Fuente: WIPO "tomato" The present invention relates to a plant growth medium comprising plant fibers which have been modified to reduce and/or cover the lignin at the surface of the plant fiber such as to reduce contact between the lignin and plant roots during their growth in the plant growth medium, to a plant growth medium comprising plant fibers and at least one cellulose product and to a block formed plant growth medium comprising the plant growth medium and a biodegradable binder Further the invention relates to processes for the manufacture of the plant growth medium and the block formed plant growth medium, and to the use thereof for growing plants, e.g. in horticulture and agriculture.