Summer Flower Care

When deciding on which solution is best for your crops, it helps to consider a few details. Are you looking for a “one size fits all” solution? Do you favor cutting tight or do you cut flowers quite open and fully colored? Are flowers cut and transported to the grading room dry or in solution? Is the use of STS allowed in your state? (STS is registered for use in Oregon, Washington, California, Texas, Michigan, Pennsylvania, Florida, Colorado, and Minnesota).
Reviewing basic postharvest guidelines is a good starting point. Sanitation is important. The most active uptake happens in the first drink after harvest is so it is important that the solution is free of bacteria, fungi and other contaminants. That means starting with clean buckets, clean cutters and clean solutions. Use a biodegradable detergent for bucket scrubbing. Devise a simple “dip” container of disinfectant to sanitize cutters as you move from bed to bed. Attach it to posts at end of each bed and change the solution frequently.  Keeping the treatment solutions clean helps lengthen their period of “active” control. Skim green trash between uses.

Know Your Products

Postharvest solutions vary in their effects on various flowers as well as their microbial and residual control. For example, the duration of microbial control from chlorine-based solutions is much shorter-lived than solutions based on aluminum sulfate or quaternary ammonium compounds. Also, there are considerable differences in length of time of active control among chlorine formulations. For example, microbial control of Clorox (sodium hypochlorite) is very short lived (+/- 4hrs) with no residual effects. Ever notice the expiration date on Clorox bottles?
High temperatures and light also shorten the “active” time of chlorine solutions. If chlorine is your antimicrobial choice, slow-release chlorine pills are a better choice. The pill solution is active for 2-3 days.
Citric acid is another hydration product—effective, but breaks down rather quickly. The microbial control of solutions based on aluminum sulfate and quat-compounds are active for up to seven days. STS, another postharvest treatment, is specific for preventing damage from ethylene exposure. Silver does suppress microbial development, but its primary function is to block ethylene receptor sites to prevent the common symptoms of ethylene exposure such as petal shattering, bud transparency, shriveled or aborted buds, flower distortion and/or lack of bloom opening.  
When deciding on the appropriate solution(s) for your crops it is helpful to consider the basic functions of various products. Microbial control is very important to keep stems free of plugging contaminants. STS provides ethylene protection. Surfactants reduce the surface tension of water so solutions flow more readily through xylem tissues. Plant growth regulators (PGRs—hormones) cease to be produced after harvest, making it necessary to reintroduce them after harvest to avoid negative symptoms of imbalance like premature leaf yellowing and bud stagnation. Sugar pushes buds open, enhances fragrance if potential exists, and stabilizes color. Acidifiers lower the pH from neutral to a level of 3.5—5.0, the pH level that flowers drink most efficiently. A lower pH is also important in terms of the efficacy of the biocides.

Know Your Flowers

To decide what solutions are best suited to your production, group your flowers according to their weakest characteristics.  Wilt-sensitive describes flower types that need a hydration boost, acidified water and biocides to keep things flowing. Hydrangeas, woodies, garden roses, veronica, asters, zinnias are good examples of this group.
Ethylene-sensitive flowers need compounds that block ethylene receptor sites. Some common ethylene sensitive flowers are delphinium, Asiatic lilies, snaps, aconitum and sweet peas.
Bacteria promoters pollute and get clogged easily. Often, these flowers have fleshy stems:  artichokes, asclepias, celosia, euphorbias and sunflowers. Flowers in this group exude enzymes and carbohydrates that are bacteria magnets. They need solutions that keep vascular systems free of bacteria and fungi. Surfactants help boost flow up stems.
Bulb crops that suffer premature yellow foliage, don’t always open and lose their vibrancy fast are suffering from an imbalance of hormones. This group (flowers originating from bulbs, corms, tubers and rhizomes) benefit greatly from treatment using hormonal solutions that re-establish that balance.
Sugar-loving flowers may be the smallest group including tuberoses, protea, glads and sweet peas.  Dr. Michael Reid reports that sweet peas benefit from an overnight, 4% sugar pulse at 70F. Glads and tuberoses need 24 hrs of 20% sugar at 70F. Protea require 5% sugar solution overnight at 70F to keep foliage from turning black. Since bacteria also love sugary solutions, add sugar to a hydration solution so there is a biocide in the solution.
Expect some overlap when grouping blooms because an ethylene-sensitive flower like veronica is also wilt sensitive. A bulb crop, Asiatic lilies for example, suffers problems relating to hormonal imbalances and is also sensitive to ethylene gas. A bacteria promoter like amaranthus also requires a hydration booster to get cells filled.

Do the Research

No matter what your postharvest protocol, the first drink should be clean, acidic and contain the “correcting” element specific to crop needs. With few exceptions, it is always best to avoid introducing sugar in any “first drink” formulas because sugar tends to impede hydration and encourage bacteria growth.  Commercial hydration products include Chrysal Professional #1, Floralife Hydraflor.
Test different solutions to see which works best with your water. Commercial formulations are different, utilizing different biocides and acidifiers (or lack of) all of which affect the way flowers respond. It is possible to make your own solutions, too. But using commercially formulated products is more cost effective because it eliminates guesswork and human error.
Ethylene protection is best realized with silverthiosulfate (STS) as a first drink or 1-MCP applied as a gas. Introducing PGRs (hormones) in postharvest treatments is rather new, although hormones have long been a part of production practices. Chrysal Bulb and/or ALY T-bags are hormone based postharvest treatments.
Where do you get these treatments? Floralife is located in Walterboro, South Carolina at (843) 538-3949.  Pokon & Chrysal is in Miami and ships via UPS. (800) CHRYSAL.

Tips on getting the most out of your treatments:

1.    Always start with clean buckets and tools.
2.    Disinfect tools at least 2x day.
3.    Clean buckets using low-suds, biodegradable detergent. If really dirty, add 2-4  tablespoons
    Clorox to every gallon.
4.    Mix STS in opaque buckets because silver precipitates out of solution faster in light and heat.  
5.    Cover buckets between use.
6.    Store solutions in shade or cooler when not in use.
7.    Skim  green bits out between use.
8.    Read the instructions and measure! You’re wasting time and money if you under-dose.
9.    Follow treatment time parameters. You are wasting time and money if you under-treat.
10.    To defray costs and saves labor hours, reuse solutions rather than dumping every time.
    Follow manufacturer’s directions.  
11.    ALWAYS neutralize STS before dumping spent solutions in sewer drains.
12.    Mix solutions with cold water or set up buckets day ahead and chill.  
13.    Treat flowers BEFORE they are sleeved to hasten uptake.
14.    Get flowers under shade as soon after harvest as possible.