The calendar of Spiraea flowering in the Mari El Republic

Mukhametova Svetlana Valeryevna ORCID: 0000-0001-7892-6450 PhD in Agriculture Associate Professor; Department of Landscape Gardening, Botany and Dendrology; Volga State University of Technology 424000, Russia, Republic of Mari El, Yoshkar-Ola, Lenin Square, 3, room 245 MuhametovaSV@volgatech.net Other publications by this author

Rusyaeva Dar'ya Mihailovna Graduate student; Department of Landscape Engineering, Botany and Dendrology; Volga State University of Technology landscape designer; IP Green Friend 424000, Russia, Republic of Mari El, Yoshkar-Ola, Lenin Square, 3, room 245 daria.r.0303@mail.ru

Spiraea (Spiraea L.) are deciduous shrubs from the Rosaceae family (Rosaceae Juss.). The genus contains about 90 species, slightly more than half of them have been introduced into culture ^[1]. Species of this genus grow in the temperate climate of the Northern Hemisphere, the greatest diversity is represented in East Asia, mainly in China, where there are about 70 species (47 endemic). Some species can be naturalized and are recognized as invasive in some countries, which indicates their high plasticity to environmental conditions ^[2].

Spirea is highly appreciated in landscaping not only for its unpretentiousness, but also due to its excellent decorative qualities, excellent subtle aroma ^[1]. They reach a height of 15 cm to 2.5 m, the shoots are erect, spreading or creeping. The leaves are alternate, petiolate, simple, from narrowly lanceolate-linear to round, whole, 3-5-lobed, simply or bicolored. Inflorescences are umbrellas, corymbose brushes, simple or complex corymbs, panicles. Flowers with 5 petals, white, light or dark pink, red to purple in color. The fruits are multi–seeded leaflets; the seeds are small, flat, lanceolate ^[3]. There are 3 sections within the genus: Chamaedryon, Calospira and Spiraria. Species from the Chamaedryon section form buds on shoots of the previous year, Spiraria sections on shoots of the current year, Calospira sections on both types of shoots. The type of shoot on which flower buds are formed largely determines the differences in the timing of their blooming ^[4].

According to the timing of flowering, there are 2 groups among the spiracles: spring and summer flowering species. In the first group, the inflorescences are located on the shoots of the previous year, flowering begins in May and lasts until July, it is very abundant, but short (15-25 days). As a rule, the flowers are white in color. These species are characterized by a height of 1-2 meters, strong tillering, durability and, with proper care, can grow up to 50 years. For rejuvenation, the bush is pruned, forming a new one from young shoots. This group includes such species as S. seraya, S. Wangutta, S. sharp-toothed, S. dubrovkolistnaya, S. sinuous, etc. ^[1]. As a rule, higher air temperatures contribute to an earlier start of flowering. In spring, the influence of weather conditions on the beginning of flowering is more pronounced, since the difference between air and water temperatures creates faster convection than in other seasons ^[5]. In summer-flowering species, flower buds are laid at the ends of the shoots of the current year. Flowering lasts from mid–summer to late autumn (June - September), the flowers can be in various shades of pink, red, crimson or bicolor. The height of the plants is from 0.3 to 1.5 m. Spirea of this group must be pruned in spring, shortening the shoots by 10-15 cm, which contributes to the formation of a compact, dense spherical shape and abundant flowering. Summer-flowering spiraea are less durable, they are replaced at landscaping sites after 15-20 years. This group includes S. berezolistnaya, S. belaya, S. belotsvetkovaya, S. trehlopastnaya, S. Bumalda, S. Japonica, etc. ^[1].

Spiraea are widely used for landscaping settlements, in parks and squares, because they withstand the gas pollution of city streets ^[6]. Good care, timely fertilizing and watering, and spraying with water in dry summers contribute to the preservation of the decorative properties of plants. However, spirea is very rarely damaged and practically does not lose its decorative effect. When composing compositions, you can take into account the diverse shape of the inflorescences, the size and shape of the bush. So, in single plantings or hedges, the tallest plant species can be used, for example, S. belaya, S. ivolistnaya, S. Douglas. To create low curbs, as well as for planting on a slide and in rockeries, such species as S. belotsvetkovaya, S. Bumalda, S. Japonica are well suited. Many tall and not very tall plants can frame a single tree or small groups of trees ^[7]. In general, spirea is recognized as one of the best flowering shrubs for creating hedges ^[8]. They can also be used in soil and water protection plantings, as well as in landscaping rocky areas due to their strong root system and resistance to drought and poor soils ^[9]. In addition to being used in landscaping, members of the genus are widely used in traditional and folk medicine. Phenolic compounds, terpenoids, alkaloids, steroids and other compounds have been isolated in plants, among which many exhibit biological activity. Thus, Spiraea species have high potential as a valuable resource ^[10].

Botanical gardens are valued for their extensive collections, which allow for a comparative study of species and varietal diversity in a particular region. In the Botanical Garden-Institute of the Volga State University of Technology (Yoshkar-Ola, Republic of Mari El), spiraea grow in the exhibition "Fruticetum", where a collection of ornamental shrubs is presented according to the conditionally systematic principle of placement. The plants are located on rectangular and square areas measuring 1.5×1.8 m, 3×4 m, 3×3 m, etc. ^[11].

The purpose of the study is to determine the timing of flowering of representatives of the genus Spiraea in the BSI PGTU. The observations were carried out from May to August 2023 with a frequency of 1-2 times a week. The opening of the first flowers was taken as the beginning of flowering, and the mass wilting of the corollas was taken as the end. Based on the xsr criterion. ± σ the distribution of species and varieties into groups with early, medium and late phenophase has been carried out.

The data obtained are presented in the form of a flowering calendar.

Table – Calendar of spiraea blooms in 2023

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It has been established that in 2023, the flowering of spiracles began on May 6. The very first to bloom were S. dubravkolistnaya, S. St. John's wort and S. gray 'Grefsheim'. Also, the group with an early onset of flowering included S. srednaya, S. ostrozubchataya and its variety 'Compacta', which bloomed on May 10-13, S. sinuous (May 15), S. berezolistnaya, S. Billard, S. Wangutta, S. long-chain, S. three-lobed (May 20), S. gorodchataya (May 22). The late onset of flowering was recorded in S. belotsvetkova, S. Douglas, S. Margarita, S. Menzies, S. Sansusiyskaya, S. Fonteneyskaya, varieties of S. Japanese 'Magic Carpet' and 'Ronnenberg', (July 1), S. white, S. charming, S. Japanese 'Crispa' and 'Schirobana' (July 8), S. felt and S. Japanese 'Macrophylla' (July 15). The remaining 29 spiracles are assigned to the group with average flowering dates (May 27 – June 24).

The earliest end of flowering was noted on May 20 in S. dubravkolistnaya, S. gray 'Grefsheim' and S. St. John's wort, also the group with the early end of flowering included S. sharp-toothed and its variety 'Compacta', S. sinuous, S. srednaya (May 27), S. Wangutta, S. gorodchataya, S. three-lobed (June 3), S. long-chain, S. Nipponskaya various. tozenskaya, S. nipponskaya 'Snowmound' (June 10). At a late date, on August 5, the flowering of S. feltnaya, S. ivolistnaya and its variety 'Alba', S. krasnovataya, S. broadleaf finished. The remaining 38 species and varieties of spirea are assigned to the group with average flowering dates (June 17 – July 29).

The shortest flowering period of 12 days was characterized by S. gorodchataya and S. meandering. In addition, the short duration of this phenophase (14 days) has been established in S. Wangutta, S. dubravkolistnaya, S. St. John's wort, S. Nipponskaya various. Tosenskaya, S. Nipponskaya 'Snowmound', S. sharp-toothed and its varieties 'Compacta', S. gray 'Grefsheim', S. medium, S. three-bladed, S. Japanese 'Macrophylla' and 'Magic Carpet'. The longest flowering period is 56 days. It is noted in the scutellum. The group with a long duration of flowering included S. krasnovataya, S. broadleaf (49 days), S. Bumalda, S. ivolistnaya and its variety 'Alba', S. low (42 days), S. Bumalda 'Antony Waterer', S. Lemoine, S. sirenetsvetnaya, S. Rostgorna (35 days). The remaining 31 species and cultivars of spirea are assigned to the group with an average flowering duration (15-28 days).

In the period up to mid–June, mainly spirea with white flowers bloomed, and only 2 species with pink ones - S. Billarda and S. gustotsvetkovaya. Starting from the second half of June, the flowering of spiracles with pink color of flowers prevailed compared to white (28 and 9 names, respectively). In general, the flowering period of the spiracles was 3 months – from May 6 to August 5. Since the timing of phenological development is closely related to the weather conditions of the growing season, it is necessary to further study the timing of flowering of spirea, identify the characteristics of individual species and compile a flowering calendar based on long-term data.

In general, the data obtained are consistent with the data of other authors from different regions ^{[3, 6, 12, 13, 14, 15, 16, 17]} and they are valuable for specialists in the field of landscape architecture and landscaping.

It is known that the expansion of the range of introducents for landscaping is relevant, since their use provides a significant increase in the aesthetic and sanitary properties of landscaping plantings ^[14]. A limited number of spirea species are used in the plantations of settlements of the Republic of Mari El, and thanks to the extensive collection of BSI PGTU, it is possible to enrich the range of spirea in urban plantings, taking into account not only the flowering time, but also the habitus of plants.