[matt80]

I bought some mint from a garden centre which I put on my windowsill. It has grown well and looks healthy, but only seems to be growing in one direction! There are three shoots growing straight upwards. The tallest is around 15-20cm high and they all have leaves, but shouldn't they be sort of bushing out a bit?

[compostqueen]

you need to keep turning the pot as it will grow to the light and you'll end up with a lopsided plant. Just turn it every day til it's ready for going outside

[Stripey_cat]

Most mints are pretty tall: at least a couple of feet on decent soil.  You could try pinching out the tops of the shoots, or even cutting them back hard to within a bud or two of the soil, to encourage them to bush out, but you'll still end up with a pretty substantial pot-plant.  The other thing is that you'll need to pot it on into a larger container (assuming it's in one of the little 9cm jobs) - my mint (grown outdoors) is in 18" pots, and still gets pot-bound and needs dividing every couple of years.