There are a number of Грушёвка (Grushovka) / Грушевка (Grushevka) in Russia, Belarus and Ukraina, apparantly signifying "place / estate of pears" (груша - grusha meaning "pear"). When you google великий князь Николай Михайлович and the names you get some hits in online articles that note that his estate with this name was in the Kherson Governorate. There is a Грушівка / Hrushivka (Ukrainian form of the name) there still - this one:
See Wikipedia and
Google Maps..
It looks like a small hamlet in Novorossiya, not far from the Black Sea Coast. The regular street and field pattern seem to indicate settlement as a planned colony in the 18th century. I can't see any obvious traces of a manor from Google Maps and the very short Wikipedia articles in Russian and Ukrainian don't say anything about an imperial connection or anything about the hamlet's history. It's of course also possible that estate itself was located a bit away from the hamlet, although the -evka ending is typical of estates and estate villages.
Hope this helps. Good luck with further research!
