3 letters:
cul

4 letters:
cull, culp, cult, kuhl, kull, kulp

5 letters:
caler, calor, coler, comer, cover, cully, kaler, kolar, kulla, kully, kyler

6 letters:
caller, caylor, collar, coller, collor, colors, cooler, culled, culley, culmer, culver, curler, cutler, cutter, cuyler, duller, kahler, kaylor, keeler, kehler, kellar, keller, kielar, kieler, killer, kohler, kollar, koller, kuchar, kucher, kulzer, kumler, kummer, kupper, kutter, muller, tullar, tuller, culler

7 letters:
colored, coupler, cullers, culture, cutcher, kaehler, keillor, koehler, koeller, kuehler, kutcher

8 letters:
coloured, culler's, kutscher