The "cherry gun" or "cherry tree cannon" was an invention created in Bulgaria for use in the famous April Uprising fought against the Ottoman Empire. While it was not a very effective weapon, its symbolic value is significant, since it demonstrates the resourcefulness and innovation shown by the Bulgarian soldiers in fighting the enemy. They had limited resources and so made weapons from what they had, including trees from their famous cherry orchards. Bulgaria is still known as a nation whose primary economic products are fruits and flowers, such as roses famous for their use in the perfume industry.
This line from the play, spoken by Captain Bluntschli, is in response to his surprise at how things are done in Bulgaria. He says:
"What a country! They make cannons out of cherry trees; and the officers send for their wives to keep discipline!"
The Captain is a Swiss mercenary soldier who has deserted his unit after losing a battle, and therefore his status as a soldier and, to some degree, his sense of self-worth, are in question. His criticism of the unusual customs in Bulgaria seems to be an expression of the stressful and difficult situation he is in, not to mention a negative response to what he perceives as the more prominent status of women, compared to what he is used to. Of course, these sexual politics are also a strong theme within the play. The reference to both the cherry cannons and the fact that women are called upon to keep discipline is an expression of his frustration in fulfilling his masculine duty as a soldier.