The expanded polystyrene container for the culture of plants, comprises a cell intended to conform a block of the plant culture, and a block having truncated cells (4) present between upper and lower sides (2, 3) of the container. A wall of the cell is covered by a layer or a deposit of self-undercutting toxic product to stop a longitudinal growth of certain roots of the plants to be cultivated when the end of the plant approaches or attains the toxic product. The toxic product is based on air extinguisher, Bordeaux mixture and/or fungistatic-fungicide. Independent claims are included for: (1) a process for the preparation of a container and (2) a process for the preparation of a block for plant culture.
