Long-term changes in the optimum planting date of gladiolus in southern Brazil

Abstract

The objective of this work was to test long-term trends in the planting date of gladiolus to ensure marketing of these flowers on Mother’s Day and All Souls’ Day in Santa Maria (latitude: 29° 43’ S, longitude: 53° 43’ W, and altitude: 95 m), Rio Grande do Sul State, Brazil. Minimum and maximum air temperature data from 106 years were used (1912-2017) to simulate the optimum planting date indicated through the PhenoGlad model, aiming to harvest floral stems for both market dates for early, intermediate I, intermediate II and late cultivars. The homogeneity of the historical series was tested using the run test, and the historical trend was tested by the Mann-Kendal test. The magnitude of the trend was estimated with simple linear regression, and the descriptive statistics were calculated. For marketing on Mother’s Day, there was no historical trend that implied a change in the planting date of gladiolus for any of the development cycles. For marketing on All Souls’ Day, there was a positive historical trend only for the early and intermediate cycles I and II; thus, the increase in air temperature implied a delay of 9.2 days, 9.5 days and 6.9 days for the planting date, respectively, indicating that a shortening of the gladiolus development cycle occurred, mainly in late winter/early spring.

Validation of the PhenoGlad model and determination of planting dates of the gladiolo for the state of Paraná

“…is considered a species of great commercial importance, propagated through corms, and cultivated as a cut flower with a great diversity of colors (Schwab et al, 2015;Uhlmann, 2018). In Brazil, the main sales peak occurs on all Souls' days (November 2) (Tomiozzo et al, 2021).…”

“…The cultivars found in the market are hybrids (Tomiozzo et al, 2021) and are distinguished by the color of the florets and the duration of the cycle. The gladiolus crop development cycle is divided into three phases: bulb sprouting, vegetative, and reproductive (Schwab et al, 2015) and these are the environmental conditions that interfere with the growth, development, and quality of the stems.…”