Pollen grains emitted from vegetation can release subpollen particles (SPPs) that contribute to the fine frac tion of atmospheric aerosols and may act as cloud con densation nuclei (CCN), ice nuclei (IN), or aeroallergens. Here, we investigate and characterize the hygroscopic growth and CCN activation of birch, pine, and rapeseed SPPs. A high-humidity tandem differential mobility analyzer (HHT DMA) was used to measure particle restructuring and wa ter uptake over a wide range of relative humidity (RH) from 2 % to 99.5 %, and a continuous flow CCN counter was used for size-resolved measurements of CCN activa tion at supersaturations (S) in the range of 0.2 % to 1.2 %. For both subsaturated and supersaturated conditions, effective hygroscopicity parameters, κ, were obtained by Köh ler model calculations. Gravimetric and chemical analyses, electron microscopy, and dynamic light scattering measure ments were performed to characterize further properties of SPPs from aqueous pollen extracts such as chemical com position (starch, proteins, DNA, and inorganic ions) and the hydrodynamic size distribution of water-insoluble material. All investigated SPP samples exhibited a sharp increase of water uptake and κ above ∼ 95 % RH, suggesting a liquid liquid phase separation (LLPS). The HHTDMA measure ments at RH > 95 % enable closure between the CCN activation at water vapor supersaturation and hygroscopic growth at subsaturated conditions, which is often not achieved when hygroscopicity tandem differential mobility analyzer (HT DMA) measurements are performed at lower RH where the water uptake and effective hygroscopicity may be limited by the effects of LLPS. Such effects may be important not only for closure between hygroscopic growth and CCN activation but also for the chemical reactivity, allergenic potential, and related health effects of SPPs.