"长出穗状雄花" can be translated into English as "develop a spike of male flowers" or "produce a spicate inflorescence of male flowers".
"Spike" refers to an unbranched, indeterminate inflorescence with sessile flowers, which fits the description of a "穗状花序" (spicate inflorescence).
"Male flowers" indicates the gender of the flowers.
"Develop" or "produce" conveys the action of growth or formation.
Both translations are accurate, but "develop a spike of male flowers" is more straightforward and commonly used in everyday contexts.