The present invention relates to a plant protection device comprising a tubular sheath formed with a wall of decomposable material and extending longitudinally from an open insert end (4) to an open top end (5), the sheath wall defining a tubular section (r1； r2) the size of which allows the sheath to be applied over a seedling while enclosing the seedling from its root end to below its top end. In applied position about the seedling, the sheath provides by its wall, at least over a portion of the sheath length, an engagement with the green part of the seedling, i.e. stem, branches and needles, caused by a gripping force that gradually ceases in advance of disintegration of the sheath wall in its entirety.
