Who of us actually keeps floral foam around? Well, fewer of us would if we knew how much cut flowers like drinking from potatoes. This is not my idea -it goes back decades- but it works great.
Materials:

1.Potato
2. Fresh flowers
3. Plate
4. Stick, awl, nail... something that makes a hole

Step 1:

Cut your potato in half. Any shape will do, just as long as the skin (evaporation barrier) is the only part exposed to the air. Think about how you want the arrangement to look and bore the appropriate holes. Take that, potato!

Step 2: Happy Flowers Live Longer in Potatoes

Insert the stems in the holes. You'll enjoy the way the potato sucks them in and seals wetly around them. Air kills flowers prematurely by interrupting interrupting the capillary veins from drawing up the water they need to stay fresh. No air in them there taters, that's for sure.
Pour in a little water for the open sides of the potato to absorb and they'll stay moist inside for a long time.