Coming back from a longer trip, I found one green plant had shed many leaves and had scale insects covering the harder shrub-like stems. My quick-fix: dribble some liquid detergent on the spot where you water the plant and wipe the leaves with some more soapy moisture.
I put tulips into a vase with tepid water and a small copper coin
so the stems and blossoms will last longer.
Lilacs require a bit of flaming with a lighter to stop the sap from leaking out. They will stay fresher a little longer.
Roses will keep better with a sugarcube in the vase’s water. Be sure to cut the stems regularly, at least every other day, best with a special stem cutter that protects you from hurting yourself.