The survey was carried out on the seed bank of several patches of an open, semiarid sandy grassland (Festucetum vaginatae Rapaics ex Soó 1929 (Borhidi 1996)). We chose four, approximately 20 m × 20 m large, adjacent patches, different in their species composition and total cover. Soil samples were taken in early spring and at the end of summer, in two consecutive years. We determined the seed bank of the samples with the seedling emergence method. The fact that we found the seeds of only two species that were not present in the vegetation indicates the isolated and without artificial disturbed state of the grassland. The vegetation and the seed bank of the patches showed a low degree of similarity in the same period, while the composition of the spring aspect reflected clearly in the seed bank of late summer in all four patches. Results showed that mosaic-like appearance is not only characteristic of the vegetation, but also the seed bank of the soil. Differentiation of the seed bank manifested mostly after the period of seed-fall, at the end of summer, while in early spring it was less expressed. On the basis of the differentiation of the seed bank we can conclude that not the dispersion of seeds, but natural vicinity of mother plants was decisive in forming the spatial variation of the seed bank.