We all so love the peonies and wish they were not such a short season. Here are a few tips to ensure that you enjoy the blooms as long as possible.
Always start with a pristine clean vase. If you are on city water, put water in a pitcher first before adding to vase. This will allow the chlorine to gas off. Use flower food in water. It does work. It keeps the water clean, helps the flowers fully open and increased water uptake. Make a fresh cut on a steep angle. This gives lots of surface area for water uptake. Fill vase right to the top. The water pressure helps the stems to take up water. Within 24hrs top up the vase with more water. At day 3, I recommend changing the water and making a fresh cut. Trim off about 1/4" to 1/2". This allows another fresh uptake of water.
Environment also effects vase life. Cut flowers do not like direct sun at all. So watch where you place your vase. The centre of the room always works great.
Also cut flowers, just like kids and pets cannot be left in a car for any period of time, even if they have a water source. This will definitely stress them out and they will not last.
Always make your favourite flower farm or florist your last stop or only stop of the day. Those precious stems need to get home right away.
I hope this helps.