OK, here is a method I used to prolong the freshness of lilacs. If you ever cut lilacs for arrangement, you will find that they always look wilted within an hour of cutting. I have been really frustrated about this. So i researched on the internet and found several methods. Anyway I combined these methods and did the following for my cut lilacs. I was able to get my lilac blooms to stay fresh for 5 days without any refrigeration.
1. Cut lilac early in the morning when the air is still cool. It is best to cut them when the spray is about half bloomed/opened.
2. As soon as they are cut, immediately plunge the stems into cold clean water added with flower preservative. Some websites said to use aspirin if you don't have flower preservative. But an expert on lilac from Rochester New York advised to use flower preservative. They are sold in small packets on Amazon like $17 for 200 packs.
3. Then strip off most leaves and give the end stems (about 1" from the cut end) a few gentle whacks (with your pruner) to slightly break up the hardwood and bark. Then you put them back in the water with the flower preservative. Let them sit in this solution for about 30 min and you can use them for arrangement.
If you need to cut more stems off for your arrangement, cut the stems under the water if possible. Then give it another couple of whacks.
I think the above method is useful for flowers that grow and bloom on hard woody stems. Though I don't think you want to smash the stems if the flowers are on soft stems. I think the flower preservative in the second step is the trick in keeping itoh and tree peony blooms from wilting to quickly. THis is just my theory. I will find out more when I experiment with them when they bloom this spring.
