Larch is a wood valued for its tough, waterproof and durable qualities; top quality knot-free timber is in great demand for building yachts and other small boats, for exterior cladding of buildings and interior panelling. The timber is resistant to rot when in contact with the ground, and is suitable for use as posts and in fencing. The hybrid Dunkeld Larch is widely grown as a timber crop in northern Europe, valued for its fast growth and disease resistance. Larch has also been used in herbal medicine; see Bach flower remedies for details. In central Europe larch is viewed as one of the best wood materials for the building of residences. Planted on borders with birch, both tree species were used in pagan "sagged" cremations. One "sag" (pronounced song) of wood was required for a cremation stack. Sag is used today as a Polish forestry unit measuring approximately 3 Ã— 1 Ã— 1 m. In Siberia young larch leaves are harvested in spring, preserved by lactobacillus fermentation, and used for salads during winter. Larches are often used in bonsai culture, where their knobby bark, small needles, fresh spring foliage and especially autumn colour are appreciated. European Larch, Japanese Larch and Tamarack Larch are the species most commonly trained as bonsai.