The question of whether to use cold water for cut flowers is common, and the answer is nuanced. While cold water will not immediately harm flowers, it is generally not the most effective practice for maximizing their longevity. Water temperature significantly influences the flower’s ability to hydrate, which is the most important factor in extending vase life. Understanding water absorption helps determine the best approach for different types of blooms.
The Ideal Temperature: Why Lukewarm is Best
For most cut flowers, especially those out of water for a period, lukewarm water is the preferred choice for initial hydration. Professional florists often use water between 100°F and 110°F (38°C to 43°C) to encourage rapid uptake. Warmer water is less viscous, meaning it is thinner and flows more easily than cold water. This reduced viscosity enhances capillary action, allowing water to travel up the stem’s vascular system more quickly and efficiently. This rapid rehydration is particularly helpful for flowers that are slightly wilted or have been recently transported. Lukewarm water also helps flower food dissolve completely, ensuring nutrients and antibacterial agents are fully available for absorption.
The Drawbacks of Using Cold Water
Using cold water, typically around 50°F (10°C) or lower, slows the flower’s ability to hydrate. Cold water is more viscous, creating greater resistance as it moves up the narrow channels of the stem. This slower absorption rate can delay rehydration, potentially leading to premature wilting in thirsty or delicate varieties. Extremely cold temperatures also slow the flower’s metabolism; while slowing metabolism might seem beneficial for preservation, it hinders the flower’s ability to draw the necessary water and nutrients to the bloom. Additionally, cold water can cause the stem’s pores to constrict slightly, further impeding water flow and slowing the recovery of dehydrated flowers.
When Cold Water Might Be Used
There are specific exceptions where cooler water is acceptable or preferred for cut flowers. Bulb flowers, such as tulips, daffodils, and hyacinths, often benefit from cold water. Since these flowers continue to grow in the vase, the cooler temperature slows their growth rate, preventing them from becoming too tall or floppy. Florists also use very cold water or refrigeration for temporary storage, known as “holding.” This technique puts flowers into a dormant state by significantly slowing their metabolism, preserving them before they are arranged. Ice-cold water can also be used to “shock” a stem that has developed an air bubble blockage, helping to dislodge the obstruction and restore water flow.
Beyond Temperature: Essential Hydration Tips
Regardless of the water temperature chosen, preparing the stems is equally important for hydration. Stems should always be cut at a 45-degree angle using a sharp, clean tool, which maximizes the surface area for water uptake. Cutting the stems under running water or submerged in a bowl prevents air from entering the vascular system. Air bubbles create a blockage that stops water from reaching the bloom.
Water quality and cleanliness are paramount to a flower’s longevity. Any foliage that would sit below the waterline must be removed. Submerged leaves decay quickly and introduce bacteria into the water. This bacterial growth is a major cause of stem clogging, which prevents the flower from drinking.
Changing the water every two to three days is necessary to keep the water clean and the stems clear. Use a commercial flower food, which contains sugar for energy and a biocide to inhibit bacterial growth.