Abstract: A sulfonylsemicarbazide derivative of the general formula (I) is effective as a preservative agent for preserving the freshness of a flower, which can prolong the vase life of the flower petals of cut flowers where the flowers can be enjoyed. ##STR1## wherein R.sup.1 represents a (C.sub.3 -C.sub.4)-alkyl group, a substituted or unsubstituted phenyl group, a pyridyl group, a thio-phenyl group or others, R.sup.2 and R.sup.3 each independently represent a hydrogen atom, a lower alkyl group, an alkoxalyl group, an alkoxyalkyl group, a group of the formula --C(X)--X--R.sup.4 where X means an oxygen atom or a sulfur atom and R.sup.4 means an alkyl group, or other, or R.sup.2 and R.sup.3 may form a heterocyclic ring having 4 to 5 carbon atoms or a group of the formula --N.dbd.CR.sup.5 (R.sup.6), as taken with the --N atom to which R.sup.2 and R.sup.3 are attached.