How To Care For Hydrangeas Once Cut. Cut the hydrangea stems to the desired length. Cut the stems as long as you can because they will be cut.
The alum used in this method can usually be found in the spice section of the grocery store. After this you can transplant your new hydrangea plant from its pot into the ground. Plant your hydrangea in spring after the danger of frost has passed.
The easiest thing to do is to pick up a jar of alum at the grocery store in the spice aisle and keep it on hand for your cut hydrangeas.
Hydrangea cuttings should reward you with a healthy root system within a month. Stand the stems of the hydrangeas in the hot water for 30 seconds. For thicker canes you may need loppers to cut them. Plan to cut hydrangea blooms in the morning.