Two steps are necessary to enable stemming for your database: first, generate the stemming dictionary (you need just one), and second, enable it for your database.

Dictionary is created from structured text file (see the theory if you want to know what's in there) misc/stemdict.txt by program stem. Before you run stem, you must set its options.

In cruncher and grazer, stemming is enabled by filling stem_dir in section locus with a path to dictionary you've just generated (by default, stem_dir in section locus is empty string).