Journal of Apicultural Science

Blooming and pollen production of several representatives of the genus Centaurea L.

Journal of Apicultural Science. Volume 50, Issue 2, Pages 13-20, ISSN (Print) 1643-4439
Investigations on the flowering time and pollen efficiency of three Centaurea species were conducted in the years 2002 - 2004. The study included Centaurea cyanus L. - cornflower and C. scabiosa L. - greater knapweed which grew in the districts of Sławin and Czechów of the city of Lublin, and C. stoebe L. (=C. rhenana) which occurred at Pliszczyn near Lublin. The flowering of the Centaurea species in anthropogenic communities lasted, under Poland's conditions, continuously from mid-June to the first decade of September. The development of all disc florets in the capitulum lasted for ca. 2 days (C. cyanus), 4 - 5 days (C. stoebe), 5 - 8 days (C. scabiosa). C. scabiosa and C. stoebe form a similar number of pollen-yielding disc flowers per 1 m2, averaging 95,000. In the case of C. cyanus only 5,800 flowers per 1 m2 were found. The mass of pollen delivered was found to be species-related as dependent on anther size and productivity of the archesporial tissue. Dry matter weight of pollen per 100 stamen heads averaged from 3.93 mg to 6.12 mg. Pollen efficiency of C. scabiosa averages 283.3 kg per 1 ha, varying from year to year from 225 to 390 kg. C. stoebe may yield 173 - 213 kg of pollen per 1 ha, C. cyanus yielding only 14.3 kg per 1 ha. The species were visited in high numbers by Apis mellifera which accounted for 60 - 80% of all pollinators.
Centaurea sp, blooming biology, pollen efficiency, pollinators
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