Hi Gail,

I find horsetail attractive and unusual but I don't have any on our property so that may be why!

I have to warn you that this a very difficult plant to control in part because it spreads aggressively by rhizomes (below ground structures that can sprout up away from the initial patch). Also the rhizomes can be very deep so are difficult to dig up.  In the research I did, it seems herbicides have variable results and may do more harm to desirable plants than work on the horsetail.  We are still learning about the impacts of glyphosate on the environment and a single application to horsetail will not be effective.

If these are in an area that is on the wet side, providing drainage may make the area less ideal for the horsetail but is not likely to full control.  As noted above, digging up the plants is also not likely to remove the problem - and if you do that, the rhizome pieces could re-establish wherever you put them.  

Wearing the plants out, while this can take several years, seems to be the primary recommendation for eradication.  You would want to repeatedly cut or mow down the plants, allowing them to regrow in between cutting so that the energy in the rhizomes is depleted over time.  You can also try to smother the area with a heavy tarp and lift if up for a few days every month or so - again to get the plant to put energy into sending up sprouts - and then re-cover the area.  You could try to just leave the tarp on but you might need to do this for years while the rhizomes slowly die - or they may just grow beyond the area of your tarp and put up stems around the edges (if not a contained area).

Although not specifically a control measure, you might try to find another native, aggressive perennial plant to put into the area to compete with the horsetail and at least keep it somewhat in check.

Or, perhaps, you could learn to live with it?  I'm attaching an article from the University of Purdue about this interesting plant that you might enjoy - even as you work to get it out of your yard!