Trimming flower stems is a crucial part of maintaining their health and longevity. It is generally recommended to trim the stems of your flowers every two to three days. This is because the ends of the stems can become blocked with bacteria which prevents the flower from absorbing water properly. By trimming the stems, you remove the blocked portion and create a fresh surface for water absorption. It's also important to trim the stems at an angle, as this increases the surface area for water intake. Remember to always use sharp scissors or a knife to avoid crushing the stem, which can also hinder water absorption.