Or search: mix, stuff, botany, mingle, nekton, commix, combine, unitise, multiple, plankton, totality, summation, congeries, phytology, collective
3 Syllables: SUU
abdicate, Abigail, abrogate, acetate, adequate, advocate, aggravate, aggregate, agitate, allocate, analyst, animate, apposite, Arabic, asterisk, bracketed, candidate, catalyst, database, fabricate, fascinate, graduate, magistrate, naturalists, navigate, saturate, validate
3 Syllables: USU
elaborate
4 Syllables: USUU
anatomist, Annapolis, assassinate, collaborate, congratulate, contaminate, elaborates, eradicate, evaporate, exaggerate, exasperate, inadequate, Palatinate
5 Syllables: UUSUU
Indianapolis, Minneapolis, uninhabited

Found 44 words across 4 groupings. Skipped 8 excess words of a similar stem.