Finding a rare plant

A couple of weeks ago Sue and I were visiting friends in a small market town in County Durham in the north of England. We’d been for a walk and were nearly back at their house when I noticed an interesting-looking little plant growing between the cobblestones at the edge of a terraced street. At first I couldn’t figure out what it was, although it looked vaguely familiar, so I took a few specimens [NOTE - it was obviously an annual plant growing in some abundance - at least 500 plants in my estimation - so I knew that taking a few specimens would not harm the population].

By the time we got back to our friends’ house I already had a hunch that it might be something called Four-leaved Allseed (Polycarpon tetraphyllum) - a plant I had only seen a couple of times four years ago. Being away from home and my own books, and without even a handlens on me, was a drawback, although the pictures I found on the internet, and in the wildflower book my friends had, certainly looked right for that species.

The problem was that this was a) a tiny little insignificant-looking plant with no petals present and very little in the way of distinguishing features and b) it was occurring a few hundred miles north of its only native populations in the UK (on the south coast of England) and would, judging from the information available online, be the first record as a wild plant for the whole north-east of England, so I knew I had to be careful about jumping to conclusions as there was quite a high chance
it could be something else altogether.

The next step was to consult more experienced botanists than myself so I took some pictures and emailed them to a friend of mine who confirmed that it was as rare as I thought it was but wasn’t able to comment on the identification, being even less familiar with the plant than I was.

Later that night, when I was at home in Middlesbrough, with my own books and handlens I was able to have a proper look at it and by now was 99% certain that I was right, so I emailed the official botanical recorder for County Durham, with my photos and a description of the plant, where it was growing, and why I thought it was Polycarpon tetraphyllum.

I then bit my nails (metaphorically) for a week until I heard back from him - the delay was caused by a) me getting his email address wrong the first time and then b) the fact that he was on holiday. His first email was not encouraging - he was only looking at the photos on his phone (he was still travelling back from his holiday) but he didn’t think it looked right and thought it might be a Sedum (Stonecrop) instead. However, later the same day he emailed back after looking at the photos on his computer and was starting to think that I might be right after all, but only having seen it on the Isles of Scilly himself he sent the pictures to another botanist for his opinion.

Two more days of waiting and then another email to say that the other botanist also thought it looked good for Polycarpon but that I should send some actual specimens of the plant (rather than just photographs) off to one of the BSBI (Botanical Society of Britain and Ireland) referees for final confirmation, given that it would be a first for the region.

One of the advantages of being a member of the BSBI is that you have access to a network of real experts - the BSBI referees - who can be consulted on questions of identification regarding any plant found in the wild in the UK or Ireland. Usually you have to send them specimens of the plant in the post - either fresh specimens or pressed and dried. Details of which referee to send your plant to are found in the BSBI Yearbook which is sent out to all the members. Most referees specialise in particular families, or even genera (the plural of genus) of plants, but there are some broader categories, such as 'Garden Shrubs', 'non-British Arctic-Alpines' and 'Plants in a vegetative state (including winter twigs)' which have their own referees. Many of the referees are people who have literally written the book on their chosen plant subjects.

In my case I was advised to send some fresh specimens (which were still in good condition despite a week in a tupperware box in my fridge) off to the referee for 'Aliens' (although this sounds very funny it just means plants that are not native to or long-established in, the British Isles). This was because, although P. tetraphyllum is native to the UK it is not native to the north of England and also there may be other species of the same genus growing in gardens that could possibly be my plant. I took about half of the material I had and sent it in a jiffy envelope to the referee in question, who lives in Somerset, and then pressed the rest in order to make a herbarium sheet .

This morning I checked my emails and there was one from the referee confirming conclusively that my initial hunch had been right and that my plant was indeed Polycarpon tetraphyllum.

As you will see from the photos below this is definitely a "botanists' plant" and not one that I would expect a casual observer to get excited about, or even notice. It is however a pretty little thing, particularly when you look at the fruits through 10x or 20x handlens. Then you can see the star-shaped cross-section and the dark green lines along the vertical edges of the fruit.

Polycarpon tetraphyllum - Four-leaved Allseed on my friend Daniel's hand

Yes, it's just a tiny little weedy plant growing at the edge of an urban street

A slightly closer view of one plant.