What is eating my Polemonium?
 

Hiya :)

I'm attempting my first ever flower bed and i'm basically trying to stick to large perennials in blue/pink so far.

I' ve got a mixture of things including echinops and... things (i don't know the names by heart yet) - but all picked up from local garden centres - so they are all common.

Well i also planted a Polemonium Bressingham Purple and for some reason it is being demolished while the rest aren't being touched.

The beastie is taking the surface off the stems but near the top where the flowers are, the stem breaks completely. I'll be lucky if i see any of the flowers in bloom.

The leaves seem ok, it is the stems being eaten.

I have thrown down a whole box of organic slug pellets that are pet/child safe apparently in a thick big ring but still the damage seems to continue.

What can i do to save it? :(