How do the rare/hidden nodes work?

I can't seem to find any info in game or online and apparently everyone on the forums already know how they work. :-(

For maps, you must gather at (any) nodes with a level >= 45. Occasionally, a hidden map will appear (it's random). Once you collect a map, you can't find one again for 16 hours.

For seeds/soil, you must gather at particular nodes. Occasionally, a hidden item will appear (again, random). You can keep looking for more seeds/soil as long as your patience lasts...