Body of growing medium (1; 101; 201) for cultivation of a plant (2; wherein the body (1; 101; 201) has a longitudinal axis and an external surface; wherein the external surface is defined by: • an upper surface part; • a lower surface part opposite to the upper surface part; • an outer surface part; and • an inner surface part opposite to the outer surface part; wherein the longitudinal axis extends from the upper surface part to the lower surface part; wherein, viewed in the direction of the longitudinal axis, the inner and outer surface parts each extend, from the upper surface part to the lower surface part and each have two opposing longitudinal sides extending in the direction of the longitudinal axis; wherein, in a first transition zone, one said longitudinal side of the inner surface part is connected to one said longitudinal side of the outer surface part and, in a second transition zone, the other said longitudinal side of the inner surface part is connected to the other said longitudinal side of the outer surface part; wherein the body (1; 101; 201) is transformable from a first shape into a second shape; wherein, viewed in a plane transverse to the longitudinal axis, the outline of the second shape is determined by the outer surface part; wherein, in the first shape, the body (1; 101; 201) is unfolded such that the inner surface part is exposed to the surrounding; wherein, in the second shape, the body (1; 101; 201) is folded up such that the inner surface part is folded up onto itself; wherein the growing medium comprises fibres or particulate material; wherein the fibres or particulate material are bonded and that the body of growing medium is a dimensionally stable body; wherein a transverse axis of the body (1; 101; 201) is defined as: • extending, through the body (1; 101; 201), from the first transition zone to the second transition zone, • having, when the body (1; 101; 201) is in the first shape, an elongated line shaped configuration, and • having, when the body (1; 101; 201) is in the second shape, a ring shaped configuration; and wherein, viewed in the direction of the transverse axis, the inner surface part has a profiled configuration allowing said folding up onto itself; wherein the body (1; 101; 201) has at least one bending zone extending from the upper surface part to the lower surface part, the at least one bending zone being more flexible than the adjacent zones of the body (1; 101; 201) to facilitate folding up of the body (1; 101; 201) from the first shape to the second shape; wherein the profiled configuration is arranged to provide, when the body (1; 101; 201) is in the second shape, a nesting of the inner surface part with itself, and characterized in that said nesting is such that, in the second shape of the body (1; 101; 201), the inner surface part interlocks with itself so that shifting of segments of the inner surface part with respect to each other is prevented. • an upper surface part; • a lower surface part opposite to the upper surface part; • an outer surface part; and • an inner surface part opposite to the outer surface part; • extending, through the body (1; 101; 201), from the first transition zone to the second transition zone, • having, when the body (1; 101; 201) is in the first shape, an elongated line shaped configuration, and • having, when the body (1; 101; 201) is in the second shape, a ring shaped configuration; and