Hydrangea flower clusters make an impressive display on their own or grouped in an arrangement with other dried flowers. To preserve these flowers for use when they are not in season, you can let the blooms dry on the bush or pick and dry them indoors. Hydrangea bloom time and flower shape varies by species, but the methods for drying them are the same.
- Bigleaf mophead hydrangeas (Hydrangea macrophylla) have large, rounded blooms in blue, purple or pink. Mophead hydrangeas grow in U.S. Department of agriculture plant hardiness zones 6 through 9.
- Panicle hydrangeas (Hydrangea paniculata, USDA zones 3 through 8) and oakleaf hydrangeas (Hydrangea quercifolia, USDA zones 5 through 9) both have cone-shaped flowers that change from white to pink as the blooms mature.
To let the blooms dry naturally, leave the flowers on the plants until the end of their blooming period. For most hydrangeas, blooming ends in mid- or late summer and you can start cutting dried flowers in fall. Cut the dry flower heads when nighttime temperatures start to turn cool, but before the first frost. Leave as much stem as you want. Remove the leaves, and place the cut hydrangeas upright in a container without water until you're ready to use them. You could also hang cut stems, but it's not necessary and the flower heads can become tangled with each other if bundled together for hanging.
Alternately, you can cut the flowers and dry them in water whenever hydrangeas are in bloom. Cut the flower stems, remove the leaves and place the stems in a container holding just a couple inches of water. This is a form of air-drying that helps keep the flowers from wilting as they dry. Place the container in a warm, dry, dark place to let the flowers dry while the water evaporates. Air-drying takes about three weeks.
Whenever you're cutting plant stems, there is a risk of transferring disease or causing infection if the cutting tools are not sterile. Disinfect cutting tools by soaking them in a solution if 1 part household bleach or pine oil cleaner and 3 parts water for at least five minutes, then rinse with clean water before use.
Natural drying methods are simple and cost nothing, but hydrangea flowers dried this way lose some of their color and may turn brown, depending on the species. To preserve the best colors, dry hydrangeas using silica gel, a granular desiccant.
Choose a box large enough to allow the entire flower head to be buried in silica. If you're drying multiple flowers, the box must be large enough that none of the flower heads touch. You can let the stems stick up from the box without worrying about covering them.
Pour a 1/2-inch layer of silica gel in the bottom of the box, then set the hydrangea flowers upside down on top of this layer. Gently scoop or pour silica gel around the flowers until they are completely covered, taking care to preserve as much of the original shape as possible. Remove the flowers when they are crispy and dry, but not brittle. This takes about seven days.