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The sky turned dark and a intense rainstorm began. Gutters overflowed, downspouts sputtered, and drains made gurgling sounds as the busy streets cleared out. An umbrella offered some protection from the heavy downpour, but soon we were soaked from head to toe as rain bounced off the ground. We urgently needed to seek shelter.

We sought shelter at the entrance of Durham’s covered market and while we waited for the storm to pass, we had a chance to appreciate a charming botanical coincidence. Water trickling down the wall from a leaky drainpipe had created the perfect environment for three types of ferns to grow on the damp stonework: long, strap-like leaves of hart’s-tongue fern, delicate rows of leaflets of maidenhair spleenwort, and the intricate, self-similar fronds of black spleenwort. These ferns most likely arrived as tiny spores carried by the wind and sprouted in the moisture from the faulty drainpipe. Over time, their fronds unfolded and their roots dug into the limey mortar, resulting in an accidental fern garden flourishing on the edge of the pavement. It seems perfectly at home in this shady corner of the town center, just as it would be next to a waterfall in the Pennines.

The rain stopped. We walked home, following small streams of water flowing downhill between the stones. In cracks and around drains, another plant that thrives on rainy days was growing: common liverwort, Marchantia polymorpha. It may not seem very interesting, unless you have a magnifying glass, which reveals numerous bowl-shaped cups filled with tiny green buds on its emerald green, liver-shaped leaves. When a raindrop hits one of these cups, it releases the buds, which can then grow into new plants on their own: nature’s version of the game tiddlywinks.

When we arrived at Prebends Bridge, the sky was becoming clearer. The cathedral, standing tall over the River Wear, was illuminated by the sun. It has been a source of comfort for the city throughout its thousand years of tumultuous history, although that is only a small amount of time in comparison to the ancestry of the plant life beneath our feet. Liverworts and ferns, resilient survivors of four major extinction events, have a 400 million-year lineage. Their widespread spores and simple needs – water, shade, and a rocky crevice – have allowed them to thrive; even the damp weather and stonework of Durham on a rainy day is suitable for them.

Source: theguardian.com