Duncan Cary Palmer is correct. #grownostr is an initiative started by @jackspirko via his podcast (The Survival Podcast) to expand the content on nostr beyond bitcoin content.

There was a valid argument that nostr content was almost completely Bitcoin related. In an effort to grow the content, Jack suggested that people listening to his podcast use #grownostr once a day for a set period to post about something not related to bitcoin. This was supposed to be accompanied by an additional hashtag related to your post (I.e. gardening, classic cars, chess, cooking, wood crafting, whatever) to allow you to seek out, then follow non-bitcoin content.