A plant growing block 1 consists of bound mineral wool and comprises a number of coherent plant growth bodies (2) mutually separated by means of two mutually perpendicular sets of parallel grooves (4, 5), the depth of which corresponds to the major part of the height of the growing plant means. The fibres of the block are arranged substantially to lie in planes perpendicular to the surface of the block, eg plane 3. The roots of plants will spread more readily within planes parallel to plane 3 than perpendicular to such planes and as a result the grooves 5 need not be as wide as the grooves 4 and the rigidity of the block is increased.
