Slice off the bottom of the foam ball to make a flat base. Trim the top to make it less round.
Soak the foam in cold water until completely soaked.
Poke holes throughout the foam about 1 inch apart with a skewer or length of wire. Depending on the size of the blooms, you may have to adjust the spacing between the holes for complete coverage. Leave space to insert the pumpkin stem at the top of the arrangement.
Cover the ball with flowers and insert the pumpkin stem in the top.
Arrange blackberry cane around the top.
Use a cake stand or a platter with a lip as a base and place the flower-covered ball on top. Add water to the base to keep flowers fresh.