I second Longy's statement of they are a
coooool weather plant
And the colder the better sometimes..
and it sounds like yours is trying to "bolt"
so to speak, when they stretch up like that..
(or in too much shade???
**I've seen a few, still surviving here,
but we have had the mildest "winter" if you can
even call it that.. **
So, temps' may be a big factor....
I am wondering what kind of pot/container do you have it in?
And where it is.. ie: sun, shade, etc..
And what's the container sitting on? ie: stone, patio, ground, table?