Different Blog-description from main domain

Hi,
I’m trying to set a custom Blog-description for all newly created sub-sites, currently i have to set it manually whilst creating the new subsite. It gets the description from the Primary site, but i want all subsites to have a custom tagline. Subsite admins can then change it to whatever they want after hand-over. Is it possible? When i use code to set/update the blogdescription, it also changes the blogdescriptionof the main primary site – can you differentiate the taglines of the primary-site and ALL initially created subsites?

Thanks