Evaluation of some garden flowers as specialty cut flowers in Eskisehir province-Türkiye

Introduction

Cut flowers are commonly cultivated in various growing media, such as soil or soilless and solid or liquid, within greenhouses equipped with different technologies. Setting up and providing these environments for production is very costly, especially in the start-up phase. The selection of plants that are easy to sow, plant, maintain, and harvest and that can be grown in the open field in environments with suitable ecological conditions reduces costs. Therefore, unlike traditional cut flowers (TFC) such as roses, carnations, and chrysanthemums, which require special environments and cultural treatments during cultivation specialty cut flowers (SCF), which are easy to grow and can be grown in the open field, are preferred by growers (Cavins, 1997). SCF cultivation requires less energy than TCF and is safer for people and the environment. In addition, the SCF group can include annual, biennial, and perennial herbaceous plants, as well as woody and bulbous plants. The wide range of products is an advantage for the sector (Salachna, 2022). The lower production costs of plants meeting these conditions and the greater market interest in new varieties encourage the use of SCF groups as cut flowers (Bachmann, 2006). On the other hand, there are gaps in the sustainability, marketing, and promotion of these groups (Darras, 2021). For a plant to be utilized as a cut flower, factors such as consumer demand, flowering season, growing conditions, stem length, and vase life should be considered (Yue & Hall, 2010; Abdullah, Ahmad & Dole, 2020).

SCF cultivation is widespread in the United States due to the prevalent importation of TCF from producer countries such as Ecuador and Colombia. Therefore, many local cut flower growers have opted to engage in this type of farming to remain competitive (Yue & Hall, 2010). In addition, the production of SCF in Australia prefers native species such as wax flower (Chamelaucium uncinatum), kangaroo paw (Anigozanthos spp.) and thryptomene (Thryptomene spp.), Acacia species native to Australia, such as A. dealbata, A. retinodes, and A. baileyana, which are perennial woody plants, are grown commercially in countries such as Italy and Israel, as well as Australia, because their showy flower clusters are used as cut flowers. In the USA, the market share of Antirrhinum majus, Echinacea purpurea, Helianthus annuus, Limonium sinuatum, Matthiola incana, Scabiosa atropurpurea, Zinnia elegans, and many other SCFs has increased (Darras, 2021).

According to 2022 data from TUIK, Dianthus sp. is the most commonly cultivated cut flower in Türkiye, followed by Rosa sp., Chrysanthemum sp., and Gerbera sp. (TUIK, 2023). One of the primary issues facing Turkish cut floriculture is the restricted range of cut flower products available for sale. This situation exacerbates the country’s reliance on foreign sources for production materials. Since certain species are grown in cut flower production in Türkiye, it remains behind in the world cut flower sector market despite the advantage of climatic conditions. Therefore, there is a need to increase the variety of cut flowers in local production. There are not enough studies and applications on SCF production in Türkiye. Several scientific studies have evaluated the potential for cut flowers in natural vegetation in Türkiye (Turkmenoglu & Fakir, 2016; Ari & Akin, 2010; Yilmaz, 2012; Kebeli, 2021). However, there has been no implementation of SCF production in practice. There has been a dual structure in cut flower production in Türkiye for years. One of them is the enterprise using relatively advanced technology, having large production areas, and producing for export with more professional marketing systems, while the other is the enterprise with insufficient technological equipment, producing in small areas as family businesses, and offering their products to the domestic market to a large extent (Ozturk, Temel & Erken, 2014). SCFs are alternative products, especially for small family businesses producing for the domestic market. SCFs are usually grown in smaller quantities over a shorter growing season and are mostly sold at local farmers’ markets as they are not as transport-resistant as TCFs and can only be stored for limited periods of time (Landford, Curtis & Stock, 2023).

Zinnia belongs to the Compositae family and is native to Mexico and Central America (Riaz et al., 2008). Zinnia elegans, an annual summer flower, is the best known and cultivated species of the genus Zinnia and became popular in Europe in 1790 (Burlec et al., 2019). Zinnia elegans is a short-day plant (Boyle & Stimart, 1983; Park, Kim & Kim, 2013). Tagates erecta is native to Central and South America, especially Mexico, and belongs to the Asteracea family (Singh et al., 2015). Tagates erecta is a commercially known species with a colour range from yellow to orange (Aslam et al., 2016). Helianthus is a plant native to North America that was used by Native Americans as a source of food, dye, and medicine (Short, Etheredge & Waliczek, 2017). Today, Helianthus annuus is commonly used as an ornamental plant (Sloan & Harkness, 2006). Tagates erecta and Helianthus annuus are facultative short-day plants (Boyle & Stimart, 1983). Gomphrena globosa is an annual plant that belongs to the Amaranthaceae family and is native to Central America (Ashwini, Patil & Chethan Kumar, 2019; Yaseen et al., 2022). It is widely used in borders and beds. It is also used as dried flowers (Yaseen et al., 2022). Gomphrena globosa is a neutral day plant (Boyle & Stimart, 1983). The genus Centaurea belongs to the family Asteracea and contains about 400–500 species. Most are native to the eastern Mediterranean and some to Europe (Kadman-Zahavi & Yahel, 1985). Centaurea cyanus, an annual meadow plant with blue-violet flowers, is also known as an ornamental plant (Yang & Zhang, 2022; Kulchenko et al., 2020). Centaurea cyanus is characterised as a long-day plant (Seidlová, 1964). Cleome spinosa is an annual or biennial herbaceous plant of the Capparidaceae family, native to tropical America and now widely cultivated throughout the world (Qin et al., 2012). The species, which is widely used for medicinal purposes, is also used as an ornamental plant (Albarello et al., 2006). Cleome spinosa is a facultative short-day plant (Currey, Lopez & Mattson, 2011).

In this study, it was aimed at increasing the diversity in the market by evaluating the potential of some seasonal flowers to be used as cut flowers and, at the same time, popularizing this cultivation, which is possible to grow on open land and requires less cost. This study is derived from Ilkay Coskun’s master thesis.

Materials and Methods

Results

Phenological results

Seeds of all plants were sown in the first week of May under greenhouse conditions. The plants, which completed seedling development in 3 to 4 weeks, were planted in the open field in the second and third weeks of June. All plants flowered in July and were harvested in the same month. The flower harvest of Cleome spinosa continued until the third week of August and that of Centaurea cyanus until mid-September. Zinnia elegans, Tagates erecta, Helianthus annuus, and Gomphrena globosa were harvested until the last weeks of October (Table 2).

Table 2:

Phenological observation of plant materials.

	May				June				July				August				September				October
Z.e	•		θ	θ	θ	+	⊥	▴
T.e	•		θ	θ	θ	+	⊥	⊥	▴	▴
H.a	•		θ	θ	θ	+	⊥	⊥	⊥	▴	▴
G.g	•		θ	θ	θ	θ	+	⊥	⊥	▴
C.c	•		θ	θ	θ	+	⊥	▴
C.s	•		θ	θ	θ	+	⊥	▴	▴
Description
•	Sowing seeds
θ	Germination
+	Planting seedlings in the field
⊥	Seedling growth
▴	Budding
	Flowering and harvest

DOI: 10.7717/peerj.17114/table-2

Discussion

The suitability of a flower for the cut flower trade depends on some parameters. A straight and strong stem, flower size, vase life, maturity, uniformity, and leaf quality are among the factors that should be used in cut flower classification (Reid, 2004). In addition, post-harvest resistance, easy handling, and, of course, yield are other factors besides visual factors. Varu & Barad (2010) stated that flower size, harvest stage, odor and freshness determine the quality of cut flowers. In the global cut flower trade, it can be said that, in general, optimal stem length and flower size, together with the maximum number of flowers are the determining criteria for a good cut flower (Mladenović et al., 2020). The long flower stem is a reason for preference, as it is easy to harvest. Cut flower industry standards for preferred stem length vary by species and location. For example, the minimum stem length for roses to be exported is 40 cm, while the minimum stem length for roses to be offered on the domestic market is 25 cm. Moreover, it is worth noting that the majority of cut flower distributors favour a stem length of no less than 46 cm, irrespective of the species (Loyola, Dole & Dunning, 2019). Cut flower growers consider the stem length to be marketable when it is between 30 and 41 cm at the minimum (Kelly, 1991). In our study, the minimum stem length (38.3 cm) of Zinnia elegans was recorded in July, the first harvest month. However, the average stem length in July was 48.1 cm. The minimum acceptable stem length for post-harvest evaluation of Zinnia elegans plants is considered to be 30 cm (Martins et al., 2021). In Tagates erecta, the minimum stem length (24.9 cm) was determined in October at the last harvest. The lowest average stem length (29.8 cm) according to months was also in October. Helianthus annuus and Gomphrena globosa had the lowest average stem lengths of 32.2 and 16.2 cm respectively, in October. The minimum average stem length was found in September (18.9 cm), the last harvest time for Centaurea cyanus, and in August (30.3 cm), the last harvest time for Cleome spinosa. From these data, it can be concluded that the minimum stem length values of Zinnia elegans, Tagates erecta, Helianthus annuus, and Cleome spinosa are more suitable for cut flower use, while the stem lengths of Gomphrena globosa decreased in September and October, but stem length averages in July and August were more suitable for cut flowers. In Centaurea cyanus, the maximum length of the stem (31 cm) was measured in July. The average stem length for July was 26.4 cm. Some short-stemmed cut flowers can be used in bridal bouquets or in multiple arrangements. This creates a contrast between the different sizes.

On the other hand, Reid (2004) notes that objective standards such as stem length, which is still the main quality standard for many flowers, may have little relevance to flower quality, vase life, or usefulness.

When selecting species for specialty cut flower production, other important characteristics besides stem length are stem strength, early flowering, disease and pest resistance, heat tolerance, and vase life (Kelly, 1991). Stem thickness is usually a good indicator of the strength of the stem. A long stem with a thin stem diameter is more likely to bend or break than a shorter stem of the same thickness or a stem of the same length with a larger stem diameter (Ortiz, Hyrczyk & Lopez, 2012). Considering the stem thickness of the plants examined in the study, the maximum stem thickness value of Zinnia elegans was 4.4 mm in July, and the highest value (3.7 mm) in terms of mean stem thickness was found again in July. Riaz et al. (2011) reported that the stem thickness of Zinnia plants grown in different environments was 5.3 and 6.8 mm, while Sardoei, Fahraji & Ghasemi (2014) mentioned that the stem thickness values of Zinnia elegans plants grown in different environments were recorded between 2.2 and 3.1 mm. Demirel et al. (2021) stated that the stem thickness of Zinnia elegans plants varied between 5.5–7.3 mm at different irrigation levels. In comparison with other studies, it can be said that the value for the thickness of the stem is low. Halagi et al. (2023) studied the effect of planting distance and pinching on Tagates erecta and found the thickest stem to be 1.64 cm and the thinnest to be 1.48 cm. Meena et al. (2015) obtained a maximum stem thickness of 1.40 cm and a minimum stem thickness of 1.30 cm in Tagates erecta in their study, where they tested planting time, planting distance, and pinching treatments. Priyadarshini, Palai & Nath (2018) examined the effect of nitrogen applications on the development of Tagates erecta and reported that while the stem thickness was 0.89 cm in the control group plants, the maximum stem thickness was 1.37 cm. In the study, the maximum stem thickness of Tagates erecta was 5.1 mm, the maximum average was 4.6 mm in July, and the minimum was 3.2 mm in October. Compared to other studies, the stem thickness value is thought to be thin. There is no scientific study on the stem thickness of Centaurea cyanus.

In the study, the maximum stem thickness value of Gomphrena globosa was 3 mm in July, while the highest monthly average was 2.3 mm in the same month. Green et al. (2010) found the average stem thickness to be 2.1 mm in May and 2.7 mm in August. While the mean value for July was close to that mentioned in the previous sentence, low values for stem thickness were recorded in the other months. The desired stem thickness of Helianthus annuus for general floral arrangements should be 0.5–1.5 cm, according to Sloan & Harkness (2006). In this study, the months of July (7.1 mm) and August (6.3 mm) met this criterion with regard to the values of the stem thickness of Helianthus annuus. However, it remained below this standard in other months as air temperatures began to fall. The stem thickness of Cleome spinosa has not been scientifically studied.

The flower diameter may vary between species and varieties, as it depends on genetic factors. The diameter of the flower is not the most important criterion for determining the quality of a cut flower. As relatively large and colourful flowers attract more attention, they can be used in bouquets in quantities of one or fewer. On the other hand, minimal flowers can be used more intensively to create bouquets or as a complement to other flowers. In this context, among the plants we used in our study, with Helianthus annuus, Cleome spinosa, Zinnia elegans, and Tagates erecta, which have the largest flower diameter, respectively, fewer plants can be used when forming bouquets. Centaurea cyanus and Gomphrena globosa can be used as filler material with their minimal flowers, or bouquets can be created using a larger number of flowers.

Vase life is a critical factor in determining the market value of cut flowers. However, since it takes several days for cut flowers to be sold from farmers to general consumers through retailers, the quality of cut flowers may decrease during this period (Horibe, 2020). The harvest period of the flower is also an important factor in vase life. The optimal harvest time for different species of cut flowers is different. To ensure the longest possible vase life, flowers should be harvested at the proper stage of development (Senapati et al., 2016).

Iqbal et al. (2012) examined the changes in vase life by applying different growth regulators to Zinnia elegans plants after harvest. They recorded the shortest vase life (6.3 days) in the control group without any treatment. The longest vase life was obtained from salicylic acid treatment, with 11.3 days. Ahmad et al. (2012) reported that the average vase life of Zinnia elegans is 13.4 days. In our study, the results of the vase life of the Zinnia elegans (maximum of 13.3 days, maximum monthly average 12.2 days) are satisfactory in comparison with other studies. The average maximum vase life of Tagates erecta was 12.8 days, while the minimum was 11.2 days. According to Ahmad & Dole (2014), in their study, where they applied homemade and commercial flower preservatives to Tagates erecta flowers after harvest, they determined the longest vase life to be 15.7 and 15.5 days after different treatments. The lowest value was found at 7.9 days in tap water. Halagi et al. (2023), the longest vase life was found to be 7.4 days in Tagates erecta with different planting distances and pinching treatments. In this case, the vase life results obtained from flowers kept in tap water without any treatment in our study are satisfactory.

Hanks & Mason (2017) stated that the average vase life of Helianthus annuus is between 7 and 11 days; similarly, Kilic et al. (2020) stated that it is 8.9 days. The results of our study (7.6–9.5 days) are consistent with these studies.

Gomphrena globosa flowers have a vase life of 7.5–10.8 days in our study. Grant (2021) states that Gomphrena globosa has an average vase life of 7 days, and Saghajit (1994) says 11 days. The values obtained in our study were found to be compatible with other studies.

Although there are not many studies on the vase life of Centaurea cyanus, Sellam et al. (2016) reported that the vase life of Centaurea moschata varied between 4.6 days in the control group, 6 days in sucrose treatment, and 9 and 9.6 days in plants in which various bioregulators were used. In our study, the maximum average for Centaurea cyanus was 6.8 days.

Clark et al. (2010) reported that the average vase life of Cleome hassleriana was 5.9 days. The average maximum vase life of Cleome spinosa flowers was 7.3 days in our study. In terms of vase life values, similar results were obtained with the study of Clark et al. (2010).

Nguyen & Lim (2021) state that each type of cut flower has a different vase life and divide the vase life into three groups: short (less than 5 days), medium (6 ~ 14 days), and long (2 ~ 4 weeks). In this respect, it can be said that all flower species evaluated in the study have medium vase life values, except for the flowers of Centaurea cyanus (5 days) harvested in July.

The ranking in terms of flower yield values per plant during the production season is as follows: Helianthus annuus (11 total flowers per plant), Gomphrena globosa (seven total flowers per plant), Zinnia elegans (four total flowers per plant), Centaurea cyanus (four total flowers per plant), Tagates erecta (four total flowers per plant), and Cleome spinosa (one total flower per plant). In our study, no cultural treatments such as pinching and different planting spacing were applied to increase yield. However, it has been reported that widening the planting spacing (Armitage, 1987) and pinching increase flower yield (Wien, 2016; Ehsanullah et al., 2021) and delay flowering (Cheema, 2018) in some annual ornamentals. For example, Wien (2016) reported that widening planting spacing and pinching positively affected yield in Helianthus annuus; Ullah et al. (2019) reported that especially double pinching improved many parameters related to yield and plant quality in Zinnia elegans; Singh, Singh & Ahirwar (2018) reported that wide plant spacing (60 cm × 60 cm) increased flower yield per plant in Tagates erecta. Similarly, Nathan et al. (2019) reported that pinching 15 days after planting and foliar application of bioregulator increased flowering and improved flower quality in Gomphrena globosa, while Selahvarzi et al. (2023) reported that pinching in Helianthus annuus prolonged the flowering period by about 1 week.

Phenologically, the flowering period is longer in Zinnia elegans (16 weeks) and Tagates erecta (14 weeks), followed by Gomphrena globosa (12 weeks), Helianthus annuus and Centaurea cyanus (11 weeks), and Cleome spinosa (6 weeks). The first flowering was observed in Zinnia elegans and Centaurea cyanus in the first week of June, followed by Cleome spinosa, Tagates erecta, and Gomphrena globosa in the same month, and Helianthus annuus at the end of June. Flowering is influenced by many factors, including the intrinsic characteristics of the plant genotype, the growing medium, and growing conditions (Proietti et al., 2022). In order to regulate flowering in open field cultivation, some practices, such as including many species in the programme during the growing season, planting in rotation, different planting times to bring flowering earlier or later, pinching, and chilling, can be done. It may also be necessary to create low tunnels to extend the growing season.

Grown in the open, these plants require no additional inputs other than fertiliser and weed control during the pre-planting and growing phases, making them more economical than traditional cut flower production (Bachmann, 2006). As they are easy to harvest, no special equipment is required. The fact that it can easily be done on suitable land with the supply of seeds and/or seedlings makes specialty cut flower production economical. As they are sold directly from the farm and/or florists, post-harvest handling such as transport and storage are also economical (Landford, Curtis & Stock, 2023). Cut flower cultivation in Türkiye is mainly concentrated in the Aegean and Mediterranean regions due to the climatic advantage of having a Mediterranean climate type (Baris & Uslu, 2009; Kenanoğlu, 2023). However, the fact that this cultivation can be carried out in the open field, enabling cultivation in the spring and summer months, makes this cultivation possible in other regions of the country. These flowers are more economical than other imported products, especially as they are offered to the domestic market. They also increase product diversity. Considering these aspects, the economic contribution of specialty cut flower cultivation cannot be ignored.

Conclusions

Due to climate change and the environmental, energy, and economic problems it causes, the ornamental horticulture sector, like all other sectors, needs a transformation that adopts an ecological approach. In this context, the cultivation of specialty cut flowers, which can be easily grown outdoors without the need for additional equipment, will be more ecological and economical, especially by supporting the cultivation of natural flowers. In the local market, florists are able to deliver faster and fresher flowers directly from the grower, and offer more vibrant and healthier flowers to the market. It can also offer different alternatives to consumers who are bored with classic-cut flowers and want to see different and more economical flowers. On the other hand, it is possible to carry out the production by selecting the plants that are suitable for the ecology outside the regions with a favourable climate.

The study was carried out in a region with climatic disadvantages in terms of ornamental plant cultivation and where ornamental plant cultivation is not common. The plants have been grown in the open air during the summer period. When we look at both the phenological and morphological characteristics of the flowers, it is possible to say that the development of Zinnia elegans, Helianthus annuus, Tagates erecta, Gomphrena globosa, and Centaurea cyanus plants is good in the Eskisehir region from spring to mid-autumn. In terms of flowering period, it was concluded that the harvest period of all flowers except the Cleome spinosa flower was long. In our study, it was thought that these plants, which are cultivated in order to increase the diversity of production and support local product diversity, should be brought to the cut flower market. In addition, cultivation can be supported in regions where ornamental plants are not cultivated at a low cost. It is very important that this cultivation be carried out with the right plant selection in geographies with climatic disadvantages. Therefore, the plants we evaluated in this study can be a guide for those who want to grow cut flowers in ecologies similar to Eskisehir. To extend the production season, plastic tunnels, which are more economical than greenhouses, can be used as an alternative to open-field production.

Besides, there is a need for more research on the introduction of specialty cut flowers to the ornamental plants sector throughout the country, popularisation of their cultivation and flower quality, flower yield, vase life, storage, and transport of flowers.

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