A method of controlling the integrity of a fiber material plant propagation cell (1.1, 1.2), wherein a plant propagation cell material (2) is formed of natural fiber and biodegradable polymer fiber, a plant propagation cell is formed from said cell material, a plant (P) and plant substrate (S) is introduced into the plant propagation cell and the plant propagation cell is positioned and supported in a cell carrier (20) during propagation whereby a degradation triggering fluid is applied to the plant propagation cell material prior to a planting of the plant propagation cell.