At germination, seedlings may be encouraged by the surrounding vegetation. This facilitation was studied in dandelions in a manipulative experiment to determine whether a nurse plant, either maple trees or alfalfa, assisted in the germination of dandelion seeds and whether there was a difference in germination when additional moisture (irrigation) was provided on top of rainfall. Seeds were sown into 33-cm² “arenas” and surrounded by plastic collars, which prevented the seed from being eaten by predators. Germination was recorded at 1- to 2-d intervals, and the percentage of the seeds that germinated and their time to 50% germination (T₅₀) was calculated. The nurse plant was consistently associated with seed germination. Compared with bare ground, the germination percentage was lower under tree cover, whereas T₅₀ was shorter under the cover of herbaceous plants (alfalfa). The values for the germination percentage and T₅₀ were similar under tree and herb nurse plants when the soil was irrigated. Nurse plants facilitated germination via their effects on understory humidity. Facilitating the germination of dandelions through the presence of nurse plants contributes to their propagation in crops.

Nomenclature: Dandelion, Taraxacum officinale G.H. Weber ex Wiggers TAROF; alfalfa Medicago sativa L.; Norway maple, Acer platanoides L.