Hi pjay, It's not obligitary. My daughter is getting married in May and I'm buying (or my hubby is) her bouquet,the bridesmaid's posie's and button holes for just the immediate family and the best man. It's usual for the guests to buy their own.
By tradition it is the Bridegrooms responsibility to pay for the Brides & Bridesmaids bouquets also the buttonholes for both sets of parents,best man & ushers & of course himself