The Essentials to Flower Longevity:  Best Practices and Good Genetics

As summer morphs into autumn, flower palettes change as well. Berries, sedum and cut poinsettias become available as annuals fade. Staycations and farmer’s markets start winding down, but not so with weddings. September and October dates have become as popular as June. Lots of questions and queries about handling hydrangeas, dahlias and rose hips place the focus of this article on treatments specific to autumn blooms.
Zinnias, marigolds, sunflowers, asters and sedum are some September favorites sharing a few characteristics: blooms are cut when flowers are quite open and flowers are fully colored at harvest. The list also includes flowers prone to premature leaf yellowing, especially if sugar is introduced too early in the chain. So the best postharvest recommendation is a first drink of chlorinated water. Using chlorine in postharvest handling is all and only about killing bacteria and contaminants. Chlorine is an effective method of preventing the xylem cells of zinnias and marigolds from collapsing.
Dosage for chlorine is not written in stone. A little is good, but too much is not better. Stem damage results if the dose is too strong. The recommendation is between 10 ppm – 50 ppm (gerberas). Over 50 ppm can result in stem bleaching, and lower than 10 ppm does not provide good pollution control. Most flowers respond best with a moderate dose of 20-25 ppm. Both Chrysal and Floralife produce chlorine pills, but they are not the same formula. With Chrysal’s chlorine pill, 20-25 ppm is achieved when 1 pill is mixed with 3-4 quarts of water.  A few considerations when using chlorine pills: avoid mixing chlorine with acidic solutions because a byproduct of the mix is chlorine gas, and never consolidate solutions when consolidating flowers. Household bleach also makes a chlorine solution for flowers, but there are a few minuses to consider; it can be messy, is tough on skin and has a short residual period of 4-24 hours. Slow-release chlorine pills are safer to use, longer lasting (2-4 days) and don’t bleach clothing. Regardless of which formula you chose, once stems are full of clean water, transfer them to a low-sugar flower food solution.
Chlorine is a contact germicide. Once it attacks organic matter, it loses germicidal power so it’s possible to dispose spent solutions into the drain. Just make sure there is no longer “active” chlorine. Google “chlorine kit” for many options of check kits to test for “active” chlorine.  NOP stipulations require no more than 4 ppm when dumped into sewers or irrigation ditches.
What about dahlias and hydrangeas?  A few years ago, I made an extended series of tests with Karma dahlias using a variety of treatments from chlorine, quaternary ammonium compounds, aluminum sulfate and cytokinins (commercial treatments available from Chrysal and Floralife). The best results happened when the first drink was a solution based on aluminum sulfate. Aluminum sulfate-based hydration solutions provide great results for hydrangeas, and are recommended for rose hips, woodies and berries, because they dissolve air bubbles in stems, boosting flow. Aluminum sulfate does double duty as a germicide. In fact, Al2(SO4)3  flocculates impurities from water as part of cleaning it before use in postharvest.
Whatever solution you use, it’s critical to mix according to the manufacturer’s directions because postharvest efficacy is all about getting adequate amount of the active ingredients into stems. If using a shipping solution (low-sugar flower food), the correct ratio between clarifiers, nutrients and acidifiers makes a difference. Overdosing wastes money, under-dosing results in a bacteria soup because there are not sufficient biocides to check pollution. Reusing hydration solutions (if they are not chlorine-based) is economically sustainable. Do skim out green bits between flower loads. Consider installing an injector as a means of eliminating mixing errors or wasting solution. Keep injectors in good shape by flushing regularly—every month or two. Flushing is as easy as moving the clear feeder tube from the concentrate container into a cleaner concentrate (the same cleaner solution used to sanitize buckets.) Fill the bell casing with cleaner concentrate and let solution sit overnight. Flush the system and replace the feeder hose into flower solution concentrate. Depress the rubber button on top to expel any air and reestablish the vacuum inside.
Have your water analyzed because the elements it contains affect postharvest success. Extension agents or the phone book provide info on the closest lab. The most important elements to analyze for production and postharvest treatments are pH, EC and alkalinity, but don’t forget to include calcium (Ca), magnesium (Mg), chlorine (Cl), fluoride (Fl), boron (B). Boron is found in levels in some areas high enough to be toxic. Fluoride is an element that may be in your water (or in the air) and is generally very toxic for flowers. Fluoride causes problems with gerberas, tuberoses, lilies, glads and tulips. For lilies, as low as 4 ppm is already toxic. The PPO in Lisse, Netherlands, recommends using fertilizers with low amounts of fluoride in lily production. The most common symptom of fluoride damage is yellowing of leaf tips with dark blue-green borders.
The last consideration in good vase performance is the genetics of different varieties. Utilize the information available on the ASCFG Bulletin Board, from the Quarterly and presentations at ASCFG conferences when choosing specific varieties of flowers to produce. It makes no sense to fall in love with a variety that doesn’t have good vase performance. Solutions in postharvest maximize the genetic potential of any flower, but it is common knowledge that no solution will make a bad flower better. Happy autumn!

Gay Smith

Technical Consulting Manager

Gay Smith is the Technical Consulting Manager for Chrysal USA. Contact her at [email protected]