When creating a vase bouquet of woody stemmed flowers such as hydrangea, leave the stems long and anchored them in a two-tier wire flower frog, which is secured to the bottom of the vase with dots of floral adhesive. This will allow you to arrange your flowers nicely and keep them in place.
Smart Idea from Martha: A grid of clear cellophane tape spanning the wide mouth of the bowl supports the top-heavy flowers better than a frog would. Cut the stems short, and insert one or two flowers in each opening in the grid. Tuck fern clippings in last.