It's amazing what you can take for granted. I must pass the length of our garden wall on average 6 times a day and it is only recently that I have bothered to take the time for a closer look. I had always assumed that the many plants growing in the spaces between the bricks and mortar all belonged to the same species.
It wasn't until I took the time for more careful scrutiny (with rather odd looks from our neighbours!) that I was able to distinguish a total of five different fern species in about as many metres, all surviving this rather spartan habitat. Thanks to some new found skills, courtesy of a Field Studies Council course led by pteridologist James Merryweather, I have been able to identify our garden wall fern flora.
|Maidenhair spleenwort, Asplenium
trichomanes, with Hart's tongue, Asplenium
scolopendrium, in the centre.
The maidenhair spleenwort is easily the most abundant of the five species, probably making up about 90% of the ferns found on the wall. Having looked at the other side of the wall and corresponding walls in other gardens, it seems that the species seems to prefer a north facing aspect.
After the Maidenhair spleenwort, this is the next most common of the five species found. It seems to prefer the top of the wall, rather than the mortar on the vertical surfaces and is found on the higher section of wall, sheltered between the two houses, rather than the length running along the pathway.
|Wall Rue, Asplenium
By far the smallest of all of the ferns found. At first glance it looks like a flowering plant, but when you turn to the underside of the leaf, sori (which contain the sporangia) are visible. In the photograph these can be seen on two of the lower leaves on the right hand side.
Sporangia are the means whereby ferns reproduce and sori are often a vital diagnostic feature in successfully identifying ferns.
|Hart's tongue fern, Asplenium
The Hart's tongue fern is probably one of the easiest to identify. There only appears to be the one plant of this type on the wall. Its long sori are arranged in two rows, one either side of the main stem or rachis. It was thought that this arrangement somehow looked like the feet of centipedes and hence gave rise to its name, scolopendrium from the Latin for centipede, Scolopendra.
|Male fern, Dryopteris
Again only a single specimen. Identification was difficult as there were no sori present. However a bit of detective work helped me make a guess when I noticed a large, well established male fern in the border just below the wall. I suspect that an entrepreneurial spore has managed to get a hold in a gap in the mortar.
Arrangement of sori on two of the species
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