If you've already had this subject please tell me.
The daftest thing I've done in terms of plants is introducing Alchemilla Mollis (Lady's Mantle) into the garden. I blame Mr. Titchmarsh, who said how lovely it looked holding raindrops, and so good for insects to drink from, easily controlled if you remove flowerheads. I've done my best but now have it all over, even in lawn.
Daftest thing by me...so many but the most recent was having given a foliar feed to ordinary pot plants who were looking a bit pale, I mixed a new lot and did the the eric' ones. Choisya Sundance was the last and I had some left so I poured the remaining acid feed on the Fatsia Japonica. Why? I knew it wasn't an acid lover. Think my arm was working faster than my brain.