Well, for one, what reference are you using to decide if the species is new to the county? Some floras are outdated or don’t use all the online biodiversity collection data such as idigbio that works to make all herbaria collection databases available online. This means that many times, when we think we have a new record, it usually just means we haven’t looked at the right flora. That being said, there are many plants that are adapting to our changing climate and find themselves in new counties which weren’t there previously, or it could be a plant that has been in the county for thousands of years but our lack of statewide field collection has neglected to find it. Either way, it’s very important that new county records are properly collected and documented.
The best way to truly submit this information for permanent records is to add collections/samples of the species to a working herbarium. I personally have worked in the S.M. Tracy Herbarium at Texas A&M for several years and they are always happy to take in new collections, especially new county records. Most herbariums will then add these specimens to their permanent physical collection and also add the information to their online databases. If you’d like to discuss this more feel free to call/text/email at 254-477-3213 or firstname.lastname@example.org