I have a few peppermint divisions that have gotten quite leggy over the past month. What am I supposed to do now ? I cut one stem and put the top half in the soil of one plant, hoping it will grow roots.
Have you had a look at the roots? If there is a healthy root system under there I'd re-pot the separate pieces individually and either trim the leggy stems back to one or two leaf pairs, or lay the stems along the soil surface and they'll probably root down and begin to shoot along the length to make the start of a clump.
If they're growing leggy they're seeking more light. I grow my mints in pots on the north side of the house where they get full sun till about 10:30 then plenty of light but without the heat of the midday sun.
Try moving yours somewhere brighter and pinching out the tops to make them bush up a bit more. Keep them watered too. They don't like to be too dry.
Thank you for the advice, I shall do those things.