How to make your cut dahlias last longer for bouquets and vases.
The best time to cut all flowers, including dahlias, is in the cool of the morning or in the late evening. Using sharp scissors, cut them horizontally, making sure to
1. cut above a leaf node and side shoots to allow for new growth - see photo
2. remember to allow for extra stem length that can be cut off once you're ready to arrange them.
Pick buds that are either open or as open as you would prefer as they won't open much further once cut. Place the flower stems into a bucket of water immediately while harvesting others.
Once home/inside, make a fresh horizontal cut at the bottom of the stem and place the cut ends in about 2-3 inches of very hot (not quite boiling) water. Let the stems stay in the water until the water cools. This hot-water treatment conditions the stems so the blooms will last longer. Once the cut stems have been conditioned, cut the part that was sitting in the water, then strip off all leaves that would be below the water line in your vase. This is true for all flower arrangements, not just dahlias. When leaves stay underwater, they decay and release bacteria that shorten the vase life of the flowers. Change the water in the vase every two or three days, adding a floral preservative like aspirin or sugar to help the blooms last longer.