The evergreen thuja (Thuja occidentalis) are also known as “trees of life”. They belong to the cypress family and are mostly used as topiary hedges.
Now, before you prune your hedge, here’s what you should keep in mind: Thuces are quite tolerant of pruning, but this only applies to the young herbaceous shoots. These conifers do not tolerate pruning into the old wood. Old branches can no longer rejuvenate, the interfaces remain bare after a radical intervention in the hedge.
Cutting back the thuja hedges is possible from winter to late summer. It is best to cut the hedge twice a year, in spring and summer. The ideal time would be late June or early July, as the strongest growth is in spring. If you want to trim the Thuja hedge, you should really remove only the young shoots.
It is recommended to prune the hedge in a slanting way in order to avoid the hedge becoming bare due to lack of light (trapezoidal shape). To get a better branching, a heavy pruning (also only of the young shoots!) every 7 years is good. This will make the hedge denser.
Since thuja plants are quite undemanding, they do not really need to be fertilized. However, conifer fertilizer can be used if the color of the thuja fades or the plants take care. To do this, very carefully loosen the soil with a digging fork and work in the fertilizer. The additional nutrients will stimulate the plants to form new shoots. Compost, lawn clippings or leaves will also ensure that the soil around the plants is adequately supplied with nutrients. Thuja plants like fresh, air-permeable, slightly acidic to alkaline soil.
Thujas contain essential oils and the poisonous substance thujone mainly in the tips of the branches (by the way, it is also contained as a main ingredient in absinthe, but this comes from the plant wormwood, which also contains thujone). If the thuja plant is touched repeatedly, it can cause severe skin inflammation. If the poison is ingested internally, severe stomach and intestinal inflammation, cramps and kidney, as well as liver damage and epileptic seizures occur. The poison thujone can also have a lethal effect in larger quantities.
Therefore, please always wear gloves when you cut your thuja hedge! By the way, the same applies to the similar mock cypresses.