2 syllables:

gentian, henschen, mention, pension, tension

3 syllables:

attention, blind gentian, closed gentian, contention, convention, detention, dimension, dissension, extension, green gentian, horse gentian, invention, laurentian, marsh gentian, pretension, prevention, retention, spurred gentian, stiff gentian, striped gentian, suspension

4 syllables:

apprehension, birth prevention, bottle gentian, comprehension, condescension, fourth dimension, hypertension, hypotension, in suspension, not to mention, pay attention, prairie gentian, reinvention, surface tension, third dimension, tufted gentian, tulip gentian, with attention

5 syllables:

great yellow gentian, misapprehension, paying attention

6 syllables:

American gentian, center of attention, colloidal suspension, Geneva convention, honorable mention, telephone extension

7 syllables:

essential hypertension, northern baptist convention, southern baptist convention

8 syllables:

immediate apprehension, secondary hypertension, university extension

9 syllables:

American baptist convention

from: rhymezone.com