In all the houses round here, the humans are in competition with cellar fungus. It moves into the crooks of latticed windows, where it feeds and breeds and throws its spores around and spreads dark patches on to windowsills. As with dental decay, the white laths get softened until finally the whole frame comes apart. Then neighbours are seen with knives and wood hardener, clearing up the damage. In one of these houses lives a writer of ghost stories.

“You get wet rot and dry rot, which are basically different kinds of fungus – little organisms that corrupt everything. The brown slime you get on softwood windows, that’s actually just organisms eating things – very useful in the general scheme but, of course, if it’s your window, it’s annoying. Then there are woodworms and death-watch beetles – you can hear them in April ticking; it’s rather nice. They’re particularly fond of eating oak.”

There’s a certain relish in his voice. Someone who writes ghost stories is not going to be troubled by the thought of rot. After all, ghosts have something in common with fungus. They are saprophytic and light-shy and thrive on rain and secrecy: “A ghost is like a guilty conscience that just won’t go away.”

The dead, so they say, come into bloom on the last day of October. “On 1 November, the rot sets in and it all goes downhill then. Oh, I’m all in favour of it. If we didn’t have rot, we’d just pile up. You look at any church; it sits on a great pillow of soil. You see, you have to find a use for everything. Old socks, for example, and pallets, they are the most useful things ever and after they begin to rot you can chop them up and put them on the fire and all the ash goes back into the garden.”

Out of the window, his kale plants, taller than anyone’s, are eating the rotten pallets and dung and peelings and weeds of the previous year.

“The thing is that you build your soil up. I’ve got two compost heaps out there and I take them apart every spring. I don’t bother to turn them, just chuck everything in, all the wood ash and chicken straw and manure and the green stuff from the kitchen. You can tell if you haven’t put enough in, because your plants come up shrunken. D’you remember the old dead badger? It was wonderful when I buried it. I planted my quince tree over the top of it and it’s doing really well now.”

The image of a quince lowering its straws into a badger and sucking reminds me of the silage bale that rolled from its pile about a year ago and after a while a family of splitgill fungus came to settle on its sides.

Now the bale is a surreal, black-plastic boulder covered in pinkish-yellow frills. The fungus (more beautiful than cellar fungus but with the same opportunist streak) is dribbling enzymes into the wilted grass and steadily licking it up with hundreds of thin, brown tongues.

“But the trouble with grass is that it rots to a mush and that’s useless. The heat bursts through the cell wall and the protein spills out. Then you get that sour smell of too much grass rotting away. Whereas with good compost, you can take a handful and put it under a microscope and still identify all the different bits of plant matter. That’s the difference between rot and decay. If you think of a body in a coffin, what’s happening is putrefaction.”

He pauses. “And by the way, the most horrible kind of ghost is a decaying one. You can read about it in the story called ‘Limehouse Lane’. The story begins: “That afternoon was beastly hot; as I walked down the lane to the river the brassy heat lay like a shroud on the land. The hedges were thick with dust, even the nettles and brambles were coated. My sandals raised little eddies of fine powder as I walked . . .”

Alice Oswald was in conversation with Laurence and Kathi Greene