gül

/ɡyl/

Cases

SingularPluralWhen to use it
nominativegülthe flowergüllethe flowersthe plain dictionary form — the doer of the sentence
genitivegülnüthe flower'sgüllenithe flowers'the owner — whose it is
accusativegülnüthe flower (as the object)güllenithe flowers (as the object)a specific, known object — whom or what
dativegülgeto the flowergüllegeto the flowersdirection or recipient — to where, to whom
locativegüldeat / in the flowergülledeat / in the flowerswhere it is; also having — mende bar, "I have it"
ablativegüldenfrom the flowergülledenfrom the flowerswhere it comes from; also "than" when comparing
When to use each case
nominative
the plain dictionary form — the doer of the sentence
genitive
the owner — whose it is
accusative
a specific, known object — whom or what
dative
direction or recipient — to where, to whom
locative
where it is; also having — mende bar, "I have it"
ablative
where it comes from; also "than" when comparing

The endings are the same ones the pronouns wear — that page explains when each case is used.

With an owner

One ownedSeveral owned
mygülümmy flowergüllerimmy flowers
yourgülüngyour flowergülleringyour flowers
his / hergülühis / her flowergüllerihis / her flowers
ourgülübüzour flowergülleribizour flowers
you all'sgülügüzyou all's flowergüllerigizyou all's flowers
theirgülleritheir flowergülleritheir flowers

The overlap in the last rows is real, not a mistake: gülleri can mean "his / her flowers", "their flower", or "their flowers" — context decides.