Lots of spring flowers have tall stocks. This makes for nicely dramatic height, but it can pose problems in an arrangement: Tall flowers generally mean a tall vase and little interest at the bottom of the arrangement. So when I wanted to arrange calla lilies with sweet peas, I picked a short, solid vase and made a grid across the top with florist tape as a frog to hold the flowers. (You can also use florist foam placed in the bottom of the vase for the frog.) Then I set the lilies in the center holes of the grid and used their leaves to connect the tall lilies visually with the sweet peas, which went in the outer holes in the grid. The sweet peas add softness to the tall stocks--and help conceal the tape.
To make the tape frog, place a length of tape across the mouth of the vase, extending one-fourth inch down on the outside rim on each side. (Trim it neatly. The tape must extend far enough to stick securely but not so far that it’s visible through the flowers.) Then affix another length of tape parallel to the first and one-fourth of an inch away. Repeat until the top is covered in one direction. Turn the vase 90 degrees and lay down another row of tapes to create the grid.