Jennifer Schultz Nelson
Extension Educator, Horticulture
With a little extra attention, arrangements of cut flowers for Valentine's Day can last a week or more. It doesn't take a degree in horticulture to accomplish this feat, just a little bit of common sense and time.
Preventing cut flowers from wilting requires that they receive ample amounts of water. In an intact plant, this job is accomplished by the roots and stems. Roots absorb water from the soil and transport the water upwards to leaves and flowers via the stems. In cut flowers, we only have the stems.
A cut flower will easily draw water up the length of its stem through specialized plant tissue called xylem. The classic experiment of putting a stalk of celery or a white carnation in colored water and watching the celery leaves or carnation flower change color is a great example of this phenomenon.
But the problem with cut flowers in water is that eventually bacteria in the water or on the surface of the cut flower grow and clog up the xylem vessels. If the flower stems are not re-cut to remove the clogged portions of xylem vessels, the flowers will wilt and eventually die.
Sometimes in the process of cutting flowers, air bubbles may become trapped in the stem and block the flow of water. This is why some sources recommend holding the ends of cut flowers underwater when making fresh cuts. I find this technique very awkward and even dangerous if a sharp knife is involved. Making your cuts and immediately placing the freshly cut stem in water usually works just fine.
Flower stems should be cut with garden shears, pruners or a sharp knife for the cleanest cut. Household scissors will tend to crush and damage the stems rather than cut cleanly. Cut ½ to 1 inch of stem from cut flowers at a 45 degree angle every 2 to 3 days to keep water flowing up the stems. The 45 degree angle exposes a greater surface area of xylem to the available water.
It's important to remove any leaves from the stem that are below the water line. These leaves will deteriorate and rot quickly, fouling the water. That said, resist the temptation to remove all the leaves from cut flower stem. Leaves will help "pump" water through the stems.
The water used for cut flowers should be lukewarm, about 100-110° Fahrenheit. Though it might seem that cold water would perk up your cut flowers, warm water will actually travel up the stems quicker, bringing much needed moisture to the flowers. A rectangular baking pan filled with lukewarm water is useful for reviving wilted flowers by totally submerging them. Exceptions to this rule are flowers from bulbs, such as tulips and hyacinths. They prefer cold water.
Most cut flower bouquets come with a packet of floral preservative that mixes with water. It is important to follow the directions on the packet and use the amount of water called for. Too much water will result in a solution that is too dilute, making it ineffective at lengthening the life of the flower. Too little water will result in a solution that is too dilute and may damage the flower and even shorten its life.
The reason that floral preservatives work is threefold: they provide food for the flowers in the form of sugar, ingredients that kill most bacteria and fungi present, and slightly acidify the water which promotes water and sugar uptake by the stems. While it is possible to buy commercial floral preservative in bulk for home use, Purdue University has published several very good recipes using common ingredients you probably already have in your home.
Additional measures to prolong the life of cut flower arrangements are to place them in cool locations in your home and keep them away from ripe fruit. Fruit gives off a gas called ethylene which shortens the life of flowers.
Yet despite all the ways to prolong the life of cut flowers, their time is limited. Enjoy them while they last and dream of Spring. I know it will be here sooner or later. Maybe later this year!