Exotic plants, such as Eragrostis plana in southern Brazil, may cause significant problems in agriculture. This study aimed to elucidate the influence of E. plana rhizosphere soil on wheat germination and initial development. Bioassays with soil sampled from an infested agroecosystem were carried out using wheat as the target species. A factorial design was used, crossing soil from the horizontal and vertical distances from the E. plana tiller base and considering seasons as a blocking factor. The interaction between season and vertical and horizontal soil positions influenced normal wheat seed germination, with the lowest values (69%) observed in the winter bottom and intermediate soil positions. The highest abnormal seedling percentage (17.6%) was recorded in the summer middle vertical soil position. Dormant wheat seeds were higher (7%) in the spring bottom and distal soil positions. The season was the most important factor for germination, but hypocotyl, radicle, and total wheat seedling length also varied according to soil position. Shorter hypocotyls and seedlings were registered in the summer soil surface, while shorter radicles were observed in the proximal horizontal soil position in the same season. This variable response of wheat germination and seedling development to the infested soil demonstrated E. plana seasonality. The influence also varied according to the distance from the plant tiller base. These findings may be used to improve E. plana management in infested fields and to understand the mechanism of action of its allelochemicals in future research.