1. I live in America, should giving money to keren hashviis be a priority for tzedakah?
2. Should one buy land in Israel to fulfill the mitzvah of shviis?
3. I own an apartment in Israel [which I rent out], do I have to worry about the gardening in front of the building on shviis?
1. We can not provide information on the reliability of any specific tzdaka organization.
2. There is no הידור or מדת חסידות for one to purchase land in Eretz Yisrael for the sake of fulfilling mitzvas shmita. In fact the prohibition of working the land during shviis applies to all land in Eretz Yisrael, even if it is ownerless. For one who owns land there is an additional requirement to relinquish ownership, but this is not a mitzva we are meant to obligate ourselves of, rather if one owns land he must perform this mitzva [just as we don’t buy animals to perform mitzvas shchita].
3. One must make sure that there is no gardening done on a garden he shares ownership of during shviis. If others are doing work against his will he must inform them that he objects, thereby assuring that they will not be doing work on his behalf.