Northern white cedar or arborvitae (Thuja occidentalis) is a conifer used above all for dense hedges, thanks to its compact growth and tolerance of clipping. Popular varieties are the narrow, slow-growing 'Smaragd', which needs little trimming, and the faster 'Brabant'. It grows in sun or partial shade in moist, humus-rich soil (pH 5.5–7.0) and adapts to most sites except dry, sandy ground and waterlogged clay. Plant in April or September–October, 50–80 cm apart depending on the variety, and water thoroughly and regularly for the first two years. Trim once or twice a year, in late May or June and again in August, but never cut back into old brown wood – thuja does not resprout from it and gaps remain. Browning usually signals drought or winter desiccation, so water deeply before the ground freezes. Tie columnar plants loosely before winter so heavy snow does not splay them apart. All parts of the plant are poisonous if eaten.