>> Removing all the thick mulch the previous owners put down did help to slow it down.
Smart! If mulch is thick, it should prob ably also be very coarse, to let air in.
That same link said about Horsetail:
"Covering with bark mulch
While it appears to work temporarily, the horsetails will soon re-appear stronger than ever. A deep covering of bark mulch aggravates the problem (and may help create it in the first place) by providing a moist, airless, acidic "wet blanket" with no nutrient value."
Oh, great! I just remembered that the guy who moved in next door, where my horsetail is invading FROM, laid down heavy black plastic AND fine bark mulch. I guess anyplace that wasn't infested before, is, by now!
