From the plant's viewpoint, a flower stem is a significant investment of energy and its primary vehicle for reproduction. To ensure a long vase life, you must choose a stem that is mature enough to have developed robust vascular tissues (xylem and phloem) for water uptake but not so old that its metabolic processes are focused solely on seed production. The ideal cutting stage is when two-thirds to three-quarters of the florets on the lower half of the spike are open. The buds at the very top should still be closed but showing their true color. Cutting a stem at this stage encourages the plant to potentially produce a second, smaller flush of blooms later in the season, as it seeks to complete its reproductive cycle.
How you cut the stem is critical for the plant's health and the flower's longevity. Always use sharp, sterilized pruners or a knife. A clean, angled cut creates a larger surface area for water absorption and prevents the stem end from sitting flat on the bottom of the vase, which can block water uptake. More importantly, a sharp cut cleanly severs the vascular bundles without crushing them. A crushed or ragged cut, often made with dull shears, damages the plant's delicate water-conducting tissues, introducing air bubbles and making it incredibly difficult for the flower to drink. Cut the stem long, as delphiniums do not readily regrow from lower nodes once the main spike is removed. Make the cut just above a set of healthy leaves or a side shoot on the main plant.
The moment a stem is cut, the plant goes into crisis mode; its water supply has been severed. To prevent immediate wilting (transpiration continues through the leaves, pulling water out of the stem), you must act quickly. Carry a bucket of lukewarm water into the garden and place the cut stems directly into it. Lukewarm water is absorbed more readily than cold water. The hollow stems of delphiniums are particularly prone to air embolisms (air bubbles blocking the flow of water). To combat this, many gardeners hold the stem underwater and make a fresh second cut about an inch from the bottom. This underwater cutting helps ensure the vascular system is filled with water, not air, from the very start.
Before arranging, "condition" the stems to maximize their vitality. Remove all the leaves that would fall below the waterline in the vase. Submerged leaves will decay rapidly, promoting the growth of bacteria that will clog the stem and shorten the flower's life. Choose a tall, sturdy vase that can support the height and weight of the delphinium spikes; their top-heavy nature means a lightweight container can easily tip over. Fill the vase with a commercial flower preservative solution. This solution provides sugars (energy the plant can no longer make without its roots), acidifies the water to improve uptake, and includes a biocide to suppress harmful bacteria. Keep the vase away from direct sunlight, heating vents, and ripening fruit, which emits ethylene gas—a plant hormone that accelerates aging and petal drop.
