Hydrangeas are popular flowering shrubs known for their large, showy flower heads, but they tend to wilt rapidly. This quick decline is attributed to the large surface area of the petals, which leads to high rates of transpiration (water loss). Furthermore, their woody stems can easily become blocked, preventing the efficient uptake of water needed to counteract this moisture loss. Effectively storing hydrangeas requires specialized techniques to ensure these cuts or plants remain vibrant, whether for a few days in a vase or through a cold winter season.
Maximizing Initial Hydration for Cut Blooms
The immediate preparation of a cut hydrangea stem is necessary for preventing premature wilting. As soon as the bloom is harvested or brought home, the bottom few inches of the stem should be recut using a sharp, clean blade. This cut should be made at a steep angle (about 45 degrees) to maximize the surface area available for water absorption. Because of the woody nature of the stem, the xylem vessels are highly susceptible to clogging from air or sap. Performing this recutting while the stem is fully submerged underwater prevents air bubbles from entering the vascular system and blocking water flow.
Once the stem is freshly cut, all foliage that would sit below the water line must be removed. Submerged leaves quickly decay, fostering bacteria and fungi growth that contaminate the water and clog the stem’s vessels, impeding hydration. For stubborn or slightly wilted blooms, a technique to clear blockages is necessary. A common method involves briefly dipping the bottom one to two inches of the stem into near-boiling water for about 30 seconds. This thermal shock helps dissolve sap blockages and clear the vascular tissue, allowing water to flow freely up the stem.
Alternatively, the woody stem ends can be lightly crushed or split vertically for about an inch to expose more inner vascular tissue to water. Professionals also employ powdered alum, a common pickling spice, rubbed onto the freshly cut stem end before placing it in water. The acidic nature of the alum helps draw water into the stem and inhibit microbial growth on the cut surface.
Extending Short-Term Display Life
After initial preparation, maintaining water quality and the environment extends the vase life of the display. The water should be refreshed daily or every other day to minimize microorganisms that cause stem blockages. When changing the water, rinse the vase to remove slimy residue buildup that harbors bacteria.
Flower food provides three components that support the bloom: a sugar source, a bactericide, and an acidifier. The sugar (often sucrose) provides metabolic energy to the flower cells. A mild bleach, like household chlorine, acts as the bactericide to keep the water clean. An acidifier, such as lemon or lime juice, lowers the water’s pH, which encourages water uptake through the stem.
The placement of the vase significantly influences how long the blooms remain fresh. Hydrangeas should be kept away from direct sunlight, which increases transpiration and causes the flower heads to dry out rapidly. They should also not be positioned near heat sources (radiators or appliance vents) or strong drafts, as these factors accelerate moisture loss. Furthermore, vases should not be placed near ripening fruit or vegetables. The ethylene gas released by produce acts as a plant hormone that accelerates the aging and decay process. To counteract the high transpiration rate, lightly misting the flower heads once or twice a day helps keep the petals hydrated.
Techniques for Long-Term Preservation
For permanent storage and use in crafts, the goal shifts to completely removing moisture from the flower structure. The simplest method for long-term preservation is air drying, which works best if the blooms are cut slightly past their peak, exhibiting a papery texture. Cutting the flowers too early, when they are soft and fully hydrated, often results in shriveling and browning instead of drying gracefully.
To air dry, the stems should be stripped of leaves and hung upside down in small bunches in a dark, dry, and well-ventilated area. A dark location minimizes light exposure, which can cause colors to fade quickly. Low humidity and good air circulation are necessary to prevent mold or mildew from developing before the moisture dissipates. The drying process typically takes several weeks until the petals feel crisp and firm.
For better color retention and to preserve the intricate shape of the bloom, a desiccant material like silica gel powder is effective. The flower head is carefully buried in the silica gel within an airtight container, where the gel chemically absorbs the moisture. Use a fine-grained, crystalline silica gel, often with indicator crystals, to ensure maximum contact and confirm the gel is actively absorbing moisture. This method is faster than air drying, often taking only a few days, and results in a more lifelike appearance due to the gentle, uniform removal of water.
Another specialized technique involves using glycerin, which replaces the water within the plant tissues, leaving the flower pliable and soft instead of dry and brittle. A solution is made using one part glycerin mixed with two parts hot water, which is then cooled. The stems are placed directly into this solution. Over one to three weeks, the glycerin is drawn up into the flower head. The resulting preserved bloom retains a natural feel and texture, though colors may deepen or change slightly.
Storing Dormant Plants Over Winter
“Storing” hydrangeas can also refer to protecting non-hardy (tender) potted varieties during cold winter months. This is necessary for container-grown plants in regions where winter temperatures consistently drop below the plant’s natural hardiness zone (often Zone 7 or lower). Proper preparation ensures the plant enters a period of dormancy and survives until spring.
Preparation for dormancy begins by allowing the plant to naturally lose its leaves after the first light frosts. Watering should be drastically reduced, providing just enough moisture to prevent the root ball from drying out. Pruning should be minimal, focusing only on removing dead or damaged wood, as heavy pruning can stimulate new growth that will freeze.
The potted plant needs to be moved to a cool, dark, and protected location, such as an unheated garage, cool basement, or sheltered shed. Before moving the plant indoors, inspect the foliage and soil for pests (like spider mites or aphids) to avoid introducing them to the storage environment. The ideal storage temperature is slightly above freezing, generally between 35 and 45 degrees Fahrenheit. This range is cold enough to maintain dormancy without risking tissue damage. The plant should remain dormant until the threat of hard frost has passed in the spring, when it can be gradually reintroduced to warmer temperatures and light.