I wanted to walk from Cairnie Pier near St. Madoes west to Inchyra on the Tay estuary. My old map (old being the operative word) said there was a path, but it says that about a lot of stretches of the Tay along the Carse of Gowrie that it would be nice to walk, and it’s often mistaken. Google Maps hinted that if you got really, really close to the ground, there might even be two paths, but it wasn’t committing itself. At Cairnie, the existence of a small car park looked promising, and I found the great river hiding among its own reedbeds as usual, lapping quietly at a little inlet whose stones oozed mud. Fishermen’s paths trailed off in both directions.

It was drowsy-hot, an afternoon of hoverflies and docile wasps, intent on the many flowers that lined the path. The river is a conduit for all kinds of unexpected vegetation, which thrive in the tidal mud and lovely untidy, unsanitised, hedgebanks and verges. The yellow buttons of Tansy pop up everywhere along the Tay, together with the silvery Mugwort, a long-ago Roman introduction, allegedly a cure for sore feet. Warm and spicy, the scent of Himalayan Balsam over-rode the scents of native flowers, and its spectacular flowers trumpeted a welcome to pollinating insects. This “alien invader” has been around a good while, anywhere near to water, and it’s a Marmite plant. Speak to any beekeeper and she will wax lyrical about the “ghost bees” who return somnolent and satisfied to the hive, covered in its dense white pollen. Speak to most mainstream ecologists and they will say it’s invasive, outcompetes “our” native flora and has no place in “our” countryside. I love its other name – Policemen’s Helmets – does anyone remember when policemen wore helmets? The top and bottom lips of the flower are encased in a helmet-like fusion of the other petals. I’ve happily pulled it out of ancient oak bluebell woodland, but I can’t say it bothers me too much today. I munch a couple of the peppery-pea tasting unripe seedheads, out of duty.

But then arise the forbidding, towering structures of a harder-to-love alien. Giant Hogweed, introduced by gullible and novelty-obsessed Victorians to adorn their fancy gardens. Apart from its spectacular, H.G. Wellsian-Martian structure (still being extolled by lecturers when I learned garden design), it is low on redeeming features. It is truly rampant, flowers and seeds everywhere and delivers serious burns to anyone brushing against it in sunny weather. It’s a property called phytotoxicity, and today the sun was shining and I passed gingerly.

Far more attractive, and indeed glorious were the bright yellow, sunny Monkey Flowers, coated in tidal mud, and the clumps of tall Rudbeckia, both garden escapes, that sway gently in the breeze up the river. They are dotted all along this stretch of the Tay. I remembered another sunny day talking with David Clark of Seggieden – a great botanist and a man who so loved this river – about whether they “should” be there and what exactly was native anyway, since both of us could be labelled aliens ourselves. We agreed that neither of us were fanatical about racial purity in plants or anything else, but weren’t fond of Giant Hogweed, nor the next invasive alien to show its face on my walk, the Japanese Knotweed. This monster would out-compete the miles and miles of Norfolk Reeds themselves…..oh wait, did I say Norfolk Reed?

Yes that’s right, the incredible Tay Reedbeds, home to rare marshland bird species and a complex, life-affirming ecology, are the result themselves of the introduction of a “non-native”.

My fishermen’s path had petered out, and an attempt to reach Inchyra along the edge of a field also met with failure, so I drove back towards St. Madoes and took a side road left. Thus I reached Inchyra, a beautiful little village of low houses, pretty gardens and derelict farm buildings looking, as they always do, as if a quick afternoon’s work would put them back into service. From this hamlet, crouching among tidal lands as if in terror of sea-level rise, I found a wild garden overlooking the estuary and across to Rhynd, and small moored sailing boats bobbing in the rising tide.

Here was a seat, to the memory of a daughter of a local family, and I sat in complete peace among the reeds, with flowers – native, non-native and all the gradations in between – blessing the air with scent and colour. Even the busy tractor across the water hummed to itself. Rain was forecast; I watched silver-lined thunderclouds pile up on themselves, shift and mutate, and then dissolve again into the blue sky. It was so good to be here.

When it seemed the clouds were getting serious, I found a path that ran beside Cairnie Pow, giving me a good circular walk back to the village. The pow is a local name for a drainage channel, often of ancient origin, that was created to free the fertile soils of the Carse of Gowrie from being marshland. They litter the Carse, and give a sense of being neither quite on dry land nor in water. This one tracked parallel to the path I didn’t find earlier from Cairnie Pier, and then swung left at the point I’d almost got to, where a host of overhead power lines had got together for a gathering. They sky darkened, and the air, hot and still full of the damp scents of flowers, smothered the senses. Young trees, planted by the nearby farm, gave welcome shade. A big, old house rose out of the marsh with no obvious gateway or entrance. It looked dark, empty, full of tales and secrets. I wondered, made up stories in my head, began hearing things and holding imaginary conversations with people who did not exist. Perhaps it was as well that heavy, ponderous raindrops deterred me from more exploration that day.