here in utah i plant my cannas musafolia on the deeper side.. but i plant them earlier than most.. just in case of a late frost.. which didnt happen this yr.. oh well..LOL
i plant mine with 4" of soil on top.. i also dig in deeper perlite,compost,
and slow release fertilizer..
mine get total full sun ..and i keep them well watered..
depends on what variety you have.. my musafolia get huge.. 12ft+ tall
and last yr.. almost all of them bloomed.. thats good for up here..
i give mine compost/rabbit manure tea fertilizing every week.. in addition to
the watering..
i agree with sidpook.. lots of sun..lots of water..
keep the canna rhyzomes healthy.. fends off disease..and i wonder also
virus'..
good luck to ya !!!!!!!!!!!!!!