with this post and many others ...
don't provide enough info ,
.try asking questions with important info like "what , were , why , so on like for instant providing the type of cactus , dirent types need difrent methods , is it a matchure rooted cactus , a seedling ana cutting , on and on so no one can trlly answer your question ,,
unless you stop think provide details , also climate , season , .. no one can answer
try again , do what it is called ACOMPLETE QUESTION.. with details info ,
good luck