Summer‐flowering trees and shrubs in landscaping for the south‐eastern coast of the Crimea

Aim. To study the species composition, form diversity, bioecological features of summer‐ flowering trees and shrubs in green spaces of the south‐eastern coast of the Crimea and suggest ways to expand the range. Materials and Methods. The green spaces of Feodosia, Sudak and the localities of Semidvorye, Solnechnogorskoye, Malorechenskoye, Rybachye, Morskoye, Novy Svet, Solnechnaya Dolina, Shchebetovka, Kurortnoye, Koktebel and Primorskiy were investigated. Bioecological and phenological studies of ornamental trees and shrubs were undertaken according to generally accepted methods. Results. The species composition and shape diversity of summer‐flowering trees and shrubs in green plantings of Crimea’s south‐eastern coast were identified. It was found that summer‐ flowering plants make up almost half of the species composition (48.6%) used in landscaping. However, only 23 species are widespread throughout the region, such as Ailanthus altissima (Mill.) Swingle, Albizia julibrissin Durazz., Buddleja davidii Franch., Campsis radicans (L.) Seem., Elaeagnus angustifolia L. etc. The greatest number of species and forms of arboreal plants bloom in early summer, their number decreasing significantly from the second decade of June. Conclusion. An assortment is proposed for increasing the number of trees and shrubs which flower during the summer, taking into account both their decorative visual appeal and their environmental requirements, especially drought and frost resistance. Of great interest are species that bloom from June onwards, especially those which are highly decorative and have a long flowering period, such as Albizia julibrissin, Buddleja davidi and forms, Hydrangea arborescens L., Campsis radicans, Kerria japonica f. plena C.K. Schneid, Robinia viscosа Vent., Vitex angus‐castus L.

Critical role of air and soil temperature in the development of primary and secondary physical dormancy in Albizia julibrissin (Fabaceae)

Physical dormancy (PY) is typically induced by seed coat impermeability that develops once the moisture content of seeds drops below a species-specific threshold. Considering this, we utilized Albizia julibrissin (Fabaceae) to ask (i) whether seeds that mature on the outer branches of trees (directly exposed to sunlight) are more likely to be impermeable than seeds matured under canopy cover; (ii) whether this difference might be explained by the maternal environment in which the seeds mature; and (iii) which conditions impose secondary dormancy following dispersal? Temperature was tracked in both shaded and sun-exposed seed pods throughout the growing season using data-loggers. Temperatures remained lower in pods under canopy cover than those exposed to direct sunlight. Consequently, the moisture content of seeds collected from sun-exposed branches were significantly lower than seeds matured under canopy cover, thereby producing a higher percentage of impermeable seeds. A dispersal-mimicking experiment revealed that seeds matured in sun-exposed branches and subsequently dispersed to an open site for 4 months were more likely to develop impermeability (i.e. secondary dormancy). The opposite was found to be true for seeds matured in shaded branches and subsequently dispersed to a canopy-covered site. We conclude that the microclimate of both the maternal environment in which seeds mature, and the site to which they disperse, determines the development of primary and secondary dormancy, respectively.