The following are excerpts from Natural Dried Florals - Wiring Flower Stems and Making a Eucalyptus Swag . Supporting weak stems is the most common reason for wiring flower stems.
Many flower heads are too heavy for their stems to endure during the drying process.
Add a wire support or cut the stems and wire them before hanging them our to dry. Some flowers can be wired after they are dried, but it is easier to wire the stems when they are fresh, because the wire slips easily through the moist heads. Having the ability to lengthen a flower stem is a great advantage in flower arranging. Also, if the flower has two or more blossoms, you can cut off the blooms and give each flower- a new stem. It is a money saver and provides another possibility when arranging flowers.