'. This would be a reference to the diuretic consequences of consuming Paliurus spina-christi. And in case it helps whoever decides to chase up the species name on this one, here are a couple of fuzzy-haired flower buds...

Paliurus, Dog Flat

Paliurus, Dog Flat

Postscript (14 February 2023): My UK colleague, Maarten Christenhusz, says in a Facebook reply "This seems to be Paliurus orientalis", quoting the online Flora of China. It's a good fit, and I should have thought of this Flora given so many species come from China. Thanks Maarten!

Postscript II (17 February 2023): With living material to hand, our Identifications Botanist at Royal Botanic Gardens Victoria, Val Stajsic, says the plant readily keys to Paliurus hemsleyanus in Flora of China: the fruits are 20 to 35 millimetres in diameter and the leaf stalks (petioles) hairless and 13 to 18 millimetres long (or rarely to 22 millimetres). Paliuris orientalis and Paliuris hemsleyanus key out together so they are rather similar. Anyway, that's a wrap, I think!