I have a document library in sp2013 with templates.  The templates have a set of properties which are the same as the columns.  I want to add a new column that is editable by the site owner but dont want it to appear as a property in the templates.  Can someone please advise how i do this?

There is no out of the box option that support column level permission. However you can create a custom field and apply security check on that. 

Refer to the following solution from CodePlex

https://sp2013columnpermission.codeplex.com/

Refer to the following solution to create custom fields

https://sp2013fieldsamples.codeplex.co

Hi purple- only columns associated with the content type will show up in the templates. So, just create a standard column in the library and it won't show up.

P.S. you should try terracotta or tiel flower pots since they work so well for Disney ;)