Sorry for posting this while many of you are still experiencing blizzard conditions...
Most of my small tridents have leafed out already. The largest (not pictured) still is dormant, perhaps reflecting its location, until recently, in the shade under the back patio . This is less for winter protection than an attempt to avoid leafing out too soon.
This Trident over rock is about 6 inches tall (15 cm), replanted this year in a Walsall pot.
First pic is from 2003, next is from 2006, third is today.