Fuente: WIPO "tomato" The invention regards a growth substrate unit comprising mineral wool, the unit having a planar top surface comprising one or more seed hole openings, each seed hole defining a closed channel extending substantially perpendicular to the planar top surface, wherein each closed channel comprises a closed end section with a constant 5 cross-sectional area where the maximum dimension of the cross-sectional area is 5 to 25 mm, and wherein the closed channel has a depth of 35 to 60 mm.