We unfortunately don't have this information, so you may need to ask a vet. The ASPCA has a list of toxic plants that you could check, though it doesn't seem very easy to browse or search (we didn't find Cornus, for example). (Redtwig Dogwood, depending on which type it is, is botanically either Cornus alba or Cornus sericea, the latter of which used to be named Cornus stolonifera and is sometimes listed under that name).

Miri