Pollenbloei

Pollenbloei is the period during which pollen is produced and released by the flowers of many plant species, especially wind-pollinated trees and grasses. It marks a key phase in the flowering cycle and varies with latitude, altitude, climate, and yearly weather conditions. During pollenbloei, the male reproductive units, pollen grains, mature in the anthers and are shed into the air or onto pollinators as part of the plant’s reproductive strategy.

The process involves dehiscence of the anthers and the dispersal of pollen grains, which can be transported by wind, insects, or other vectors. Wind-pollinated plants tend to release large quantities of pollen and can produce widespread airborne pollen. Insect-pollinated species may release pollen in smaller amounts and rely more on pollinators. The timing of pollenbloei is influenced by temperature, day length, rainfall, and other climatic factors, and may shift with climate change, often extending the pollen season in many regions.

Ecologically, pollenbloei is central to plant reproduction and genetic diversity. For humans, the period is notable because many people's allergies are triggered by airborne pollen, particularly from birch, alder, hazel, oak, grasses, and other common upstream pollen producers. Monitoring networks track pollen counts to inform health advisories and agricultural planning.

In practice, pollenbloei is studied in phenology and aerobiology through pollen calendars and air-sampling data, helping to forecast pollen levels and understand seasonal patterns across species and regions.