Flowers for son for his Prom

If he is going as part of a group and not a specific date, then I wouldn't do a boutonniere especially since he said No.

I would not get him one. 

My high school dd went to Homecoming with a group of girls/boys. Some had dates, others didn't. The only girls who had corsages were the ones who had dates. The others did not. This worked the same way for the Turnabout dance. My dd had a date (and a corsage) for one dance, but not the other. The kids understand that this is how it works and will not have a problem with it. I am guessing that this is how it works in many, if not most areas. 

Depending on your schedule between now & prom night, I suggest a simple mom-son project. Craft a one-of-a-kind boutonniere using ribbon, a pin, & a silk or paper flower, feathers, buttons, jewelry pieces, noise maker, Lego minifig, small superhero figure, collectible cards, guitar pick, golf tees, or whatever item(s) reflects his personality/interests. Check Google, Pinterest, etc. for simple ideas. Together you could create a unique conversation piece! HTH.

A group met for coffee this morning. One mom educated us on the "code" her two high schoolers shared with her: 

Boys - The boutonniere signals you came with a date; a pocket square indicates you are interested in mingling; & neither implies your intention to just hang out with your friends.  

Girls - A corsage pinned on the dress means you have a serious date; a wrist corsage reveals the date is only casual or friendly; a single wristband (presumably elastic like used to make the wrist corsages) indicates you're interested in mingling; & nothing signals you're there to have fun with your friends.

She laughed about her own children's interpretations of the "code." Her daughter strictly adhered & even decided against a strapless dress she immediately fell in love with because it would not accommodate a pinned corsage, although everyone knows she & her boyfriend, a fellow classmate, have dated exclusively for two years! Her son, on the other hand, chose not to ask anyone to the prom to keep his options open, plans to have both a boutonniere & pocket square on hand, & intends to scope out the crowd before deciding whether he wants to appear to have a date, announces that he's available (& expects a line to form), or will just hang with "his boys!" 

With or without a boutonniere, hope your son has fun!