Comparative study on the growth and development of annual and biannual plants of species from genus Catalpa at the conditions of Sofia field

Абстракт

The possibility for propagation, ecological requirements and growth peculiarities of the species from genus Catalpa (fam. Bignoniaceae) in Bulgaria are insufficiently studied. Catalpa is a tree with attractive ornamental value, compact form and relatively fixed size. It originates from South America and China. Catalpa spp. Differ significantly from each other by their requirements to environmental conditions (temperature, humidity and others), growth characteristics and susceptibility to diseases and pests. In our country catalpa species and varieties with delayed growth in the time are only few. The objective of this study was to optimize the production of propagating material of catalpa species and their varieties under the conditions of Sofia field. For three years (2014 to 2016), seeds were harvested from the studied species, they were sown, and the young plants were grown for at least 2 years in order to establish their growth abilities and their performance in the ecological conditions in Sofia region. The results of our study showed that direct outdoor sowing reduces the labour costs associated with the production of young plants, but at the expense of the number of plants obtained from the seeds. Laboratory seed germination varied slightly over the years, with an average for the study duration as follows: C. bignonioides – 88.67%; C. x erubescens – 85.66%; C. ovata – 87% and C. speciosa – 91,33%, and at least in one of the years, the seeds of each species had laboratory germination equal to or greater than 90%. The germination of seeds sown in boxes in a greenhouse was on average: C. bignonioides – 79.66%; C. x erubescens – 77.66%; C. ovata – 74,33% and C. speciosa – 85,33%; and under field conditions: C. bignonioides – 28%; C. x erubescens – 20.33%; C. ovata – 17.33% and C. speciosa – 31.66%. At the direct sowing in the first year the plants of C. speciosa reached the biggest height of 101.87 cm and a diameter of 21.3 mm. In the second year, the biggest height was measured for C. ovata – on average 208.33 cm, and the largest diameter for C. speciosa – 32.6 mm.