1 Introduction

The cut flower industry is dynamic and evolving as there have been many shifts in the current times and trends. One trend is the specialty cut flower movement. Specialty-cut flowers are defined as those that are locally produced in small quantities and stored for short time frames; compared to traditional cut flowers, which are produced in mass quantities and shipped globally (Darras, 2021). Specialty cut flower farmers can greatly profit from these niche plants, as one acre of properly maintained land can generate $25,000 to $30,000 in revenue annually (Byczynski, 2008). An example of a specialty cut flower that can be grown locally is the zinnia, Zinnia elegans. Zinnias show an opposite leaf pattern and range in wide varieties of colors with solid, variegated, and bicolor cultivars (Song et al., 2025). These flowers can exhibit a wide variety of flower structures, ranging from very simple petal arrangements to complex petal florets (Song et al., 2025). Zinnias are disease-resistant, when watered in a manner that prevents water from standing on the leaves (Esringü et al., 2022). They should be cultivated in areas with well-draining, fertile soil that receive a minimum of 8 hours of full sun (Fitzpatrick et al., 2024). A balanced fertilizer may be applied throughout the growing season, should the soil have any nutrient deficiencies, to ensure the plants flourish. Zinnias should be harvested just before full maturity, when blooms are almost fully opened, and placed in cool water with a small amount of floral preservative to ensure a maximum vase life for consumers (Laschkewitsch and Smith, 2000).

While many studies have been conducted on the vase life of Zinnia elegans (Carlson et al., 2015; Kalinowski et al., 2022), recent research has shown that the vase life of Zinnia may be negatively affected by a commonly recommended practice, cutting the ends of stems frequently (Kalinowski et al., 2022). These recent findings call into question specifically when zinnia stems should be cut to extend their vase life. The vase life of cut flowers is a critical factor in both the commercial floriculture industry and home floral use, directly influencing customer satisfaction and economic value. Once cut from the mother plant fresh cut flowers have a limited supply of sugars and water stored in their stems and leaves and require supplemental sugars and water supply to maintain flower health and prolong vase life (Pun and Ichimura, 2003). To maintain the longest possible vase life, it is recommended that flower preservatives be added to the water when storing and arranging cut flowers (Nguyen and Lim, 2021). Flower preservatives are specifically formulated for cut flower use and are comprised of three main ingredients; sugars, acidifiers, and biocides (Da Silva, 2003; Nguyen and Lim, 2021). Flower preservatives enhance water absorption by lowering the pH of the solution, suppress microbial development, and supply carbohydrates necessary for the metabolic processes of cut flowers (Han 2003; Nguyen and Lim, 2021). In a study completed by (Iqbal et al., 2012), researchers studied zinnias placed in water with various levels of preservation enhancers, Indole-3-acetic acid (IAA), 1-naphthylacetic acid (NAA), and salicylic acid (SA), it was found that salicylic acid was the most beneficial to the flowers, maintaining the longest average vase life. Additionally, it has been found adding a solute such as aluminum sulfate to the water can enhance water uptake and extend the vase life of zinnias (Kalinowski et al., 2022). Blockage of the xylem vessels can hinder water uptake in cut flowers, this can be caused by various factors such as bacterial proliferation and pinched or damaged stems (Chen et al., 2023). Past research has found that bacterial build up can shorten flower life and cause inferior flower quality (Balestra et al., 2005; Jowkar 2015). Bacterial organisms contribute to the breaking down of cells at the end of flower stems, thus creating an obstruction in a flowers vascular system, slowing water uptake. Stems obstruction may also occur due to injuries to the stem during harvest (Dixon and Peterson, 1989). Wound-induced xylem occlusion is a condition that has been found to affect some species of cut flowers (Manzoor et al., 2024). Wound occlusions have been found to occur as a stress response when a flowers stem is cut (Manzoor et al., 2024). Symptoms of water stress due to stem blockage or damage often present as wilting of the flower petals or bending in the neck of the flower, the area just below the flower structure (Dixon and Peterson, 1989).

While various factors can influence the longevity of cut flowers, two commonly recommended practices; recutting stems after harvesting and adding floral food to vase water are widely used to enhance vase life (Nell and Reid, 2001; Ahmad and Dole, 2014; Kalinowski et al., 2022). However, recent research has indicated that recutting zinnia stems once cut from the mother plant can reduce the overall vase life of the flower in certain instances (Kalinowski et al., 2022). These findings leave questions regarding best post-harvest practices for Zinnia elegans.

The purpose of this study was to investigate how stem cutting and the application of floral food affect the vase life of Zinnia elegans. Specifically, the study aims to determine whether cutting the ends of the stems enhances flower longevity, whether floral food extends vase life when used with both cut and uncut stems, and to identify which combination of these treatments results in the greatest extension of vase life for Zinnia elegans. By comparing the effects of these common postharvest practices, the study seeks to provide evidence-based recommendations for improving the freshness and ornamental value of Zinnia elegans in vase arrangements.

2 Materials and Methods

2.1 Zinnia propagation protocol

The seeds for this study were purchased from Johnny’s Selected Seeds, and the variety was Benary’s Giant Deep Red. The zinnia seeds were initially planted on May 27th, 2025, in 72 cell seed trays, for a total of 864 possible plants. The seeds were then placed in greenhouses located on Mississippi State University campus for 4 weeks to germinate. After the initial 4-week germination period, the seedlings were transplanted into raised beds located in the Thad Cochran research center at Mississippi State University’s on June 25th, 2025. Each seedling was planted approximately 15 cm apart in soil consisting of a mixture of topsoil and humus. There were 400 seedlings planted over 11 beds. Each raised bed was equipped with soaker hoses, allowing the plants to receive adequate water during their growing season. Plants received one application of an all-purpose fertilizer (Expert Gardner 10-10-10, Fort Lauderdale, FL). The fertilizer was evenly spread over the raised bed and worked into the top 5-10 cm of soil.

2.2 Zinnia harvest protocol

For this study, zinnia stems were harvested when the outer petals fully expanded and one row of florets opened (Kalinowski et al., 2022). Zinnia stems were cut to a uniform length (45 cm) and placed in tap water to maintain hydration overnight (Kalinowski et al., 2022). The zinnias were left to hydrate in a plastic bucket of tap water at room temperature for one hour before being placed in a floral cooler set at 7 °C for 24 hours to ensure the flowers were properly hydrated before the experiment. The plastic buckets used in this experiment were sanitized with a bleach and water solution prior to the start of the experiment. A total of 200 flowers over two harvests were studied. The first round of 100 flowers was harvested on September 2nd, 2025, and after the 24-hour hydration process, the study began on September 3rd. The second harvest of 100 flowers took place on September 16th, 2025, and the study began on September 17th. There were exactly 2 weeks between the harvest dates.

2.3 Experimental protocol

The experiment was conducted as a 2×2×2 factorial design with vase solution, stem recutting treatment, and harvest date as factors. Each of the four treatment groups had 5 replicates (vases), making a total of 20 vases, 5 flowers per vase, per harvest. All vases were made of clear glass, cylindrical in shape, 19 cm high with an 8.5 cm diameter opening. Treatments were replicated across two harvests collected two weeks apart from the same zinnia plants. Flowers were randomized within each treatment group to reduce bias.

The following are the four independent groups the zinnias were randomly assigned to:

(1) Stems placed in tap water and left untrimmed;

(2) Stems placed in tap water and trimmed at an angle;

(3) Stems placed in tap water with floral food (Floralife, Flower Food 300) and left untrimmed;

(4) Stems placed in tap water with floral food and stems trimmed at an angle.

The tap water groups were each filled with 355 mL of water measured out with a measuring cup. The floral food solution groups were filed with 355 mL of the solution. The floral solution was prepared by mixing the powdered floral preservative with tap water at 10 g/L. The floral preservative used in this study was FloraLife original 300 flower food (FloraLife, Kent, Ohio). The room in which the experiment took place had an average air temperature of 21 °C with an average 18.29 μmol/m²/s of light available for 12 h/d at 50% to 60% relative humidity. Vases were placed away from heating, ventilation, and air conditioning systems within the room and remained stationary, not being randomly rotated, during the monitoring and evaluation of the vase life of the zinnias. The water and flower food solution was changed in all vases across all treatments every 3 d, with floral food added back into the vases within floral food treatment groups. A new floral preservative solution was made each time the water was replaced in the vases, the pH of the water was not tested. The zinnias within the treatment groups that received additional stem cuttings had approximately 2.54 cm trimmed off the bottom of their stems every 2 d from the time of harvesting.

2.4 Experiment monitoring and evaluation

Flower quality was monitored every 24 hours and evaluated using established protocols in previous studies investigating cut flower vase life longevity (Jones and Hill, 1993; Clark et al., 2010; Aalifar, 2020). Stems were discarded when 50% of the flower was wilted, petals dropped or had turned brown/discolored and/or neck bending/drooping, drying or general stem decline, and/or mold growth of any kind was observed on the flower (Jones and Hill, 1993; Clark et al., 2010; Aalifar, 2020; Kalinowski et al., 2022).

2.5 Data analysis

Data from the survey were entered into IBM SPSS Statistics (version 30; IBM Corp., Armonk, NY, USA) and analyzed using analysis of variance (ANOVA) tests, post hoc Duncan’s multiple range test, and frequency statistics.

3 Results and Analysis

3.1 Vase life findings for first harvest of Zinnia elegans

ANOVA tests were used to determine if there were differences in vase life between the treatment groups. Significant differences were found in the minimum, maximum, and average vase life within the first harvest. Post hoc tests were used to determine where these differences occurred. Zinnia stems that did not receive a stem cutting and were placed in tap water and stems that did receive a cutting in tap water showed similarities between the test groups, both had a minimum vase life of 8 d (Table 1). Zinnia stems that did not receive a stem cutting and placed in floral food solution and stems that did receive a cutting in floral food solution also showed similarities between the test groups, as they also shared a similar minimum vase life of 12 d and 11 d, respectively (Table 1). There were differences between tap water and floral food solution test groups, as the vase life varies by 3-4 d between the two groups. The zinnias within the flower food solution groups were found to live longer than zinnias in the tap water groups.

Regarding the differences in maximum vase life, it was found zinnia stems that did receive a stem cutting and placed in tap water had a maximum vase life of 15 d, while stems that did receive a cutting and placed in floral food solution had a maximum vase life of 22 d (Table 1). Untrimmed stems in tap water and untrimmed stems placed in floral food showed similarities between the groups, having similar maximum vase lives of 21 d and 20 d, respectively (Table 1).

When analyzing the average number of days flowers remained alive in each treatment group, it was found zinnia stems that did receive a stem cutting and placed in tap water and stems that did receive a cutting and placed in floral food solution were significantly different from all the other groups and each other. The zinnias that were cut and placed in tap water had an average vase life of 11 d, while the zinnias that were cut and placed in a flower food solution had an average of 16.76 d, a difference of 5.76 d.

3.2 Vase life findings for second harvest of Zinnia elegans

ANOVA tests were run on the data to determine any differences between the test groups, looking specifically at vase life. Significant differences were found within the second harvest treatment groups based on their maximum, minimum, and average vase life. Post hoc tests examined where these differences occurred. Test results revealed that the uncut stems in tap water and the cut stems in tap water showed similarities, as the two trials shared a minimum vase life of 7 d. The cut stems in tap water and uncut stems in flower food showed statistical similarities in the study. Uncut stems in a floral food solution and cut stems in floral food solution showed similarities, as they had a minimum vase life of 10 d and 9 d, respectively (Table 2).

ANOVA also indicated differences in the maximum vase life for zinnias in the second harvest based on the treatment groups. Post hoc analysis found the uncut zinnia stems in tap water and cut stems in tap water showed similarities between the test groups. These two trials shared a maximum vase life of 19 d. The cut stems placed in tap water and uncut stems placed in a floral food solution showed similarities in their test groups as well. These two test groups had a difference between the maximum vase life of 2 d. The uncut stems and trimmed stems both placed in the floral food solution showed similarities, as their maximum vase life was both 21 d.

When comparing the average vase life between the four treatment groups, ANOVA showed that uncut and cut stems placed in tap water had similarities between the trials within the second harvest test group, as did uncut and cut stems placed in a floral food solution. While there were differences between tap water and floral food trials, the variation between uncut stems versus cut stems placed in tap water had an average vase life difference of 0.36 d. The difference between the floral food solution groups, both uncut and cut stems, was 2 d. However, the two flower food groups both average higher vase life than the tap water groups by 1.76-4.12 d.

3.3 Vase life findings for combined harvest data of Zinnia elegans

The data from both harvests was combined and analyzed as a whole to determine if there were differences in the treatment groups based on the collective data for all 200 flowers. ANOVA tests were run on the data to determine any differences in vase life among the test groups. Significant differences were found between the maximum, minimum, and average vase life based on the treatment group the flowers were placed. Post hoc tests used to determine where these differences occurred. ANOVA revealed that the uncut stems and the cut stems across all test subjects placed in tap water showed similarities, as well as uncut stems and the cut stems across all test subjects placed in a floral food solution showed similarities. It is important to note that the differences were between the water type, tap water and floral food, rather than between the factor of if the zinnia stem was trimmed or not.  In both tap water groups, the overall minimum day was 7 d, while the floral food solution test group’s minimum days were 10 d for uncut and 9 d for cut stems. This is 2-3 d longer than the minimum for both tap water test groups (Table 3).

When analyzing the maximum vase life, it was found the uncut stems placed in tap water showed similarities between both cut stems in tap water and uncut stems in floral food solution, however, cut stems in tap water and uncut stems in floral food indicated differences from each other. Both uncut stems in tap water and uncut stems in floral food had a maximum vase life of 21 d. The cut stems and uncut stems in tap water were also found to be similar, having a difference of 2 d in maximum vase life. In this trial, the cut stems in the floral food solution were significantly different from all the other test groups, having the longest vase life of 22 d (Table 3).

ANOVA revealed that for average vase life, there were similarities between uncut and cut stems that were placed in tap water. Both the uncut stems and the cut stems that were placed in the floral food solution differed from each other as well as the tap water groups. The average vase life for uncut stems in tap water was 12.8 d and cut stems in tap water was 11.7 d, a difference of 1.1 d. Conversely, the uncut stems in the floral food solution group lived an average of 14.7 d and cut stems in the floral food solution averaged 16.46 d.

3.4 Comparison of vase life between harvest groups

ANOVA tests were used to determine if there were any differences in the vase life of the zinnias between the first and second harvest group. No statistically significant differences were found between the maximum, minimum, or average days of vase life between the first and second harvest groups, indicating that vase life between harvests was relatively the same (Table 4).

4 Discussion

Overall, it was found that the use of flower food extended the vase life of zinnia elegans regardless of if the stems were trimmed or not. Trimming the stems of zinnias that were placed in the floral preservative solution was found to extend the vase life the longest. Past studies have found that floral food prolongs the vase life of various fresh cut flowers (Asrar, 2012; Nguyen and Lim, 2021; Zeng et al., 2023). Findings from this study indicated there were significant differences between zinnias that were trimmed and placed into tap water in the first harvest when compared to all other treatment groups within the first harvest, however this was not consistent with findings from the second harvest or when the flowers from both harvests were looked at collectively. Though it was not found to be significantly different, when the zinnias were looked at collectively, overall, the zinnias that were placed in tap water and had their stems cut had the shortest vase life when compared to all other groups. These findings support past research completed by (Kalinowski et al., 2022) which stated that leaving the stems in tap water untrimmed will slightly lengthen the vase life of Zinnia elegans. This would indicate that should floral food not be available for use, then the proper recommendation for Zinnia elegans is to leave the stems untrimmed in tap water. The shortened vase life that was observed when cutting stems placed in tap water could be a result of a wound-induced xylem occlusion, which occurs in some flowers species due to a stress response when their stems are cut (Manzoor et al., 2024).

No significant differences were found in the vase life of the zinnia between the two separate harvests. Previous research has found that earlier harvests of zinnias had longer vase lives than those bloom that were harvested later in the growing season (Kalinowski et al., 2022). Only two harvests taken two weeks apart were used in this study. Results investigating vase life between harvests from this study could have potentially changed if additional harvests of zinnia been investigated or more time had passed between harvests. Additional harvests over an extended time period should be investigated in similar future research studies.

Retail florists, specialty cut flower farmers, educators, and home gardeners can all benefit from this research. Proper post-harvest techniques are critical to implement immediately upon cutting the blooms from the mother plant. From a cut flower farmer perspective, it is important to properly hydrate the stems and know how to care for the zinnias before sending them out to buyers, markets, or selling them. Farmers may also benefit from sharing the proper care techniques with the buyers to ensure longevity of vase life in the retail setting. Home gardeners and consumers of fresh cut zinnias could potentially benefit the most from this knowledge, as flower preservatives for fresh cut flowers are not commonly purchased by the general population. Publishing updated tips on keeping zinnias looking fresh for the longest amount of time that are written for and accessible to the general public should be considered. Extension services that offer classes on cut flower cultivation and floral design is another way to share the proper post-harvest protocol for zinnia when handling them in the absence of floral preservatives with the public.

5 Conclusions

Findings from this study indicated that the use of floral preservatives in combination with trimming the ends of the stems significantly increases the vase life of zinnia. Additionally, differences were observed in the vase life of zinnias placed in tap water based on whether their stems were trimmed or not, with trimmed stems exhibiting the shortest overall vase life compared to all other treatment groups. These findings suggest that, in situations where floral preservative solutions are unavailable, the recommended postharvest handling practice for Zinnia elegans may be to leave stems untrimmed to maximize vase life. Results may not apply to other flower species, as Zinnia elegans may respond differently to treatments than other cut flowers. Also, the study focused only on postharvest conditions over a limited period and does not account for long-term storage or transportation factors affecting vase life. Based on the findings from this study it is recommended to study other cultivars of zinnias to see if they produce the same results using these treatments as well as other cut flower grown by small regional growers such as cosmos (Cosmos bipinnatus), sunflowers (Helianthus), marigolds (Tagaetes), celosia (Celosia argentea) to investigate if other specialty cut flower species respond in a similar manner.

Authors’ contributions

Lauren Baskin and Cole Etheredge were the principal researchers who conceptualized the research idea, collected, and analyzed the research data, and prepared the manuscript. James DelPrince, Tongyin Li, and Myles Landers assisted in analysis, verification, editing, and proofreading of the manuscript. All authors read and approved the final manuscript.

Conflict of Interest Disclosure

The authors declare that they have no competing interests.

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