Initial phase

Methods of management for herbaceous plants in newly planted woody plantings have often been described. Experiments have been carried out by many parties. Most of these experiments led to the conclusion that herbaceous plants can be planted in the initial phase without adverse effects on the young woody planting. Some have argued that this method is advantageous, if not in terms of the quality of the plantings at least in terms of cost. In the author’s experience, however, one should not establish herbaceous plants during the construction phase of woody plantings. Contrary to allegedly positive experiences, practice shows that if one keeps the soil free of herbaceous growth during the initial phase, woody plantings will reach closure more rapidly. Herbaceous plants that were sown or introduced spontaneously will always exert a degree of competition with woody plantings. If one eliminates this competition, one allows tree plantings to grow

quickly and achieve canopy closure. Another factor influencing time to canopy closure is the spacing of woody plantings. If spacing is not too wide—a minimum of 1.25×1.25 m—the planting may reach closure as early as the third year after construction. After this, the main focus of maintenance will be on the edges, where weeds have to be removed.

The description above also makes it clear that it is very important to start construction on a clean soil that is free from weeds. If one needs to get rid of weeds on a terrain that will be planted in the future, one can do well by sowing vigorous herbaceous plant ‘cover crops’. Once perennial weeds have been controlled, annuals, such as phacelia, lupins and such, will be beneficial since their dense coverage of the soil will prevent seedlings of many weed species from establishing. If, however, a decision is taken to establish herbaceous plants at the same time as trees and shrubs at planting distances greater than 1.25m, one should expect canopy closure to take six or eight years. During this prolonged period, a certain degree of maintenance will still be necessary if more competition – intolerant species are to persist. Only the woody species that are more or less resistant to competition—such as ash or field maple—can reliably hold their own against weeds such as sow thistle or bindweeds. This is especially valid on highly fertile soils. The costs involved in keeping a woody planting weed-free for three years usually match those of the longer period of maintenance involved in the latter example, whilst the quality of the result in the former is considerably higher.

Another important guideline for the initial phase is that one should start pruning early. By keeping the young planting completely free from weeds, results in quick growth. On rich soils this means that one has to start pruning at the end of the third growing season. It will mainly be limited to cutting back to the lateral shoots of a number of individuals of species that will later form part of the shrub layers. These may include hawthorn, hornbeam, field maple, oak, common maple, holly and yew. When these are cut back to laterals early on, they will start developing more strongly in a lateral direction. The prunings that are produced must, however, be removed. If they are left lying where they fell, this will make maintenance in later years more cumbersome. By the fourth year after the initial planting, one should also start thinning: fullscale maintenance pruning commences. So as to be able to develop well, every tree and shrub needs sufficient lateral growing space. By timely providing for this space, we can prevent the emergence of a planting of stakes or a forest of masts. Shrubs should not just be cut back hard, allowing re-growth after which it will reclaim its original space, but some of them should be removed completely. The space that is thus created can subsequently be filled by the remaining shrubs, allowing them to keep developing and growing in size.

In large-scale plantings—for instance, at town edges or in rural areas—one may also consider using the method of bark-ringing for thinning. It consists of locally removing a ring of bark, causing the tree to die on its trunk. Dying on the trunk has a number of advantages:

– no prunings are produced, resulting in much lower pruning costs and also because one

does not incur costs for shredding and or removal

– gradual destruction of the wood that is produced, causing less disturbance

– an increase of the ecological variety—dead wood is an important environment for all

kinds of plants and animals.

The method has some disadvantages as well:

– the need for careful execution; in young trees and shrubs, the bark should be removed just above the root neck, i. e. just above and below ground level, or else re-growth will occur—in older trees re-growth will not take place, even when the bark is ringed higher on the trunk

– in older, larger trees, the total decay process may take several years.