Polystichum aculeatum hard shield fern
Polystichum
The genus Polystichum is one of the largest and at the same time one of the longest studied groups of ferns. Botanists currently recognise around five hundred species, distributed almost worldwide, from the temperate regions of the Northern Hemisphere to mountainous areas of the tropics. The greatest species diversity is concentrated in East Asia, particularly in China and Japan. It was here that polystichums evolved over millions of years in relatively stable forest ecosystems, a fact indirectly supported by fossil finds of ferns with very similar frond structures dating back to the Tertiary period. The genus belongs to the family Dryopteridaceae, and its systematic delimitation represents one of the most complex chapters of fern taxonomy, as it includes numerous transitional forms, natural hybrids and apomictic species reproducing without fertilisation. The first formal description of the genus was published by Albrecht Wilhelm Roth (1757–1834) at the turn of the eighteenth and nineteenth centuries, at a time when European botany began to study ferns not only as part of the forest understorey but as an independent and evolutionarily remarkable group of plants.
The name Polystichum itself is derived from the Greek words polys and stichos, referring to the dense, regularly arranged rows of sori on the underside of the fronds. These are characteristic of the genus and, on closer inspection, appear almost surprisingly geometric. In the nineteenth century, polystichums became part of the phenomenon known as pteridomania, when ferns quite literally took over European gardens, glasshouses and interiors, and were collected with a passion more commonly associated today with orchids or succulents. Thanks to their evergreen fronds and ability to thrive in shade, many species entered garden cultivation before they had been thoroughly studied botanically. Although it might seem that a genus with such a long history has little left to reveal, modern molecular methods show that research into polystichums is far from complete, and that their relationships and the origins of individual species are still being reassessed.
Hard shield fern is an evergreen species of fern found in many locations around the Globe. Being so ubiquitous many botanists from several countries where it wildly grows presume it originated there. You will find it in most elevated parts of Central and North Europe, Caucasus, Far East and Central Asia, even North Africa, and N.E. USA and Canada.
It produces 30-90 cm long, bipinnate fronds composed of lance-shaped, acute leaflets (pinnae). It can be distinguished from other polystichum ferns by the last upper pinnae that is up to twice as large as the others. They are dark green and very glossy which makes this fer an attractive companion plant in mixed borders as well as containers. The taxon received the Award of Garden Merit by the RHS (Royal Horticultural Society of the United Kingdom).
Polystichums are woodland ferns suited to shade or partial shade, and to humus rich, well drained soils with a good supply of organic matter. They are not sensitive to soil pH and grow well in mildly acidic to neutral conditions. They do not tolerate waterlogging, prolonged drought or heavy, compacted ground. An organic mulch of leaf litter or fine bark is beneficial throughout the year, helping to maintain stable moisture levels and soil structure. In ordinary garden soils, which lack the natural woodland microflora, the use of a mycorrhizal inoculant at planting is advisable, as it significantly supports establishment, stability and long-term vitality. It responds well to feeding. It is hardy to min. -34°C (USDA zone 4) and allegedly root-hardy down to -40 °C (USDA zone 3).
Last update: 03-12-2020;27-03-2026
