Decorative flower fronds that rustle gently in the wind, a stately growth habit and filigree, matt green leaves characterise the pampas grass. For some years now, ornamental grasses have played an increasingly important role in modern garden design: as discreet intermediary elements in perennial beds, loose planting groups or impressive solitary grasses. Their popularity is sometimes also explained by the fact that they are quite uncomplicated to care for. In the case of vigorous grasses, it is particularly important to cut back the old inflorescences in spring. How should pampas grass be pruned to guarantee numerous flower panicles year after year?
Pampas grass belongs to the sweet grass family, the Poaceae. It grows in dense clumps and sometimes reaches extremely impressive heights. The conspicuous spikes of the grass give it its special ornamental value, the long inflorescences usually tower above the leaves many times over. They can be admired in the garden for several months, even when they have already faded.
The species most commonly found in the ornamental garden is Cortaderia selloana, the American pampas grass. Depending on the variety, there are differences in growth height, shape and colour of the flower fronds as well as flowering time. Good to know: Pampas grass is dioecious, which means that there are both female and male plants. The flower fronds of the female plants are larger and more numerous, which is why they are used much more often in the ornamental garden.
Type and variety have no significant influence on the care measures, so every pampas grass can be pruned in the same way.
What is the effect of pruning?
The growth in clumps makes the pampas grass an ideal specimen grass because it always remains compact and usually grows evenly. However, the growth habit also makes annual and quite radical pruning necessary. Otherwise, the new shoots will sooner or later no longer have enough space. In addition, rot can occur if old and new shoots stand close together for years. When pruning, mainly the old inflorescences are cut back, because the pampas grass is evergreen. However, it can happen that leaves also dry out over the winter.
The inflorescences usually wither at the beginning of autumn, but do not fall off by themselves. They do, however, serve another purpose: over the winter they are left standing, together with the leaves, loosely tied together with jute string or twine, as a natural winter protection. Tying also prevents rainwater from collecting in the centre of the plant. The pampas grass is sensitive to moisture.
Pruning pampas grass: This is how it works
The right time
Because the withered inflorescences and leaves are left standing over the winter, the pampas grass is not pruned until spring, at the earliest when no more frost is expected. As the weather varies from year to year, it is not possible to give an exact date for pruning. Instead, you should keep an eye on the new shoots. If the new shoots have already grown about 15 centimetres, you can prune the dead shoots just above the fresh shoots. A dry, cloudy day is ideal for pruning pampas grass. By then, the old shoots have usually already lost stability and are leaning to one side.
Avoid autumn pruning
Pampas grass should definitely be pruned in spring. As the inside of the stem is hollow, water often accumulates in the cuttings. In damp and cold autumn weather there is a risk of rotting and during the winter the cold-sensitive pampas grass is at risk of frost.
In the case of a grass with a manageable diameter, the band that has held the culms together over the winter may be left on during pruning because it facilitates even pruning. However, depending on the size of the clump, it may be necessary to cut back several clumps at a time. Sharp rose shears or hedge clippers are used for pruning. It is important that the tools are clean and free of possible bacteria or viruses.
Important: Always pay attention to the fresh shoots. So that it is not shortened, prune a few centimetres above it.