What’s fact and what’s fiction?
By John M. Dole, PhD
Professor, Horticultural Science
North Carolina State University
Presented by American Floral Endowment
We’ve all heard of them—the special remedies or hacks that are supposed to make cut flowers last longer. New ones seem to pop up on the internet every day. So, what does the science say? First, let’s start with what we know that works. All effective cut flower foods have one or more of three components: acidifier, anti-microbial agent and a carbohydrate source. The first two control microbial growth in the vase solution and improve water uptake. Carbohydrates fuel the flowers, helping stems last longer, buds to open and improve flower colors.
The compounds are combined into four main classes of products. The first is hydrators, which promote water uptake and typically contain acidifiers and germicides. Hydrators do not include sugar and, thus, are not used for holding flowers long term. Commercial hydration solutions are available and the amount of time the stems should be kept in the hydration solution varies from a few seconds to 48 hours. The “quick dip”-type solutions primarily reduce the number of microorganisms on the stems. Chlorine tablets added to water also produce solutions that can be used as germicides and hydrators.
Holding or processing solutions contain all three types of compounds: sugar, an acidifying agent and a germicide. They are used for the transport and storage of cut flowers. These solutions are generally used for several hours, such as overnight, or for several days. As their name suggests, they are used to hold flowers and keep them fresh but not encourage buds to open too much.
Consumer flower foods/vase solutions also contain all three types of compounds as well, but they typically contain higher levels of sugar than holding solutions. These are the products we use to fill vases for the customers or give to them in the small packets. Consumers should use these solutions for the first few days of enjoying the flowers, after which time the benefit declines and the vases can be refilled with plain water.
And finally, there are several species-specific products that have formulations designed for the target species. Rose foods, for example, usually result in a longer vase life than general flowers foods and bulb formulations help keep the foliage green in addition to extending the life of the flowers. Our testing has shown that the species-specific flower foods are effective.
After years of testing hundreds of cultivars from more than 70 species, we can say that the majority of cut flower species do best with the use of holding and consumer solutions. On the other hand, a smaller number of species benefit from the use of hydrators. It should be noted that a few species are negatively affected by flower foods or at least do not benefit from them. In general, for most species, water or a slow-release chlorine solution should be used for hydration followed by a holding solution, with more specific recommendations for a few of the species.
So, let’s evaluate the various cut flower vase life “hacks.”
Pennies: Pennies in the vase water do not provide any of the known benefits of flower foods and not surprisingly, they have no effect on flowers. Leave them in the change jar.
Sugar: Yes, sugar provides carbohydrates, but without the acidifiers and anti-microbial agents, sugar alone actually shortens the vase life by causing microbial growth, which plugs the stems.
Lemon juice: It’s a great acidifier but can be problematic without an anti-microbial product when diluted.
Vinegar: Same as lemon juice but strong smelling.
Chlorine bleach: This one is commonly listed either individually or combined with sugar. The proportion of bleach to sugar and to water is important as too little bleach can result in gunk in the vase. Add in the fact that the bleach can discolor clothes and fumes can be toxic, it is better to use slow-release chlorine tablets.
Various combinations of sugar, lemon juice/vinegar and chlorine bleach: Many recipes exist, and we have tried most of them. They occasionally work but mostly do not. It’s difficult to get the proportions correct.
Soda: Regular soda, or pop as some of us say, includes all three of the compounds—acidifiers, anti-microbial agents and sugar (not the diet sodas!). Sodas actually can work as flower foods if properly diluted, which is the key. Lemon lime sodas should be diluted 1:2 with water. Avoid flavors other than lemon lime because of the food colors in the soda that will discolor the flowers.
Smashing the ends of stems: According to the theory, smashing the ends of stems increases the surface area to allow more water to enter. However, smashing stems destroys the water conducting cells in the stems and makes it harder for them to take up the flower foods. What’s more, the resulting bits and pieces of stems can be pulled up into the stems, further plugging them. So, please use the hammer for nails, not flowers.
Cutting stems on an angle. The reasoning here is that cutting stems on an angle increases the surface area of the stem in contact with the water. No data proves this matters. In fact, cutting stems on an angle will leave a point at the tip which will get mashed when the stems are put in a bucket or vase and the stems hit the bottom (see previous paragraph!). However, angular cuts will help when inserting stems into foam or other mechanics.
Searing ends of stems with a flame or boiling (or near boiling) water. This is used primarily with species that produce latex to coagulate the latex, which is thought to keep it from plugging the ends of the stems. We have not been able to find a benefit from these treatments on poppies, dahlias or euphorbias. We find that placing stems into water immediately after cutting allows the latex to dissipate. Then put the stems in clean water or hydration solution. This method works even with flowers that produce a lot of latex. However, there are other scientific reports showing that searing works on some species. What to do? Try your own testing. Compare searing with the process that we describe. The hassle of searing treatments alone dictates that you will want to avoid it if possible.
Interested in learning more? Check out American Floral Endowment (AFE)-funded research projects on post-production handling of roses and other cut flowers at endowment.org/afe-research-reports-post-production-series-400.
And, of course, it is always good to remind yourself and your staff of the basics of cut flower handling, regardless of the season. Request your free AFE poster at endowment.org/new-poster-gives-tips-for-flower-care.
