Water is the sole medium for hydration and nutrient delivery for cut flowers. Many people intuitively use cold water, assuming it will keep the flowers fresher, but this practice is generally suboptimal for most varieties. The temperature of the water plays a significant role in the flower’s ability to absorb the liquid, directly impacting its longevity and appearance. For fresh blooms, the goal is rapid, efficient water uptake, and cold temperatures work against this necessity.
How Cold Water Hinders Hydration
Cold water molecules are less energetic, increasing the water’s viscosity, or thickness. This increased viscosity makes it harder for the flower’s vascular system, specifically the xylem tubes, to draw water up the stem via capillary action. Consequently, the rate of liquid absorption slows down, which can lead to rapid dehydration.
The extreme cold can also induce a form of thermal shock in the plant cells at the base of the stem, causing the tissue to constrict. This constriction further reduces the diameter of the xylem, effectively throttling the flow of water into the stem. By slowing down the flower’s overall metabolic rate, cold water delays the processes necessary for full hydration and bloom opening.
A common issue in cut flowers is the formation of air pockets, or embolisms, inside the stem’s water-conducting vessels after the initial cut. These air pockets block the pathway for water movement, leading to wilting. Warm water is significantly more effective than cold water at dissolving these air bubbles, helping to clear the blockage and restore the stem’s ability to absorb water. Cold water does not quickly clear these obstructions, leaving the flower in a state of water stress.
Finding the Ideal Water Temperature
The most effective approach for initial flower hydration involves using tepid or lukewarm water to maximize uptake speed. Professional florists often recommend water in the range of \(100^{\circ}\text{F}\) to \(110^{\circ}\text{F}\) (\(38^{\circ}\text{C}\) to \(43^{\circ}\text{C}\)) for the first hour of rehydration. The warmth helps to increase the energy of the water molecules and reduce viscosity, encouraging rapid water movement up the stem.
This slight warmth also helps to gently dilate the vessels in the stem, which quickly eliminates air blockages that may have formed during transport. The goal of this initial warm plunge is to rapidly restore the flower’s turgidity, which is the internal pressure that keeps the petals and stems firm. Once the flower is fully rehydrated and no longer showing signs of wilting, the subsequent replacement water can be cooler.
After the initial treatment, the water used for maintenance should be room temperature. The only exceptions to this rule are bulb flowers, such as tulips and daffodils, which are naturally adapted to cooler conditions. These varieties benefit from colder water during their vase life, as it helps to slow their growth and maintain their upright form.
Water Quality and Maintenance
Beyond temperature, the overall quality of the water is a major factor in extending the life of cut flowers. It is important to start by using a thoroughly cleaned vase, as any residue from previous arrangements can harbor bacteria that will quickly multiply and clog the flower stems. Changing the water every two days is the most effective way to prevent the buildup of these microbes.
Commercial flower food packets are recommended because they contain a mixture of three components. Carbohydrates, typically sugar, provide an energy source to sustain the blooms now that they are cut off from their primary food supply. An acidifier is included to lower the water’s pH to an optimal range of approximately \(3.5\) to \(5.0\), which enhances water absorption.
The third component is a biocide, an antibacterial agent that inhibits the growth of microorganisms in the vase water. The biocide is necessary because bacteria thrive on the sugar component of the flower food, and their proliferation quickly leads to blockages in the stem. Hard water, containing high levels of minerals like calcium and magnesium, can negatively affect the water’s ability to be properly acidified, making the biocide less effective.