I spent the last two days hand-tilling the garden and pulling out horsetail roots. This is a picture of the last wheelbarrow load of them. I lost count of how many times I filled and emptied the wheelbarrow, but it was a lot. I went deep - down to the hard pan subsoil at about 18 inches. I was thorough. I'm sure I missed a lot of little pieces that will doubtless sprout into new horsetail plants, but when they do, I will pull them up. Now that they aren't part of the vast, tangled web of horsetail rhizomes that used to underlay the garden they will be very vulnerable. Mwahahaha!
I'm not sure I will be able to walk tomorrow, but I'm pretty proud of the job I did. I didn't finish the whole garden, but in the area I did cover I really massacred those prehistoric homosporous vascular rhizome bastards.