STUDY ON THE MORPHOLOGY AND FLOWERING OF COMMON RAGWEED IN CLIMATIC ZONE OF BIHOR COUNTY

For the development of ragweed control strategies, it is necessary to know its morphology and flowering. In the suburban area studied most ragweed bushes reach a height of up to 1.50 m and ramifications up to third order. Therefore, plant sizes reflect a medium growth. The number and maximum lengths to which male inflorescences reach in August reveal the huge amount of pollen that unmowed ragweed populations can provide. The dimorphism for feminine inflorescences is observed. Most plants have only sessile groups. If they have both types of inflorescences, the number of sessile groups is higher than the pedunculated ones. Due to climatic changes feminine flowers appear two weeks later than two decades ago. These appear in mid-August at the level of the last two ramifications. In order to prevent maximum flowering - for significantly reduce the amount of pollen in the air and the amount of seeds -ragweed must be mowed twice in the climatic zone of Bihor County. For start in the last days of July or the first days of August. To further reduce seeds production should also be mowed in the first half of September.