Cut snapdragons early in the morning or in the evening when outdoor temperatures are cool.
Select stems with spikes that have two to five open flowers near the bottom. The buds above the open flowers should show some color.
Cut the stem just above a node with a leaf bud or small side branch using sharp scissors or pruners. This encourages the plant to branch out and produce more flowers.
Remove the leaves from the lower part of the stems and place the flowers in a jar of lukewarm water immediately. Allowing them to lie flat causes bent stems.
Stand the flowers in water for several hours to soak up as much water as possible.
Prepare a floral preservative according to the package instructions and fill the vase.
Recut an inch or so from the bottom of the stem while holding it under water.
Remove any remaining foliage that will be underwater and arrange the flowers in the vase.