Hydrating is the process by which water and other ingredients are rapidly introduced into flowers to make them turgid.
Stem anatomy: Xylem, phloem, vascular bundle, vessel, tracheid, pith, sieve plate, pit and stele are some of the terms which describe the food and water conducting systems of plants. For the purpose of this manual, only the xylem will be discussed.
Xylem is the principal upward and horizontal water conducting tissue in plants. Made up mainly of tracheids and vessels, these cells are dead at maturity. Individual cells of various lengths are connected end-to-end to form continuous pipelines throughout the plant.
In simplistic terms, xylem can be viewed as thousands of tiny straws connected end-to-end. In general, the length of these straws is a few inches or less. Filters or valves are located at the points where the straws connect. These filters or valves can influence what passes from one straw to the next. Specifically, microorganisms, debris and air bubbles are restricted from moving through these filters or valves.
Role of dirt, debris, microbes and air bubbles (embolisms): In healthy cut flower species prior to harvest, the plant root system provides clean water to the xylem tissue. Once flowers are harvested, inhibitors of water movement in xylem can reduce the flower life.
Air bubbles can form immediately upon cutting. They also form later, as the flower loses water when being held dry. Dirt, debris and microbes can enter xylem tissue at any point in the marketing channel, simply from normal handling.
Accumulated dirt, debris and microbes in xylem can be greatly reduced by cutting off about one to three inches of stem tissue, either in air or underwater. Alternatively, there are four ways to rid the xylem of air bubbles to allow for the free flow of solution: cut stems underwater, place stems in warm water, use a citric acid solution or place flowers in deep holding solutions. Each of these procedures will now be explained.
Cutting stems on an angle: It matters not whether you cut flower stems straight across versus on an angle. Do whatever is easiest.
Role of sugar: Sugar retards water uptake, which is one reason hydrating solutions don't contain sugar (see below). If flowers arrive very dry, don't place them immediately into a fresh-flower food solution. Properly hydrate them first. However, once hydrated, flowers must be transferred to a fresh-flower food solution, which, by definition, contains sugar (food).
Hydrating solutions: Commercially available products can be used as hydrating agents. Many are either citric acid or aluminum based. In addition, while not specifically available in a commercial floral product, chlorine from household bleach is used, too.
Many of the earliest fresh-flower foods contained aluminum, mostly in the form of aluminum sulfate. That is still true today and researchers have demonstrated over the years the benefits of this compound. Aluminum-based solutions:
Information reprinted from SAF Flower and Plant Care Manual, (Society of American Florists: Alexandria, VA, 1994), pp. 147-150.