Thuja occidentalis, or northern white cedar, is an evergreen tree in the cypress family. It grows to 40 feet tall in a typical conical shape. Thuja occidentalis can live for a very long time; according to the U.S. Department of Agriculture, a Thuja occidentalis in Ontario is more than 1,650 years old. These trees are native to North America and are a favourite food of deer. Thuja occidentalis is also a favourite tree for bonsai enthusiasts, who grow it in a miniature version. Thuja occidentalis prefers cooler climates, and does best planted in climate zones 2 through 7.
Plant the Thuja occidentalis in a sunny location with moist, rich soil. It can survive being planted in a shady area, but its branches and canopy will be sparse. Thuja occidentalis can handle both seasonal flooding and drought conditions.
Water the newly planted Thuja occidentalis regularly until it has become established. After that time, it should not need watering, except in unusual circumstances. Thuja occidentalis can survive drought conditions, but if the drought is severe or long-lasting, it will benefit from watering at that time.
Most Thuja occidentalis do not require fertiliser, but you can fertilise it with a high-nitrogen fertiliser to promote a deep green colour to the foliage. Fertilise once with a slow-release fertiliser in the spring.
Prune the Thuja occidentalis occasionally to help it maintain strength and vigour. Prune any additional leaders that develop, as the tree grows strongest from a single leader. Be careful and do not over-prune; it does not recover well from aggressive pruning. Thuja occidentalis is commonly pruned to a hedge shape or as a screen; this type of pruning should be started early with young trees.
Tie the branches of the Thuja occidentalis to protect them during heavy snows. The smaller, upper branches can break under heavy snowfall loads. The Thuja occidentalis' upper branches are sometimes pulled down and tied in close to the boot to protect them, but this can kill the inner branches that are covered. The recommended practice to tie the branches in a support fashion, with a loop around the branch tied up to the main trunk. This method keeps the branches from being weighted down while allowing the lower and inner branches to receive sunlight.