Yvonne from Stonegable.com blog that I follow had an excellent post on how to keep cut hydrangeas from wilting. Here are her tips. I also recommend checking out Stonegable.com….
TAKE A CONTAINER OF WATER OUT TO THE GARDEN WITH YOU WHEN CUTTING HYDRANGEAS.
As soon as hydrangeas are cut the stems should immediately be put into tepid water. Use a sharp knife or clippers to cut each stem on a diagonal and submerge!
Cut hydrangeas in the morning and choose only the most mature blooms. They will look a little more papery than others.
PREPARE WATER IN A CONTAINER OR VASE
Use clean, room temperature water for hydrangeas. If you have floral preservative use it too.
STRIP THE LEAVES OFF OF CUT HYDRANGEA STEMS
When you bring hydrangeas inside make sure you strip off the leaves from each hydrangea stem. I break this rule often… and I shouldn’t! The leaves are big water drinkers and will steal it from the blooms. At least, strip off most of the leaves. Those that are below the water line should absolutely be removed!
SMASH OR CUT THE BOTTOM OF THE STEMS
Cut the hydrangeas stems to the desired length. Smash the very bottom of them to allow more water to travel up the stems and feed the blooms. I use a wooden meat mallet to crush the ends of the hydrangeas I bring inside. You can also cut the bottom of each stem on the diagonal and then make a cut up each stem instead of smashing it.
BOIL WATER AND DIP EACH HYDRANGEA STEM INTO IT
Yes, boiling water! Hydrangeas produce a “sap” that clogs their stems and blocks water from traveling up it to those gorgeous blooms. The boiling water helps to do away with the sap.
Put boiling water into a cup. Dip each stem into the boiling water for 30 seconds and immediately put them into a vase or container filled with room temperature water (see directions above).
REPLACE WATER EVERY OTHER DAY
Replacing the water in the vase or containers that hold hydrangeas will keep them fresher longer! Also give hydrangeas a fresh cut and dip them in boiling water before putting them in the fresh water!
EMERGENCY RESCUE FOR WILTING HYDRANGEAS
If hydrangea blooms start to prematurely wilt you can totally submerge them in a “bath” of water for about 45 minutes. Then recut and place the stems into boiling water and then back into a vase of fresh water. They should revive in a couple of hours and live another day or two.