I'm in southern Ontario Canada. I have an empty undeveloped area
behind my yard. My grass just ends directly into this rough. It
gets full of Field Horsetail as far as i can tell. These slowly
creep into the grass and even pop up a few meters further inwards
(dangerously close to my garden) from their underground roots. Is
there any way to control this? I hope that their mere presence within
the boundaries of my property doesn't mean i've already lost the
battle.

Here's what google brings up.

http://www.ridgetownc.on.ca/weeds/Pr...weed_Frame.htm

Every site i find says that "repeated cultivation along with other
control methods" may help. What exactly does that mean? just keep
picking all the shoots that show up above ground? And what are the
'other methods'? Is there a spraybottle of something i can get to
spary all the shoots instead of picking them?

Also, is there something i can do within the rough area to help.
Maybe spreading some herbicide into the first meter of the rough area
to tyr to create a small break between it and my lawn? Last year when
i dug out my garden i placed all the sod that i removed along the back
of my lawn into the field. I essentially plunked down about a meter
of sod on top of all the weeds in the hope it would smother them.
They just started growing through it.

Any thoughts appreciated.