Evergreen trees are of great value in gardens, parks and public green spaces. They provide structure, colour and shelter throughout the year, especially during the winter months when deciduous trees are bare. Planting and transplanting evergreen trees, however, requires extra care. Unlike deciduous species, they retain their leaves or needles and do not enter full winter dormancy. As a result, they are more sensitive to weather influences such as wind, sun and frost. In wet soils, light frost can sometimes even be helpful during planting operations, as it improves ground accessibility. In such cases, keep the planting hole frost free by covering it temporarily. With the right planning, careful execution and proper aftercare, evergreen trees are a sustainable and valuable addition to any green space.
Tree species such as Quercus ilex (holm oak), Q. suber (cork oak), Prunus lusitanica (Portuguese laurel) and Ilex aquifolium (holly) remain active in winter because they retain their leaves and therefore continue to transpire. Conifers are also susceptible to winter stress despite their robust appearance. Species such as Cedrus deodara, Sequoiadendron and Chamaecyparis can suffer from desiccation when exposed to a combination of wind, sun and frost.
Common mistakes when planting in winter
Planting during severe frost should be avoided. Not only is the soil difficult to work, but root balls and roots may be frozen, which seriously hampers root development. During winter storage, protection of the root ball is essential. Covering it with hessian, straw or leaves prevents desiccation and frost damage. When planting in snowy conditions, it is important to clear snow from the planting hole. After planting, snow can actually be used as an insulating layer to prevent further cooling of the soil.
- Lack of aftercare is one of the main causes of failure. During the first three to five years after planting, watering, checking anchors and, if necessary, formative pruning are crucial.
- Planting too deep is a common mistake. Most fine roots are located in the upper part of the root ball. If the root ball is placed too deep, oxygen deficiency develops in the root zone. After planting, the top of the root ball should be level with or slightly above ground level, especially in loose soils that may still settle.
- Planting in wet or water filled planting holes is also not recommended. Lack of oxygen leads to root death and poor regrowth.
Cold stress and desiccation
Because evergreen trees retain their leaves, they continue to transpire even in winter. Wind and sun intensify this transpiration. At the same time, at low temperatures the tree is barely able to absorb water. This leads to so called cold stress: the tree dries out while the soil appears moist.
The correct lifting time
For evergreen oaks such as Quercus ilex and Q. myrsinifolia, the correct lifting time is crucial. This is at the end of winter, just before the start of new growth. As soon as young shoots become visible, the tree is active and the risk of establishment failure increases sharply. Here too, the rule applies: plant as soon as possible after lifting and limit transpiration wherever possible.
Wind load and anchoring
Evergreen trees catch more wind in winter, especially when leaves or needles are wet from rain or snow. This increases the load on the trunk and root ball. In avenue trees this load is concentrated on a single stem, while multi stemmed trees distribute the forces more effectively. Good anchoring during the first years is therefore essential to ensure stability.
Bare root planting and protection
For bare root plants, planting during frost periods is not recommended, as the risk of desiccation is too high. Fine hair roots die off quickly when exposed to dry air. Protection against desiccation and frost is therefore essential. Watering immediately after planting ensures good contact between roots and soil and prevents air pockets, which is not possible during frost.
Mulch as protection
A mulch layer of organic material offers many benefits in winter. Mulch acts as insulation, reduces evaporation, protects against frost and improves soil life. In addition, it suppresses weeds in spring. Always apply mulch in a thin, airy layer to prevent oxygen deficiency in the soil.
Evergreen trees provide colour, structure and shelter throughout the year, but require extra attention when planting. Because they retain their leaves, they continue to transpire in winter and are sensitive to wind, sun and frost. The correct lifting time is at the end of winter or in early spring, followed by rapid planting to prevent desiccation. Common mistakes include planting during severe frost, planting too deep, waterlogged planting holes and insufficient aftercare. Cold stress can occur when transpiration continues while water uptake is limited. Good anchoring, protection of the root ball and adequate watering are essential. Conifers and bare root plants also require extra care. The use of mulch helps protect against desiccation, frost and weeds. With careful planning and aftercare, evergreen trees can establish successfully and add long term value to green spaces.
