Pennisetum alopecuroides, which belongs to the Poaceae family, originally comes from Japan, Korea, China and Australia, where it grows naturally on sunny plains. It was introduced to Europe in the second half of the 20th century, where it enjoys great popularity because of its high ornamental value and frost tolerance. To the type of the lamp-cleaner-grasses belong still approximately 80 further, predominantly persevering types. However, Pennisetum alopecuroides and its varieties are the most common of all the species in our gardens. The botanical name Pennisetum is derived from the brush-like inflorescences of ornamental grass – it derives from the Latin words “penna” for “feather” and “seta” for “bristle”. For this reason, lamp cleaner grasses are also often called spring bristle grasses.
This persistent lamp cleaner grass forms a magnificent nest of leaves with arching overhanging foliage above which the filigree flower spikes appear in late summer. The leaf nest itself looks a bit like a small bush, since the leaves form an almost perfect hemisphere, and becomes about as wide as it is high, sometimes even wider. While the species is only about 60 to 90 centimeters high, some varieties, such as ‘Paul’s Giant’, can reach heights of up to 150 centimeters. The height of the inflorescences is measured here, the leaf nest is about 20 centimeters lower. But there are also dwarves among the lamp cleaner grasses, for example ‘Little Honey’ or ‘Little Bunny’ with a height of 30 centimeters.
The leaves of the lamp cleaner grass are very narrow and reach a maximum width of 12 millimetres. In summer the leaf nests of the species and the varieties are grey-green, in autumn they turn golden yellow. However, there are also varieties with exceptional autumn colours, for example ‘Cassian’, whose foliage is red, or ‘Hameln’, whose foliage has a very reliable strong amber colour. As a so-called “warm season grass”, the lamp cleaner grass sprouts late, but the ornamental grass is still very attractive in winter.
The lamp cleaner’s grass shows its splendid flower spikes, which remind optically of small bottle brushes or fox tails, only in late summer, but the flowers then form an eye-catcher in the bed or pot from August to October. Even after flowering, the flowers do not disintegrate immediately, so you can still enjoy them in winter. The flower colour varies from variety to variety. While the spikelets of the species are brownish and pinkish red, the variety ‘Cassian’ flowers ivory, the flowers of ‘Moudry’ are dark purple. If the summer is short and rainy or you live in areas with a harsh climate, it can happen that the lamp cleaner grass does not completely develop its characteristic flowers.
Location and soil
Lamp cleaning grass thrives best on nutrient-rich, fresh soil with good drainage. It also loves a warm place in the blazing sun. If the planting place is full of sunshine, however, you should ensure that the soil remains evenly moist, dryness can only be tolerated by well ingrown specimens. Compacted, heavy soils are not suitable because the ornamental grass has problems with waterlogging.
Planting and care
The lamp cleaner grass comes into its own best when you can see its pretty growth habit as a whole. Therefore you should plan sufficient distance to neighbouring plants when planting. It is not suitable for underplanting woody plants, as it cannot handle root competition and requires a planting place in the full sun. In the shade it would only thrive very poorly. The best time for planting is in spring. Heavy soils should be improved with sand or gravel before planting.
Pennisetum alopecuroides belongs to the “warm season grasses”, which means that it grows late in the year, forms its flowers later than many other ornamental grasses and also cuts a good figure in winter. This also has an influence on the care. So you should not cut this ornamental grass back in autumn, but only in spring – not only because it is also extremely decorative in winter, covered with hoarfrost, but also because the leaf nest protects the so-called heart of the plant and helps it to survive the winter undamaged. The grass can also be used by hedgehogs, for example, as quarters. Since it ages easily and then forms only a few flowers, you should rejuvenate it by dividing it every three to four years.
The best time for pruning the lamp cleaner grass is in late spring, just before budding. Here the ornamental grass is cut off about a hand’s width above the Soil.
Because of its attractive growth and pretty flowers, the lamp cleaner grass is particularly suitable for single use or for small groups in the bed. As a larger plantation its beauty would simply not really come into its own. Smaller and medium-sized varieties such as ‘Hameln’ are also ideal for pot planting, as long as the pot is large enough. For the ‘Hameln’ variety, for example, experts recommend an earth volume of at least ten litres, for the ‘Cassian’ variety the volume should even be at least 15 litres, and small varieties such as ‘Little Bunny’ can also cope with pots with a capacity of three litres.
As in a bed, you should also ensure good drainage when using it in a pot and insert a layer of expanded clay at the bottom as a drainage layer so that the water can drain off well.
Since the lamp cleaner grass feels most at home in beds in the open space, it is advisable to choose the plant partners accordingly. Beautiful pictures result for example together with high fat hens (Sedum Telephium hybrids), catnips (Nepeta), sun hat (Rudbeckia) and asters. The pretty flower spikes of the lamp-cleaner grass are also very suitable for cutting and radiate natural charm in late summer and autumn bouquets of flowers.
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Some varieties of Pennisetum alopecuroides are now available on the market, with growth heights varying between 30 and 150 centimeters, so you can find the right size for almost every garden and planting situation. ‘Hameln’: This medium sized lamp cleaner grass grows about 60 to 80 centimeters high and grows slightly more dainty than the species. In contrast to the species, its flower spikes are light green to white in colour. Besides, it blooms earlier and richer. Due to its compact growth, ‘Hameln’ is also suitable for group planting. ‘Moudry’: This selection from Japan is characterised by its strikingly broad, fresh green leaves and purplish violet flower spikes. In our latitudes it is a little flowering lazy and only blooms in mild areas. The flowering period does not begin until the end of September, which is a little later than for the other varieties. Moudry’ eagerly spreads himself and can therefore spread quickly.
Cassian: The Auslese, named after the German plant user Cassian Schmidt (head of the Hermannshof sighting garden in Weinheim), is characterised by a particularly rich flowering and a pretty autumn colouring. In August, it forms its ivory-coloured flower ears on overhanging stalks. Little Bunny: This dwarf variety of lamp-cleaner grass is a seedling of the ‘Hameln’ variety. It is only about 30 centimeters high and wide and is therefore ideal for pot planting and for planting in the front of the bed.
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The best way to increase the lamp cleaner grass is to divide it up in spring, but newly planted parts sometimes have problems growing. The species can also be propagated by sowing, most varieties only by division.
Diseases and pests
Diseases and pests are no problem for the lamp cleaner grass, but it reacts somewhat sensitively to waterlogging. Therefore, ensure good drainage and, if necessary, improve heavy soils with some sand or gravel before planting to make them more permeable.