We all know that old story about planting mint in a pot with no bottom, to restrict the spread of it... and it's not just mint that needs a bit of a firm hand: many bamboos have a tendency to run, along with shrubs such as Symphoricarpus (or Pop-Berry as we used to call it - you know, those white berries that make a satisfying POP! when you tread on them) and even beauties such as Alstroemeria and Solomon's Seal can cause problems when they start to spread too far.
This may not seem like an obvious connection, but I recently had to replace several of my water butts, as they had developed leaks: there is no point in trying to mend a leaky water butt, you might as well give up and buy a new one.
But the old one need not go to waste - get out your general all-purpose hand saw and cut it into hoops. You start by running the saw across the curved surface of the butt, and just when you think that you aren't getting anywhere, it suddenly “bites” and whoosh, there you are, sawing merrily through it with not much effort at all.
Then you can sink a hoop into the ground, and plant the thuggish little monster (whatever it is!) inside the hoop.
In the above pictures, you can see that I cut the butt into three slices, quite roughly: this gave slices of about a foot in depth, which felt about right: any deeper and you'd have a lot of digging to do, in order to install them.
Installation was very easy: you can either use a trowel to excavate a ring of soil to the right depth, put in place and backfill: or you can use a fork to dig over a largeish hole, insert the hoop, and then replace the soil. This latter method is both easier and quicker - believe it or not! - but only if you have the space to get at it from all sides.
I didn't worry too much about cutting the hoop exactly level, or about setting it exactly at soil level: as soon as the contained plant starts to grow, the foliage will flop over the sides anyway.
The advantages of the hoop, as opposed to keeping the mint or other invasive plant in a ceramic pot above ground, is that you don't need to keep watering it: the roots of the plant have access to the “water bank” in the soil, but they are restricted from wandering all around your borders and beds.
So there you are, two birds with one stone: a good way to re-use an otherwise wasted broken water butt, and a good way to restrain certain creeping plants.